Hi, I just got my hands on a 2002 monte carlo ss. Ol earnhardt edition. I bought it about a week ago. Real clean interior, exterior. Looked like a brand new car. Only 61k miles. I absolutely fell in love with the car. Was driving it for about a week when it started having an issue. It idles fine, starts up perfectly, shifts great. The only problem is that at 2000 rpms, it hesitates and rides rough. It'll power through that and it smooths out at 3000 rpm's and then it won't rev past 3500 rpms. No check engine light or anything. Since this problem started, I have done an oil change, coolant flush, replaced the thermostat, replaced the transmission filter and fluid, replaced the fuel filter, and replaced the EGR valve. I went and had it checked for codes and only one popped up for the EGR valve. After it was replaced, no code but problem still persists. I smoked it to check for vacuum leaks and found nothing. I am genuinely stumped on where to look next. Was wondering if anyone here has had a similar issue or could maybe point me in the right direction as to where to look.

 

Could be one of the sensors on the throttle body. I would check the MAF first. Unplug it, drive it and see if the issue is still there.

 

I'll try it but wouldn't it just not run with the MAF out?

 

So after messing with it for a bit, I've discovered some new info about symptoms. It revs fine in neutral. So it won't put power to the ground, shudders at those RPM's and the issue is intermittent.

 

That is an unusual thing.
oil change, coolant flush, replaced the thermostat not gonna fix that issue!?
What about the Air Filter you never said anything about that or maybe some kind of Vermin crawled up into there and left a nest. Exhaust flow is important also so if there is a nest in the exhaust pipe it could be an issue. I doubt the Cat has gone bad but who knows anymore.
So maybe it could be the Fuel Pressure Regulator with that low of miles it might not have been replaced yet.
I found this link that you might want to check out. check it before you get an explosion.
2001 Monte Carlo intake explosion - Engine Troubleshooting
In the event you have no success in fixing this you can give it to me and I will get it fixed. LOL

 

I replaced the air filter when I first got it. Forgot to mention it. Exhaust seems to be flowing fine as far as I'm tracking. I'll give the link a look and see what I find. Thank you

 

Sounds like the problem I had with my monte and a ford truck I had. Both were the CAT converter. On the truck we dropped the exhaust prior to the cat and straight pipe tested it. The truck had not been driven much when I got it. Now the Monte I was driving 100 miles every day to and from work, and it just started acting up coming home. I did not have time to work on it then, so I took it to the dealer and they fixed it with a new CAT. Maybe you can drop the exhaust and put a straight pipe on it to test. My Monte is the 3.4 engine, so I am not sure how yours is plumbed. Expensive if it is the CAT.

 

It's funny that you mention that because that's the conclusion I came to over the weekend. After messing with it and just throwing more stuff at it to try and troubleshoot, my thoughts were exhaust. ZZPerformance sells a high flow cat for about 200 bucks from what I've been seeing online so I may pick one of those up after I get it backpressure tested. Unfortunately the cat is welded all the way up to the rear exhaust manifold so unbolting that to test was an absolute pain. Definitely getting that fixed soon because I have heard plenty of horror stories