cramez Posted March 11, 2012 Report Share Posted March 11, 2012 (edited) Working on an 02 Monte Carlo SS, 3800 non-supercharged, 170k. Tooling around town, the car seems to run OK. When you step on it to jump on the freeway, goto pass, etc., it will wind up to about 4,000 RPM and "chatter." It won't shift until you take it down to below 3/4 throttle. The exhaust resonator is rotten and leaking, bit I can't see how that would cause this. I can't find any major vacuum leaks, and the fuel pressure is normal, even when revving it up. The only thing I can think of is maybe a partially plugged cat? Any idea how to check that without just cutting it off? Edit: Forgot to add, the check engine light is not on, and there are no codes coming up. Any advice is appreciated, this thing is making me crazy(er) Edited March 11, 2012 by cramez Quote Link to comment Share on other sites More sharing options...
Ramblin Garage Posted March 12, 2012 Report Share Posted March 12, 2012 To check the cat, drive or rev the car up a decent amount, the cat will start to glow red if it's bad, It sounds like it may be a cat Quote Link to comment Share on other sites More sharing options...
cramez Posted March 12, 2012 Author Report Share Posted March 12, 2012 That's one of the difficulties I've been having diagnosing this, the cat isn't glowing at all, and seems to be hotter behind it than it is in front of it. I'm still kind of thinking that's the issue (it's the original one with 170k on it), I just don't have the cash to just throw parts at it and hope one works. Quote Link to comment Share on other sites More sharing options...
AL Posted March 12, 2012 Report Share Posted March 12, 2012 If you are willing to do this test, it will determine if its the cat... Cut your exhaust before the cat... Leave the rest of the system in place and drive it at WOT, if it revs higher and the problem appears to be gone, its the cat... Also, with it being hotter behind the cat than in front, that means there is restriction (that is if behind it you mean towards the rear of the car) Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted March 12, 2012 Report Share Posted March 12, 2012 the catalytic reaction of the cat does cause some heat to be generated. how much, i couldn't say though. Quote Link to comment Share on other sites More sharing options...
AL Posted March 12, 2012 Report Share Posted March 12, 2012 A clogged cat gets really hot though Quote Link to comment Share on other sites More sharing options...
Ramblin Garage Posted March 12, 2012 Report Share Posted March 12, 2012 this is just kind of a shot in the dark but does anyone think that it could be because of the bad resonator not giving the engine enough back pressure? I wouldn't think that's it but it seems like it could be a possibility? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted March 12, 2012 Report Share Posted March 12, 2012 A clogged cat gets really hot though true, anything making significant backpressure will cause excessive heat, but being a higher temp behind the cat alone is not reason enough to suspect it, since it's actually normal. no temp increase means the cat isn't catalyzing the spent air/fuel mixture. that being said, the cat is highly possible. remove an O2 sensor to allow a different place for exhaust to vent? it's gonna sound horrible and you'll be in open loop and will set DTCs, but it might be the least destructive method. Quote Link to comment Share on other sites More sharing options...
AL Posted March 12, 2012 Report Share Posted March 12, 2012 Its possible, yes, but the 02-03 Wbodys had issues with the cats clogging... Breakdowns 03 GPGT and my old 03 GPGT both had clogged cat issues show up in Dayton at the 2010 meet I think... His was worse than mine but once we found his problem, I soon after found mine Quote Link to comment Share on other sites More sharing options...
91LuminaEuro Posted April 11, 2012 Report Share Posted April 11, 2012 Working on an 02 Monte Carlo SS, 3800 non-supercharged, 170k. Tooling around town, the car seems to run OK. When you step on it to jump on the freeway, goto pass, etc., it will wind up to about 4,000 RPM and "chatter." It won't shift until you take it down to below 3/4 throttle. The exhaust resonator is rotten and leaking, bit I can't see how that would cause this. I can't find any major vacuum leaks, and the fuel pressure is normal, even when revving it up. The only thing I can think of is maybe a partially plugged cat? Any idea how to check that without just cutting it off? Edit: Forgot to add, the check engine light is not on, and there are no codes coming up. Any advice is appreciated, this thing is making me crazy(er) Did you ever find the culprit of your problems? I'm interested in knowing what was causing the issue. Quote Link to comment Share on other sites More sharing options...
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