My 2002 SS seems to be in limp mode. Sluggish off the line strange whistling noise but not sure exactly where it’s coming from. Will shift at higher speeds. No check engine light and my diagnostic reader pulled a p0104 code (replaced the mass air flow sensor) but problems persist. No codes now. Checked for vaccuum leaks and that search came up empty. I’ve seen some stuff about solenoids in the transmission but hoping for some definitive info before diving deeper.

 

This is reminding me of the stuff I am dealing with on my daily driver, a 2004 Grand Am. In my case, I am starting to suspect a blockage in the exhaust.
Do you have ability to read data from the PCM? Such as MAF, Upstream O2, KR, fuel trims, to name a few. In my situation, I am noticing cold start, car runs great. After it warms up, my fuel trims begin to report very lean numbers and if you just tap the gas, the KR can be a couple degrees or spike to 16 degrees. As KR increases, the car retards timing and that reduces performance. Such as, my Grand Am cannot keep up very well at 60mph in its current state.
I also found at the start of this issue 3 of 6 plugs had a very wide gap, I suspect this is a sign of the issue. Too much heat possibly backing into the heads.

Side note, I recently spoke with a friend about my problem, he mentioned a clogged cat sometimes makes a sound like a Hoover vacuum. I found this video of a guy working on a 3400 Impala, and he had a whistle with his issue (at least I assumed it was a related whistle).

I have my own back pressure gauge on order and hope to test my Grand Am soon.

 

If your Catalytic Converter is clogged it will rob all the power from the car, I had the same symptoms on a 4th Gen MC I owned and I used to travel with it for my job around a 100k on it when it did that and the shop I always took it to knew exactly what it was. put on a new Cat and WALA.

 

I had a shop look at it…clogged catalytic converter. Way too expensive to replace it the conventional way. I’m in the emissions **** state of CO so going aftermarket is difficult since the websites won’t ship here. Thanks for your help!!

 

At least the problem is now figured out. In my case, it does not appear to be an exhaust blockage based on a few tests I have done. My journey continues.
Hope you can find a cost efficient solution.

 

If it’s not an exhaust blockage what are you leaning towards? I had a 1997 Grand Am GT (loved it!!) that had a lot of fuel system issues (HEET seemed to work every time). At one point the car wouldn’t start at all and that was a result of the fuel filter failing. Your issue sounds a lot more complex than simply adding HEET obviously. Learning from your experience with this could help me in the future…

 

I have owned a lot of Grand Ams, great daily drivers. I had a 1993, 1994, 2002 and the current 2004 (this does not count the 1999 I bought and flipped). I miss the 1994 and sad to see the rust issues of the current 2004.
Any case, I can run you down the quick points of what I have done to lead me to where I am going:

1. - Initial problem, I checked spark plugs and found a large gap on 3 of 6. I just opted to replace them. Did not fix the issue.
2. - Since the two big issues seen on my Scangauge II that I have in the car was running lean and detecting knock, I did a fuel pressure test, perhaps the car is not getting enough fuel. That passed. I even did an injector balance test, all are performing properly.
3. - Thought it was an exhaust blockage. Bought a back pressure tester. Passed. Shop book claims I need 2psi of back pressure to be considered an issue, I got .5 and MAYBE a peak/blip of 1.
4. - Removed the upstream 02 sensor from the car, leaving a huge exhaust leak and zero help from the 02 sensor for fueling. Warned to car up, took a ride around the block, still crazy knock. 2nd confirmation that it is NOT an exhaust blockage (as the exhaust clearly had a second exit). And heavily suggested NOT the 02 as the computer would be compensating for the lack of 02 and the knock behavior pattern should have changed.
5. - Re-installed the O2, disconnected the MAF. On the 3400, this sucks as the car then maxes transmission line pressure making for some very harsh shifts. But, again, warm up, ride around the block, no change. Still knock.

This is really limiting my options. I have three noticeable things, the Knock, very lean fuel trims and why did the gap on spark plugs with 15k widen (my assumption was either a manufacture problem or extremely high heat around those cylinders). Every thing I can logically think of is checking out. I have consulted with a few friends that are very knowledgeable on these cars for a variety of additional ideas. One made a suggestion I started leaning on. Disconnect the knock sensor, with no ability to detect knock, do my fuel trims look normal? I took it for a ride and it performed normal and fuel trims looked normal (shy of a couple very rich blips, but that was very few blips). This is suggesting a potentially bad knock sensor. I have one on order and shall see if that is the true issue. I have never heard of a knock sensor on the 3400 or 3800 failing, so I really had trouble believing this is the issue. See what happens soon.

 

Well well well, a fellow 02 Monte guy, cool. A bit of a pickle, nothing that can't be overcome. Left you a visitor message on your forum page. Cat cleaners etc, will get you through this.