# 1990 Chevy C1500(5.7/350tbi) running rich



## Apocalypse2010 (Nov 3, 2010)

I have a 1990 Chevy C1500(5.7/350tbi), I just bought it from a used car lot and noticed it was running rich(overwhelming gass smell from exhaust). I slid under it to check the connections to the O2 Sen. and found out that the person they got it from changed the exhaust. The new exhaust does not have O2 Sen. or converters. It runs through gass a little fast for my liking. I gave it a full tune up, checked fuses and did pretty much all the things the former owner should have been doing all along. It runs rich , and when on the highway at 65-70 it sputters and you have to give it more gass to get it to smooth out.


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## kjms1 (Jun 4, 2010)

you can add a O2 sensor,, a muffler shop can do that for you, can you see the plug end for the O2 sensor
you need to see if any codes are in the computer ... plus does the service engine light come on when you just turn the key to the run position 

most states now for emission inspection you have to have the converters to pass,, might want to check the laws in your state


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## wolfen1086 (Oct 4, 2007)

if the previous owner took out the O2 sensor is the light on the dash on? If its not check to make sure the bulb is there cause your throwing an O2 sensor code for one. I'd have an O2 sensor installed asap and the computer checked for proper operation too. if the emissions computer is ok start checking to find out what else the previous owned changed thats totally wrong.

Oh btw I heard that in most states modifying the emissions system in anyway is illegal


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## Apocalypse2010 (Nov 3, 2010)

ok so I figured out that I'm completely blind. There is an 02sen. on it but its only on one side and it wasn't the side I was looking at(since I'm use to working on mustangs which have 2 02sen.) I have a new 02sen but the guy cut the connector off and hard wired the current one. It has developed an over heating problem. The water pump is flowing(seen through the radiator), I just put in a new thermostat and gasket, bought a new radiator cap(incase the old one was bad), and flushed the oil system to clear out any sludge that might be clogging the passages. Still over heating and don't know why. I have found out since my last post that there is more things wrong with this truck then I thought, and am now saying f**k it and rebuilding the motor and getting a new trans (since the fool who use to own it either beat this truck non-stop, or never changed the oil since the truck was new). I plan to buy a new wire harrness and computer after rebuilding the motor just to make sure everything is right. I will post back when its done to let you all know if I still need help(as nothing would suprize me at this point).


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## wolfen1086 (Oct 4, 2007)

Ok so you learned that theres only one O2 sensor, that doesn't make you blind it makes you a little smarter than you were before, just be glad its not a S-10 Blazer the one and only O2 on mine was between the trans bell housing and the body, try changing that one with man size hands. Now on to your over heat problem, first is it boiling? if its not go but a candy thermometer, open the cap, ( cold) make sure the rad is topped off, and start it when the thermostat opens and the coolant is all warmed up it should read somewhere around 195, a degree or two off each way is no biggie, while your at it check the fan clutch, thats different from Fords too. Also check the temp sensor, Chevy's are famous for those going bad, and a bad temp sensor will make your life hell


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## Apocalypse2010 (Nov 3, 2010)

yea Temp sensor was the first thing I changed i just for got to put it in the post. I do know some chevy stuff but I'm use to working on older chevys like 60's and 70's. All this fuel injection stuff makes motors act like theres one thing wrong when it could be 7 small other things working together to cause the problem. I think the hardest o2 sensor I had to change was on a import car...... I think it was an Eclipse..... pain in the *** when you have man sized hands too (I'm 5'11 and 300 lbs so I know all about trying to squeeze huge hands into tight spots on cars). S10 blazers are easy to work on if you've change out the motor to a V8.


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## wolfen1086 (Oct 4, 2007)

Always remember one thing thats VERY important about your Chevy, you can yank the TBI and slap a Holly right on it, it fits.
My point isn't that you can or should, my point is that Chevy changed very little from the 60's and 70's till now, the engine is the same, just more junk on it now. same trouble shooting on the mechanical parts  And think of a TBI as a Rotenchester with a big hole in it ( makes it a lot easier to work on a TBI)


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## Apocalypse2010 (Nov 3, 2010)

ya know I never looked at it that way. A holley will fit right on the intake for the TBI? I didnt think it would bolt up, I thought I would have to get a new intake to carb it.


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## wolfen1086 (Oct 4, 2007)

Nope, I had a 4.3 in my S-10 blazer the TBI crapped out with a crack in the lower body, so I put a rotenchester on it until I could rebuild the TBI. But in reality all the TBI is , is a carb with no choke plate, and instead of a needle and seat theres a really big jet set shooting gas in


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## Apocalypse2010 (Nov 3, 2010)

maybe I'll just get me a carb and be done with that part. As for the over heating its building good pressure. Originaly there was no oil getting to the top of the motor(or very little) but after the flush it started pumping to the top. The oil pressure started jumping up a little higher then it had previously been. It usualy sits at about 35, but now it jumps up to about 45 and every once in a while it drops back to 30 and then bounces back and forth between 30 and 45. I'm pretty sure the oil pump is shot or going so I plan to get a high vol pump and change it.


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## wolfen1086 (Oct 4, 2007)

Before you do anything like there keep in mind the legal aspect of doing that, in most states its illegal to remove or disable ANY part of a 3emmisions system, that and the fact you can get ANY part for your Chevy online and a TBI unit is (1) easier to rebuild (2) cheaper than a good carb, (3) more reliable than a Rochester or Holley. (4) will keep ya out of jail.


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## Apocalypse2010 (Nov 3, 2010)

I live in Kentucky....lol. They don't care about emmisions here. The law here says as long as it has exhaust, lights and its plated and insured its ok for the road. We don't have emissions testing here yet(key word yet). There is a guy around here that has the same truck as me and he took the whole computer system out and dropped a big block in it and dual 3inch exhaust with no cats, no o2's, and just flowmaster race mufflers. But then again this place is very open about most of the laws. The law for height limit for a lifted 4x4 is " Keep it within morals". there are trucks around here that you could park another car under and they're legal.


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## wolfen1086 (Oct 4, 2007)

I did a little checking I might have been incorrect about the manifold, some you can do it some you can't, might want to verify what I said with a mechanic in a shop just in case.
I still think ya need to drill a hole or two and put in a O2 sensor first though, TBI is way more reliable than a carp, the injectors hardly ever go bad or even get gummed up, and a TBI only has one moving part


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## Apocalypse2010 (Nov 3, 2010)

well it has an 02, I found that. I just have to change it and the guy hard wired it to the harness instead of getting the one with the plug on it. As for the TBI, if I can get it to run properly without spending a ton of money I'll stick with it but I have a feeling I'm going to end up dumping a ton of money into fixing it. I got this truck for cheap and now I'm finding out why.


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## Basementgeek (Feb 7, 2005)

I would stay with TBI if all possible, just my 2¢

As wolfen said it will be more reliable than a "carp" :laugh:

BG


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## Apocalypse2010 (Nov 3, 2010)

unless I find a TPI from a camaro or somthing then I might change it up a little. I mean I want to stay with fuel injection if I can but if swapping it out for a carb is going to be a better option then thats what I'll do. I'll have to do some price checking on some stuff.


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## wolfen1086 (Oct 4, 2007)

Have you tried Rock auto? they have just about every part for almost all cars and trucks.
and a TBI rebuild kit is real cheap too Ebay has em for $25, and reading a check engine light if its OBD1 requires a paperclip.


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## Apocalypse2010 (Nov 3, 2010)

Check engine light hasn't come on, except when I turn the key before starting it. Then it goes off when the motor fires up. I will look into Rock auto though. I'm thinking that I'm going to try to find a TPI though... because I want it to have a little git up and go because I'm a certified storm spotter and plan to be on a team here. I dont want to be tryin to get out of the way of a storm and not have the power I need....lol


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## wolfen1086 (Oct 4, 2007)

certified storm spotter? yea then you want to keep the TBI no matter what, I've seen enough on tv to know you guys need all the get up and go you can get, and a TBI IS a hellofa lot faster responding than a carb


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## Apocalypse2010 (Nov 3, 2010)

yea TBI is faster to respond but I can fine tune a carb to get better horse power then I can a TBI.... but a TPI system would give me a few extra horse right off the bat if I swap out the heads with it. the original plan was to rebuild the motor and put a comp cams Mutha thumpa cam in it, get it bored 30 over and get a stroker crank and make a 383 but keep it injected. If I do that it would be hard for me to fine tune the fuel ratio to take advantage of the bore and stroke(unless I change out the injectors for bigger ones). I found someone who wanted to trade a 454(with a carb) for my 350(with fuel injection) but I haven't decided if I want to do that. It will give me extra horse and torque but its going to eat up extra gas in the process.


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## wolfen1086 (Oct 4, 2007)

454 is a gas hog, but you'd be unstopable
I'd love a 454 but I wouldn't be able to afford gas for it LOL


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## Apocalypse2010 (Nov 3, 2010)

I found a forum about big blocks and a guy on there said he had a chevelle with a 454, 700r4 trans, and 4:10 gears, and 31 inch tall tires and he could do John force burn outs all day in 1st and 2nd..... but got 20 -25 mpg on the highway.


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## wolfen1086 (Oct 4, 2007)

WOW, in that case I'd have to take it a 454 that burns out is normal but one that even gets close to 25 is a rare find.


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## Apocalypse2010 (Nov 3, 2010)

thats what I'm saying. I don't know if I should believe it or not. I've seen plenty of 454s but none that get good mpg. I already have a 700r4 and I can get 4:10 gears for my truck for some what cheap, and I'm runnin 31 inch tires as it is so I should get right around the same mpg.


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## Basementgeek (Feb 7, 2005)

Guys like to lie about MPG. 
7.4 L in a 1900 C1500 is rated by EPA 9 City, 10 road.

BG


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## wolfen1086 (Oct 4, 2007)

Not me, I'll be honest car, 05 Malibu aluminum 3.1. 22 mpg city
Jeep 01, 2.5 12 on a good day 14


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## Apocalypse2010 (Nov 3, 2010)

lol well I got my 90 chevy truck with a 350 and it runs right around 3mpg I think. I really don't know how much it actually gets but it seems like its not any more then 10mpg. I drove it home from the lot I bought it from which was about 65 miles from me and it used up a half a tank of gas.


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## wolfen1086 (Oct 4, 2007)

3? DUDE, there is either something wrong or your pulling a hellofa load, or you have granny hears in the diff, I had a 76 C10 witha 350 and the least I ever got was 8, max was only 12


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## Apocalypse2010 (Nov 3, 2010)

lol I was being sarcastic about the 3....... but I dont think it gets any more then 10. I mean like I said I went about 65 minles and went through a half a tank of gas doin 65-70mph.


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## Basementgeek (Feb 7, 2005)

Check out Jegs for carbs:

http://www.jegs.com/c/Fuel-Carbs-Intakes_Carburetors/10271/10002/-1

BG


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## wolfen1086 (Oct 4, 2007)

Oh yea I wish I could put one of those on my wifes Malibu


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