99 Grand Am missing at idle

chuckgibson0

New member
Joined
Jun 29, 2013
Messages
8
Reaction score
0
Points
0
I am dealing with an idle problem. (2.4, four cyl.) Four months ago we replaced the water pump, timing chain, guides and tensioner, had the head rebuilt and it has ran great ever since. Now it has started shaking at idle, worse when it is in gear and it seems run a little smoother when it is still cold. I pulled the plugs and they are all burning fine. Pulled the vac line off of the fuel pressure regulator while idling and it made no difference. Pulled and cleaned the IAC valve....no help. Changed the throttle control valve, again, no help. With no good place to get a vacuum reading, I took what I could get and it showed a steady 14#....I don't trust that reading because of the location. There is no valve to check the fuel pressure from but I don't believe that is a problem because during normal or high speed driving, it runs smooth. There seems to be a slight rattle in the area of the timing chain while it is sitting and idling....I fear it may have jumped a tooth on the exhaust cam sprocket though I don't know how to test that without tearing it down to "look at it"....I want to avoid that if possible. I replaced the cat thinking that if it was clogged it might be causing back pressure affecting both the vacuum and the idle. It seemed to smooth it a hair but not much. Do any of you people have any ideas to throw my way? I would really appreciate any help or suggestions you could offer. thank You!
 
have you done a compression test? do you have a check engine light on?
 
have you done a compression test? do you have a check engine light on?

No, I have not done a compression test. If I did one, what would I be looking for? I was trying to figure out how it would test out if the timing chain had jumped a tooth. It runs so well driving it that I figured it had most likely not jumped time. Running the test would not be a problem.

At first when the problem began it threw code PO172. I have not been able to find a vacuum leak. The code was cleared and has not come back. At some point it threw a PO122. Replaced the TPS and the light went out and has not returned... Still idling like crap...
 
Diagnosed- Jumped time

It definitely jumped time. I will start another post to find out what is the best timing chain etc...
Thanks for your input!
______________________________
 
Back
Top