I've had my LS since it was brand new, now it's got 96,000 miles on it and over the last 6-8 months it's began giving me some issues. First, it's got this rattle when running at higher rpm's, such as when you're getting on it while passing someone or taking off quick at a stop light, but it doesn't do it all the time. It goes away soon as you back off the throttle a bit. It also has a bit of a whine or whistle sometimes as well when doing the same thing. Second, when taking off, it still has decent low end, but around the mid range it begins to bog down almost like it hits a wall or dead spot and you have to press down on the throttle a bit more then it's like it loosens up and takes off. On a more recent note, while on the interstate, if you mash down on it to speed up or pass someone, it'll shift down and rev up but not go anywhere, just sit there and roar. It's becoming a bit of a fight to keep it at 70mph or go any faster, and the car used to be able to run 60-90mph in just a few seconds.
It's got a new air filter, new pcv valve, oil changed regularly, the usual routine maintenance. Any ideas as to what might be causing my issues? I'm going to disassemble the MAF sensor today and clean it, but what about any other valves, sensors, or even the cat?

 

I heard rumor GM had a recell on cats in certain years of our cars, and as a result extended warranty on that. First, I would do some Google searches or call your dealer, see if you Monte fits into that recall/extended warranty. If so, get that done first, as it will probably be the issue (and could be fixed on GM's dime).

Without hearing it, it's somewhat tough to be exact. I have a '94 Grand Am with a 3100, I noticed a tick noise once (no other symptoms) and the noise was a loose spark plug (long story but the plug hole in the head stripped out, fixed with a heli-coil). Might want to lightly wiggle the plugs when the car is cool and check for that (doubt it's the issue, but I only noticed the ticking when revving the car).

As for the shifting and revving, check your transmission fluid! I'd do that ASAP. I know certain years GM decided not to put a Trans Dip Stick on the car (I think is completely silly). Luckily, I have not had to deal with that, so check around and see if someone has a published way to check the trans fluid.
Now, again, a plugged cat could very well play into your shifting problem. But still, does not hurt just to make sure you have trans fluid (and you're not leaking it).

Hope this is a start.

 

I just pulled the MAF sensor and cleaned it, while I was under the hood, I checked all the vacuum lines I could find as well as the trans fluid. There was plenty of trans fluid but it was looking a little dark, so I'll probably get it serviced soon, I was going to service it soon anyways. I'm getting conflicting reports on the recall, meaning that there was indeed a recall on the cats for the 2002 Monte Carlo, but one dealership rep online said it was covered for 10 years or 120,000 miles...but when I called a local dealership to get everything set up to take the car in, they said it was only for 8 years/80,000 miles. I'm going to call around to some other dealers tomorrow morning to see what I can find out. It'd be nice if it were replaced for free but I've found cats through autozone for $75, and for another $25 or so, I can get it welded up a a local shop. I figure it probably needs one anyways since it's getting near the 100,000 mile mark. I think that may be whats rattling when I stomp on it sometimes. It's not a ticking noise, more of a shaking marbles in a metal can kind of noise.

 

I had a plugged cat on my 2002 Didn't have any power over 35-40mph. I
Had 90,000 on it. I live in california and dealer said it was covered 100,000 8yrs. In cali it was a $1300 fix under warranty. good luck

 

I would imagine GM has a technical service bulletin on this. Using this site http://sm.gpona.com:9001/si/home.do I think i found what you need, I can't attach the PDF I made because it exceeds the MCF file limit. This is good for 10 years up to 120K miles. Take the info I am providing here to the dealer, it should have everything they need to cross reference this. It also explains why the cat fails (insulation inside it breaks up).

Here's all the ID stuff I have on it:
Document ID: 1703629
#05551: Special Policy Adjustment - Catalytic Converter - (Sep 14, 2005)
Hopefully this link can take you directly to the article to print:
http://sm.gpona.com:9001/si/showDoc....703629&from=bs

Here's what it says to the letter:

regardless of ownership. The repairs will be made at no charge to the customer.

BTW - Mileage is not everything to the Cat. I have a '94 Grand Am with a 3100 and over 200K miles, it still have the factory cat (but not the factory muffler).

Start with the Cat, this is a known issue for your car and a free fix from GM.

 

I found that Special Policy Adjustment #05551 and my Monte Carlo fits in with all the criteria, so I contacted a local dealer and made an appointment to bring it in and have them look at it. They can run a test on it to see if it's going bad and if it is, they will replace it for free. If if isn't, at least the test is paid for since it was part of a recall and we can rule that out.

 

Took it to the dealer today, they didn't want to fool with it at first because the check engine light never came on, so they assumed it was fine. I insisted they test it, so they hooked up a computer to pull any codes and I'll be damned if four codes didn't show up, one of them being the cat. They also noticed it rattling when they revved the car up, so the service manager said they would take care of it and the policy covered it so I have zero out of pocket costs. I have to wait for a new cat to get here in the morning, then I just have to drop the car off and have them switch it out. The three other codes that popped up were for the thermostat, egr valve, and oil pressure switch. I can take care of all of those myself though. It definitely pays to do your research!

 

That's great news. I wonder if the cat may have caused the EGR code? May want to wait on the EGR issue, but the T-Stat and oil pressure switch, I'd nail those out.

Good job insisting they check it out. I hate when I hear stories of mechanics/dealers having to be pushed a little extra to check some of these things out. But so long as they did not make a big fuss out of it, at least you got them to do it.

 

That's kind of what I'm wondering, although it probably wouldn't hurt to clean it. Another thing I've thought is that if it is dirty or bad, the bad cat may have been what caused it. Anyhow, the service manager told me how to take it off and clean it with a little carb cleaner. Just curious though, how do you go about getting the EGR tube loose from the bottom? It looks like a tight fit to me.

I was a bit annoyed with them at first because he was so reluctant to test it, but he changed his tune pretty quick when those codes popped up on their computer as well as hearing the rattling that the cat was making when they started the car and revved it a bit. Still confused why it didn't throw the check engine light on though.

 

The Maniac is right, there is a Special Policy on some '01-02 models. You can check your vin # most likely at the link he gave you. I had mine replaced at no cost, only "symptom" mine had was the CEL came on - after having the cat fixed, we realized it had been down on power a bit, was much peppier afterwards. I didn't fool with the dealership as they already acted like they didn't know anything about it. I called GM direct and they set it up with the dealership.