My friend has a 97 Sunfire GT 2.4 auto with 82k miles. The water pump was bad, so I had it towed to my work and I replaced the water pump (PITA, btw). Well, after I got everything back together, it idles very eratically, misses, bucks, etc. It will eventually die if you let it idle too long. Once you start moving and the RPM's go above 1000, it runs perfect. She said that it didn't do this before, but I think she didn't notice it since the lower passenger side motor mount was toast. I did a search, and swapped out the MAP, TPS, and IAC sensors off of my buddys Alero 2.4. Nothing changed. I checked for vacuum leaks and couldn't find any. There are no hissing noises under the hood. There were a few hoses that were pretty cracked, so I repaced those as well. Nothing changed again. I had the codes pulled, even though the engine light isn't on. Nothing came up. Any suggestions?

i think ive heard that you should change the timing chain whenevery you change the waterpump, im not completely sure tho, im just going by WOM.

Hmm, I thought the advantage of the timing chain was that it didn't have to be replaced like a belt. Would not replacing the timing chain cause these problems?

well timing chains DO stretch as metal fatigues.... if you have to remove it, and you are near 100k (86k) might as well do some preventative maintainence... not really needed, but wouldnt hurt.

your timing may be off...

It sounds like the timing might be off.When i changed my cam,the timing was off by 1 tooth,and the car idled pretty rough.


Peter
'06 Cobalt ss/sc W/G85 Package
Gm Stage II W/2.79" Pulley
K&N Drop In Filter
Custom Magnaflow Dual Exhaust