# [SOLVED] 95 Chevy S-10 4.3L TBI - Idle troubles



## dgoad

I would like to ask some of you to take an educated guess at this problem(s). My son's has a 95 S-10. Was running great, until one day a couple of months ago, it started running really rough at a red light ( as he tells me ) and he had to work the throttle to keep it running and then about a block or two later it quit and hardly would start. When it does, it will not stay running well even with throttle work. My son was told by one of his buddies that he thought the Catalytic converter was plugged up. So, my son took it off only to find that it was not plugged and the truck still has the same trouble. So, he had it towed from his house to mine. I know! I Know! Anyway, I got a chance to help him with it the other day and boy what a job. I will tell you that this truck has a little over 200,000 miles on it and the only thing that has been replaced was the altenator a few months back. Yes, it is in need of some help. Anyway, I started by looking for vacuum leaks and I found a couple and replaced the fitting and hose. The engine is still loping really bad. I read the engine codes and got an EGR and RICH code. Looking at the Throttle Body I noticed that both injectors were dripping. So, basically I rebuilt the TBI. New injectors, fuel pressure regulator, cleaned the IAC and the ERG valves. Installed new plugs, wires, cap, rotor, fuel filter, and O2 sensor. I checked the fuel pressure and it is reading 11psi down to about 7psi. The pressure moves down and back up slowly as you race the engine and basically is pretty stable most of the time around 9-10psi. I was told that this is normal and that while the fuel pump is old ( and I will more than likely have to buy one of those too! ) it is still working and it should not be what is causing the running at idle problem. I am saying an idle problem. I figure that when I find what is stopping it from idling correctly, I will be able it fix all the problems. ( well maybe not ) I reset the codes and now I have none showing. Computer does show that it is in OPEN LOOP MODE and O2 Sensor shows RICH and while working the throttle and watching the code meter, the reading will move from RICH to LEAN and back to RICH again. While all of this has helped the engine somewhat, it still barely idles and it still lops really bad. Throttle aceleration is smoother ( not a clean smooth note by any stretch ) when going up with NO backfires up or coming back down, but the engine still hunts, misses and lops. There are only a few things that I think that I might have missed, other than my brain, and I might not be able to find it either. I have not looked at the igniter module for the ignition and I don't know if this could even cause this kind of trouble. I have not done a compression check. The head gasket comes to mind, but I have no water or oil issues inside, outside or otherwise. And come to think about it I have not checked for water in the gas. But, that would have to be a lot of water. We have burned, spilled, sprayed and or pumped out and use several gallons during our fuel system adventures and the tank is still half full and problem is still there. Anyone with any insight and comments other than "just shoot it" , I would like to hear your ideas and they would be appreciated. Oh, and I did kick it in the right door panel because it got in my way, still no luck. Thanks.


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Evening dgoad, it is not uncommon when engines have vacuum leaks to find exhaust valves get a little burned, which could well be your problem.
I would suggest a comprehensive compression test with all plugs removed recording all pressures and then repeating the test on each cylinder after adding a few CC's of oil down each plug-hole. Once again record pressures.
Any notable variation spread initially may tell you something and any reasonable variation between non-oiled and oiled readings would suggest rings may have a problem.

Low fuel pressure can also cause this kind of effect, what is the book pressure for that machine?
I wouldn't expect any large spread with the engine running, it kind of suggests to me that the fuel availability is a bit short.

Regardless of any suggestion it sounds like you are going to have to spend on the thing. 

Isn't it exasperating when one of these things won't idle nicely!

Cheers, qldit.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Thanks for the reply! The book that I have states the fuel pressure to be between 3 and 12 psi and that movement is normal. I have never heard of such thing, but there are a lot of things I have never of, this could be one of those. I will be doing a series of commpression checks today to see what is up with that. Thanks.


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## Midnight Tech

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Does that truck have the vacuum or electric EGR valve? it kinda sounds like the EGR may be stuck partially open...dumping burnt exhaust gases in at idle and low speeds will make one run like you describe.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Hello MT,
The truck has electronic ERG. Here is an update. I ran compression tests and all cylinders except #5 read around 105 - 110. Number 5 reads 95 +- 5. All plugs are new with only about 5 mins on them. When I pulled them to do the compression test they all are lightly coated with black soot. RICH, RICH, RICH. I put it back together again and we cranked the truck and I was looking at the injectors while it was running ( sort of ) and I got the idea that it looked like the injectors are spraying too much fuel into the TBI. So, I pulled one of the power connectors from one( the left one ) ( as looking from the front ) and stopped it from spraying fuel. Guess what? The engine runs almost perfect on just one injector. I did a swap with each injector and saw no difference as to which one was hooked up. It is now, more than likely, LEAN, but it will run up and it sounds pretty darn good. Question? This looks to me to be the car computer. Is this a reality? Can the car computer really be putting out the wrong data to the injectors? Or can the injector driver ( electronic switch ) to which the computer sends the signals be bad ( it is still inside the computer case ) and the Computer states that it is putting out the correct thing. My Code reader is not showing any codes. Thanks


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## Midnight Tech

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Wild shot here...but check the coolant temp sensor...it might be telling the computer wrong.

If you can obtain a junkyard computer of the same year, transmission, and engine you might give it a try...just disconnect the negative cable before pulling the plugs on the computer.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Hello MT,
Not giving up here, I have more info. I placed the scan tool back on and noticed that the MAP is now generating a high voltage error code. I looked at the realtime running value of the MAP output and I was getting about 4.x volts at the rough idle point and as I ran the engine up I was able to get the voltage to about 2.2 volts or so. The voltage is moving through the RPM range, however, my manual states that the voltage should be around 1.6v at idle and increase to around 4.x volts at full throttle. This is opposite of what I am getting. In a way though, it makes a little sense. If the CPU is being told my the MAP that at idle I am asking for full RPM fuel and at full RPM it is asking for idle fuel. Strange, I wonder is the MAP sensor can do this. I have not changed this part, yet!
More to come, I'm sure or that. 
P.S. I did see the coolant temp in the scan tool and it was reporting correct and it was moving hotter as I ran the truck. 
Thanks.


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Morning Chaps, yes that whole thing sounds very odd, I must say I have never tried running on one injector, that is good to know for a trial.

The system should be on closed loop mode at start so I doubt whether a lot of the sensors should really have effect.
It certainly sounds like it is substantially overfuelling.

I must agree trying another computer would be my next thing, it sounds like the start program is really "whacked".

This is just a guess, but base injector timing is the computer.

I would be inclined to remove the computer take the cover off it and have a close look at the printed card for any obvious damage or component failure, quite often it saves a lot of mucking around.

Edit. That overall symptom and the idling is not that far from a "limp mode" kind of effect.

Cheers, qldit.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Another Update,
It looks like internet and my repair book is wrong on the subject of MAP sensor voltage. I was told that the MAP sensor puts out 1.2 - 1.6 volts at idle and around 4.2 - 4.5 at Wide open. This data is wrong. I found a chart that states the MAP sensor will return about 4.5 volts at 0-1000ft of pressure altitude and work its way down to about 2.2 volts at 10,000ft. That means that before idle ( car on ) the Baro and the MAP should read almost the same and since I am at sea level we should see about 4.x volts. Today the Barometer read 29.83 and the MAP read 29.47 and about 4.1 volts. Start the engine and the MAP sensor shows a small vacuum down to 27.xx and the voltage goes to about 3.9 +-. When the engine RPM is raised the MAP reading goes down into the 19.50 range with a voltage output of 2.6 +- or so at high RPMs. This would tell me that the manafold pressure is -10psi with respect to the outside air or 10psi of vacuum. I was getting a MAP sensor HIGH voltage error code. My old sensor was putting out about 0.5 volts too high or around 4.7 volts at ( ON ). I thought that the MAP was bad and today I changed it. The output voltage is lower and the error code is now gone, but the engine still runs and hunts very bad on idle with both injectors plugged in and runs 85-90% the way it should on only one injector. I guess I am back to being lost. I see that the computer is telling me that the injector ON time is running around 3.8 msec or so. This does change with throttle application. Question? Since I know that different injectors ( they make many sizes and flow rates ) flow more or less fuel with the same pulse width, where would I find out what flow rate the original injectors where to output( lbs/min ) and where is it written what pulse width should the cpu be sending to the injectors at idle. The engine did have leaking injectors before I changed them, but I am thinking that maybe the flow rates are different between the two sets. Maybe not. What I do know is that there is too much fuel spraying into the engine at idle when both injectors are pluged in. Also where can I find a list of data or specifications for all the sensors, on a normal good running 4.3L engine. What should they read at idle? Anyone got any ideas about where to find this stuff. I have spent hours looking on the internet for it and I can't seem to find it. Anyway, I still want to see about the computer also. I am still looking for anyone that might have any ideas, I am all ears. I will try to post any updates, as they might help anyone else. But this is getting pretty stupid and I am almost sure that the fix has been missed or it is the computer and I have not gotten there yet. I also re-read the fuel pressure specs and I think I mis-understood what it was saying. It should have been 13psi - down 3 to 10psi, not 13 down to 3, but I am still marginal there maybe a little low at full throttle, so I will have to fix that at some point, don't think it will effect my idle problem at this time. Thanks for your time and help.


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Afternoon dgoad, gee you have really gone into this, I never get that deep.
If the injectors have a problem I set them up on a bench with a bit of fuel pressure and observe how they perform simply by toggling a simple switch, I am really only interested in seeing them spray nicely and open and shut off properly.

As far as I am concerned the open loop situation with the O2 sensor should alter timing when running so the circuit should self regulate.

I only replace injectors with identical items, so I haven't any experience with interchanging different types. 

I have seen computers in a limp mode without any indication that is what had happened, so I really don't trust any codes on an obviously kaput system.

One chap had changed the MAP sensor several times because of error codes where in fact the actual computer was the problem. 

It happens that you may see MAP sensor error codes and when you replace the computer those codes don't show, so it can be very confusing.
I suspect the voltage regulator in the computer can cause this effect.

Sometimes I have found the area of the voltage regulator and board cooked, that is why I like to take the cover off and actually visually check.
One fellow had spent many hundreds of dollars on his machine to various repair places and in ten minutes I had the computer out and cover off and pointed out, "this might be your problem"! one board area was charcoal and tracks were damaged.
So I never get too involved without having a visual look at constant problem machines these days. 

You sure are going through a learning experience there, keep the test info coming! 
It is really stirring up my grey matter!

Cheers, qldit.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

hello qldit,
Yes, the computer is were I am going. I have checked the 5v reference voltage from the computer and it is ok. I did replace both injectors with two identical replacement parts from autozone. Well really three of them. One of the first two was stuck ON. It would flow fuel just by turning the key ON and without the connector being plugged in. I took it back and got another one. Yes, it should be self correcting and with one injector plugged in I am getting a msec timing pulse of 3.8msecs. The engine is lean, but it is close to right. When I plug in the second one the pulse width only drops to about 3.1 or so. this goes to both injectors. It seems to me that if one is almost good ( for idle ) at 3.8 then two would drop it down to around maybe 2.0 for a combined effort of about 4.0 worth of fuel. Anyway, I am going to find a way to get the computer out from behind and above the glove box and I will remove the cover a see if it looks bad and I will more than likely replace it anyway. I don't think I have any choice. I am already out about $300 what a little more? I will post again. Thanks.


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## Raylo

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Interesting thread. I have been reading it even though I have a 1994 S10 p/u with engine code W (CPI) that has a different fuel injector system.

But I did have a similar problem once upon a time. Turned out to be a sticking EGR valve. I replaced it and all has been good. When it happened it was very hard to keep the truck running because dumping a large amount of exhaust gas into the small idle air flow is obviously bad. I saw you replaced the EGR but it might still be worth doing a test by visually verifying that it is shut then removing the vacuum source to make sure it doesn't open when you start the engine.

The other time I had a similar problem was on my Z28 when the air intake elbow came loose on one edge where it attaches to the throttle body allowing a lot of unmetered air into the motor, which reduced air flow over the MAF and totally threw off the computer and mixture.

Anyway, these are a couple of "simple" things to look at. I'm not sayng your trek down the bad PCM path is wrong, it's just that in my experience 99% of the time it turns ot to be something simple.

Good luck. I'll keep reading and hope to see you get this resolved soon.


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Evening Gentlemen, yes it most certainly is interesting, one point of interest is that I would have expected it to be a "closed loop" kind of config at initial start and if that were the case it would be expected to be a little towards rich but follow a pre-programmed arrangement.

The original problem onset "it started running really rough at a red light" kind of indicates to me that it was operating OK until it became stationary in that instance, coupled with the alternator being replaced shortly beforehand, (I kind of suspect that the dreaded "jumper leads" may have even had some possible involvement, as a guess) but circumstantially it has had an electrical problem of one kind or another previously, and this problem suddenly arose.

It will be interesting to see what the outcome is, the old adage applies that "you always find the problem in the last place you look"!

I am not familiar with that particular computer system but it is reminiscent of some of our Bosch systems that failed in a "limp mode" (kind of get you home mode where the injector timing is not really controlled, a ***** to start and runs rough)

I am probably wrong but it is reminiscent of an experience I had and the circumstances are very similar.

Cheers, qldit.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Hello Gents,
Raylo makes some good points, but my engine has a MAP sensor instead of the newer MAF ( Mass Flow vs. Atmospheric Pressure ). My MAP sensor just has a small hose attached to the intake manifold. My engine also has an electric servo driven EGR valve with NO vacuum attached. I am still getting an error code about the EGR valve and I will have to replace it at some point, however, I did take it off and clean it and manually shut the return gas valve. I put the unit make on and I left the power control connector unplugged so it would not move. This made no difference in the engine problem. I did order a CPU today. I did take the cover off of the old one. I did not see anything that was out of place with the unit. No burnt or colored areas. Nothing. Tomorrow or maybe Saturday, I am going to take my scope outside and put it on the injector leads and see what the pulse width I am really getting at the injectors. This is more of a question in my mind than any thing else. I want to see if it is the same as what the scan machine says that the CPU is putting out. 

Yea, the truck was running and the alternator went out back in March. A new one was installed. That was the only and I mean the only part on this truck ( other than tires and brakes ) that is not original. It has almost 290K miles on it. I know, but it's true! I don't know if he used jumper cables or not, maybe so. That can cause electical troubles with computer controlled engines. But, it did run for several months after the altenator change out, I guess we will see next week. My son tells me that over a several week or maybe a month time frame the engine was starting to not quite run right. He noticed that if he stepped on the gas it would bogg down for a second or two before picking up speed. He also noticed it starting to idle a little rough, talking here about a miss or two every 10 seconds or so. The day in question he told me that he drove the truck about 5 miles to work and that about 5 or 6 blocks away it started really running rough and that he had to work the throttle to keep it running. Then at one of the lights it quit altogether. He had a hard time getting it cranked again and he had a hard time getting the rest of the way to work. Remember now, since it has been here I can say that the engine is and has been running RICH, very RICH. His original injectors were dripping down the middle of the spray on one of them and down right leaking with a small stream in the other one. It may ( I am guessing here ) have been that the injectors just got to the point that the CPU could not help over come the fuel anymore and that is why it runs so bad. The plugs that I pulled out, original and in bad shape, were not oily. They all were just jet black with a black power like dust all over. The new plugs, that have maybe 10 minutes on them, look the same. It now seems to me that the engine had/has a RICH fuel problem and I thought that new injectors would save the day. The fact that the engine is still RICH troubles me and I hope the CPU will be the answer. Later guys and gals, more to come. And the CPU should be here middle of the week. As always, if you run across any info that might help answer the big question, please pass it on. Later.


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Afternoon dgoad, is there anything in the info you have relating to "limp" mode for that computer?

Also does it contain a config chip that you may need to swap across to the replacement item?

I had to laugh when you mentioned you had a CRO out on that engine, the last time I used a CRO in the field, I was developing a voltage regulator system for a jet engine generator, and it operated perfectly on the bench but not when mounted on the running engine.
I was using an optical sensing system and eventually realised the thing was susceptible to external infra-red, so that job ended up being a real headache.
Alternators appeared shortly after that so the whole exercise was really never applied apart from that prototype! 

I can imagine you with leads everywhere doing that, at a guess I suspect you have an electronic background, sounds almost like TV stuff! LOL!!

Funny thing, I was involved in the industry when transistors first began being used, and naturally they were rapidly appearing in car radios, then a local vehicle manufacturer made one range of motor vehicles that really killed these early radios, the only difference was that in this particular vehicle model the radio was mounted above the glove-box directly under the dash top, which naturally was metal and painted flat grey/black.

We placed temp sensitive strips on one of these radios and left it the vehicle parked in the sun on a mid-summers day, naturally the radio died as was expected.
When the temp strips were inspected they had all discoloured, including the 130 deg C strip, so that was quite telling!!! 

Circumstantially although transistor engineering has evolved substantially I am surprised to hear you mention the location of that computer.

Cheers, qldit.

Cheers, qldit.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Hello qldit,
Yes, I have been around the block a few times. I am an engineer with Rocketdyne. We have been owned by several major companies over the years. Rockwell Int, Boeing and now Pratt Whitney under United Technologies. I have been working on the space shuttle rocket engine program for the last 30 years. I think I still remember transistors. I was bread boarding motherboards ( they did not have any at that time, late 70's ) with the 6502 and the 8080/8085. I have designed a lot of custom stuff we use in the space program. I have had the experience on not only working on the design or the only one on the design, but also working on building and packaging the electronic equipment. I even got written up in the NASA Tech Briefs may years ago for a little invention of mine. We had two computer acquisition system that were running in real-time and only had a few milli-seconds of processor time available to fetch more data. They just could not handle the extra task that was needed. So, I invented these two cards that plugged into each of the computers with a cable attached between each card. These card's only overhead to each system was a little power. The card in one of the systems literally watched for a new data frame coming across the bus and stole it without the first computer knowing about it. It then send the data to the other card in the second computer. This card placed the data into a block of memory that the second computer had access. The code was changed slightly to let the second computer fetch this block of data and it was on its way. These cards had small micro controllers running the show, but the other two systems did not have to stop what they were doing. When they needed the data it was there and they did not have to go get it. That was pretty cool stuff in the mid 80's. I have been blessed with a very good job and great people to work with. I think I have done about all stages of the job from electronic tech, lead tech, programming and instrumentation engineering. On the side, I worked on and repaired a lot of commerical ( ALTEC etc. ) sound amplifiers and band amps and things. I still enjoy working on one every now and then for the church or local business or a friend of mine. But, now it is just keeping the kids stuff running. Computers, Cars and fixing the house keeps me pretty busy. That reminds me that I should receive the car computer on Wed or Thursday.
I was going over the last thing my son remembers doing with the engine and low and behold he told me that he did have to jump the truck several time and that one of the guys he works with did indeed arc the battery pretty good when he dropped the jumper wire. He thinks that some of the trouble started shortly after. He says that he really did not drive it all that much after that because of a car pool, but that it was going down hill. 
I am going to put the old computer back in for a couple of minutes in a couple of days and put my oscilloscope on the injector wires and read them for my own data reference and then I will put the new CPU in and hope like heck it runs correctly. 
I will post again in a few days. I just learned that his other ( I think a small Toyota ) car just crapped out. He thinks it is a head gasket. Now, it is also parked in my driveway leaking oil all over the place. I guess I should just put up a sign and advertise or set up my own firing range. Thanks,


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Evening dgoad, I am in awe, It is funny isn't it the way you end up being the family and friends Mr. Fixit!
I have had a lot of experience with the older P&W Jt-3 & JT-9 series, GE's and RB211's but that is all history now.

I would have loved to have been involved with rockets.

Things always break in a series (usually 3) sounds like you have a head-job on your hands next, if it is a front wheel drive you will really enjoy that!! LOL!!
I hope you have a nice set of metric tools there!

From memory that computer "limp mode" virtually results in simply dumping fuel into the system and there is not much injector timing involved, I think the whole idea was simply to alter the air butterfly to try to get you home kind of thing, it will be interesting to see what you find. I never bothered to check it.

I found in BOSCH computers it didn't give a code, I suspected the rest of the system was isolated somehow as if it were running normally.
Obviously you are thinking similarly. 

I must say it is a pleasure meeting you, in view of the possible jumper lead escapade it becomes more probable the computer will fix it.

I usually get them from auto wreckers, they have amazing reliability.

Cheers, qldit.


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## paininthebrain

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Howdy dgoad,
I have been following your conversation because I have been working on a 1991 Chevy PU with a 4.3tbi. It also barely ran and I also checked evertthing you have. I broke down and took it to a friends shop. He new what it was with touching the truck. It was a small piece of fuel line in the tank for the pump. The line had a small hole in it, just enough that the injectors were not getting enough pressure. I hope this helps you.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Thanks pain,
I just got the new computer in and I will be working this issue over the weekend and I will post shortly.


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## dgoad

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Ok, here is the final words on this subject. The engine computer solved most of the trouble. The engine still did not run that good with the new computer, however, it was running and acting mostly normal or mostly below normal. I did not replace the coil at the time that I replaced the plugs, wires, cap and rotor and even though I had spark, it looked more yellowish or something that did not look bright blue. So, I changed the coil and all of the engine troubles are gone. It runs great. 

As to the timing pulses to the injectors. The old CPU was putting out pulse that are very close to what it said it was doing. It was asking for 3.8 - 4.2 msec pulses at idle. Remember, I was getting too much fuel flow with both injectors hooked-up and it almost ran good with only one injector. Well, the new CPU is asking for 1.6msec pulses and it runs right with both injectors and the fuel flow is minimal at idle as one would expect. 

What was learned from all of this? Well, parts do where out and should be changed from time to time before all crap out at once. This truck was equiped with the original spark plugs, wires, cap, rotor and coil. I should have changed them all, period. The O2 sensor needed to be replaced. The MAP sensor does not appear to have need to be replaced, as the old CPU reported both as bad and the new CPU has NO error codes. The IAC and the EGR valve where stuck and dirty just like the whole TBI. I cleaned them up and freed the pistons on the valves and they both are working and moving just fine. This is the opinion of both myself and my scan tool. The old injectors were leaking. You can tell by the little streams coming out of the bottom of the injector along with the normal spray pattern of fuel. The little streams should not be there. They needed to be replaced and so they were. The fuel pump I believe will strike at any time. While it is to produce 13psi and is allowed to fall to around 10psi at full throttle, this one is producing around 11psi and will drop to around 8 or 9 when throttled up. But, for now it is getting by. I did replace about 4 foot of several different sizes of vacuum hose and a couple of fittings. Almost all had cracks and tears. The CPU was more than likely taken out when jumper cables were used to jump start the truck and they were let to arc. I am now learning that the truck started going down hill after that event.

So, here we are after several weeks of fun with about $500 bucks worth of parts and priceless patches of hair missing, but I have my son's truck running again. I think the water pump and/or the fuel pump will fail shortly, but what the heck, he will soon be back in his own vehicle. I say soon because, I just found that when you place your foot on the brake pedal that the engine runs poorly again and its idle speed races up to about 1500 rpm, classic vacuum leak stuff. I pulled the vacuum hose off of the power boost unit and sealed it with my hand and it does not do this anymore. I guess it is back to the parts store for a power boost unit and I guess a new set of brakes while I'm at it. If is was not for keeping your kids in vehicles, what would dads be good for, right? 

Thanks to all that sent replies to help with my ordeal. I checked out and looked at everyone of them. I put a lot of words into this post and my others so that maybe someone might be helped by something that was covered here. There is a lot of stuff here and we replaced a lot of stuff. All but the MAP sensor was needed and every item made a difference, even if a small difference, in the way the engine ran. Even now faced with a major brake job that will cost another couple of hundred dollars, the truck will live again and it beats the hell out of a car/truck note, not to mention insurance and tags.

Paininthebrain, I too had that problem several years ago with small chevy. Yes, when the fuel pump pumps the fuel right back in the tank it will not make the correct amount of fuel pressure for the TBI system or injectors. Not knowing what is wrong and how to fix it can be a hardship. I have felt your pain.

Good luck with all of your projects and many thanks to those that are willing to share a little part of their knowledge and interest with myself and others.

DGoad


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## qldit

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

Good Morning dgoad, my compliments to you, you most definitely are an "ace" with applied logic and experience!

Your experience feedback will certainly give others clues as to how to interpret problems and also reinforces my own personal limited experience.

And yes, reference the brake boost leakage, isn't that always the way it goes!

From my own experience any use of battery jumper cables should be avoided, I get criticism whenever I insist on removing a flat battery and charging it or replacing it, when those kinds of problems happen.

And yes again, your finding with MAP sensors being interpeted as problematic by codes is inline with mine when in fact they are OK.

I don't really give much notice to codes, but simply consider them as "possibly assistive" 

You most certainly had a crash course in these systems!

As you are aware, the spark voltage is always negative polarity, but if you ever get a chance to really get up close and personal with it, you will observe a fine blue centre to the arc with a trace of jagged yellowish (fire) on it's outer edge.
If ever you try this though, use a conventional ignition (points system) in case the electronics in the system may be adversely affected.
(use a plastic rimmed magnifying glass, not a metal rimmed one like I did!!)

By the way, I had a simple brake job recently, just change the pads, when I compressed the caliper pistons discovered leakage in their seals, then discovered the supply hoses were also wet, so a twenty minute job ended up taking a couple of days and became quite expensive! (waiting on parts!)

The old domino situation, don't you just love it!!

Once again, well done!

Enjoy the that satisfaction!

Cheers, qldit.


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## Raylo

*Re: 95 Chevy S-10 4.3L TBI - Idle troubles*

The trick is to get the kids to help with the repairs in hopes of starting them on their way to being self suficient auto techs or at least able to deal with repair shops intelligently. Then dad can rest! I have a friend who is constantly visiting the Crazy Rays wrecking yard here for parts damaged by his new drivers. Last week he got a hatch door a hood and a headlight assembly. Now he needs a pair of aluminum wheels that had a run in with a curb. Bt at least there's nothing to diagnose except for bad driving.

You are right about the fuel pressure being a sneaky thing to diagnose. On the 4.3 CPI engine that runs at much higher FP (something like 50-60 psi) a slightly low FP (by 10 or 15 psi) will get you a no start. I had that one and it had me going (or not going!) for awhile.


[QUOTE= If is was not for keeping your kids in vehicles, what would dads be good for, right? 

Paininthebrain, I too had that problem several years ago with small chevy. Yes, when the fuel pump pumps the fuel right back in the tank it will not make the correct amount of fuel pressure for the TBI system or injectors. Not knowing what is wrong and how to fix it can be a hardship. I have felt your pain.


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