# 2000 Chevy Cavalier- Running Lean and shakes on idle



## jon23781 (May 17, 2011)

I am sorry if this is a repeat post, I tried searching for it and didn't seem to come across the same issues.

I have a 2.4L 2000 Chevy Cavalier Z24 that started to shake on idle. I have replaced the MAP Sensor, Idle Air Control Valve, the upstream and downstream Oxygen Sensors, Spark Plugs (twice), and even the Coil pack housing (not the coil packs themselves).

Anyone have any ideas?


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## Wrench97 (May 10, 2008)

If it's throwing lean codes, I'd be looking for a vacuum leak.


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## jon23781 (May 17, 2011)

wrench97 said:


> If it's throwing lean codes, I'd be looking for a vacuum leak.


I tried looking for leaks and I couldn't find anything. I'll look again, maybe I missed something. Thanks for your help.

Oh and I forgot to mention that one of the symptoms is when I press the clutch the engine will rev up to nearly 4500 rpm. 

I just replaced my coolant temp sensor, still no change. I'll look for leaks again tonight.


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## Midnight Tech (Dec 31, 2001)

Get a can of carb cleaner and spray anywhere you might suspect a leak - listen for the speed of the motor to change.


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## dkan33 (Sep 26, 2010)

Try pinching off vacumn hoses one at a time


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## whatup (May 22, 2011)

it is sucking air somewhere. take wd40 and spray around vac hoses and intake where it speeds up at is your prob


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## jon23781 (May 17, 2011)

Last night I finally had decent enough weather to check for leaks and I sprayed every part of the intake with Throttle body cleaner and the car had no reaction... Is there anything else I could be missing, maybe Fuel Injection issue, fuel pump regulator, fuel filter?

I have been asking around and no one has ever ran into this issue without it being a vacuum leak, as you guys suggested. Is it possible the my recently changed O2 sensor could have gone bad again and could be causing an incorrect fuel to air ratio?


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## Wrench97 (May 10, 2008)

Is the check engine light on?
Do the power brakes(vacuum assist) work correctly?


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## jon23781 (May 17, 2011)

wrench97 said:


> Is the check engine light on?
> Do the power brakes(vacuum assist) work correctly?


The check engine light is on. It was reading bad O2 and miss-fire 3 weeks ago. I replaced the down flow O2 (since I replaced the up flow O2 6 months ago) and the spark plugs and had the codes cleared. 

The check engine light came back on a day after I posted this issue. I ordered a OBD2 blue tooth adapter which I am going to connect to my android phone to read the codes again, I haven't had time to run to Autozone or a mechanic (too far away from me) to have them read the codes. I have avoided putting any miles on this car that I don't have to since it is my only vehicle.

Power brakes are working properly.

I am hoping to receive my OBD2 any day now, once I get it I will check the codes again. I was thinking it might be a faulty up flow O2 sensor I replaced 6 months ago, it was duralast brand.


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## Wrench97 (May 10, 2008)

Possible the codes will tell you which O2 sensor(if it is a o2 code), you should also be able to see the real time readings to see how it reacts at different rpm's if the reading if going lean to rich on acc/decel the sensor is working and it's running too lean.


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## jon23781 (May 17, 2011)

Hey everyone. I appreciate all the help! I found out the hard way that the issue was the Timing Chain. I had it replaced 6 months ago and the tensioner wasn't set correctly so when the car would idle the timing chain would loosen and cause the car to shake on acceleration the chain would tighten which is why I didn't have any issue on higher RPM's. 

My car wouldn't start the Sunday before memorial day (the timing chain broke) and then when the towing company came to pick me up they started it which ended up causing the pistons to hit the valves and broke everything. $3,000 parts and labor to repair. I am either going to buy a scrap engine and rebuild or junk it since the car isn't even worth $2,000. Oh and the mechanic who replaced my timing chain sold his business so I can't ping him for the damages.

So again, I appreciate everyone trying to help, wish it was as simple as an vacuum leak because that is what made the most sense to me as well . Anyway I hope that this post will help anyone in the future who might run into the same symptoms as me. Take care everyone.


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## Wrench97 (May 10, 2008)

It would appear the same because being out of valve timing would create low vacuum, not drawing enough air into the cylinder, it should have had a noise in the front cover on acceleration to go along with it.

Best to look for a used engine that runs well and just swap them.


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## jon23781 (May 17, 2011)

Yeah I didn't think about the valve timing creating a low vacuum. But it didn't create any noise what-so-ever, which is why I focused on the air intake leading into the intake manifold. Never would have guessed timing chain, but it is a good lesson learned.

Yeah I am pretty certain I will look for a used engine to swap, until then I will asses whether I will use the car or look to sell once running. If I decide to keep it then I may buy some performance parts to sub-in to the new used engine. We'll see.



wrench97 said:


> It would appear the same because being out of valve timing would create low vacuum, not drawing enough air into the cylinder, it should have had a noise in the front cover on acceleration to go along with it.
> 
> Best to look for a used engine that runs well and just swap them.


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## Midnight Tech (Dec 31, 2001)

jon23781 said:


> the towing company came to pick me up they started it which ended up causing the pistons to hit the valves and broke everything.


If they tried starting the car it seems the towing company might be liable for the damages....


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