Very sluggish acceleration

**Nchristopherson** · 11-09-2014

My car has been having some interesting issues lately where it just does not want to make power. The car won't go over 3.5k RPMs ever, and if I put too much throttle in, it won't shift into the next gear and will start to actually decelerate. If I slowly stay in the gas, I can get up to speed, it just takes an incredibly long time.

**Scottydoggs** · 11-09-2014

sounds like a clogged cat.

year make miles, last known tune up? the check engine light on? does it flash when you floor it?

**Nchristopherson** · 11-09-2014

Thank you! That's what I thought, I tried to free the downpipe to resonator bolts but just can't get good torque on them under the car so I am taking it to the guy I bought the car from. He's offering to fix it for free but he seems to think it isn't the cat. As he said, "It sounds like the car has flow", which I disagree.

2002 Grand Prix GT, Last tune up about 3 months ago. SES is on, but doesn't flash when I floor it.

To complement why I think it's the cat, the exhaust flow out the tailpipes is so low I can cover both with my hands and feel almost nothing. There are no exhaust leaks. Also, the engine runs hotter than normal.

**Scottydoggs** · 11-09-2014

have you had the car scanned yet for the code? the code always leads you to the problem.

**Nchristopherson** · 11-09-2014

Yeah I'll go scan it real quick, it's just a PITA cause my friend has my ELM327 so I gotta do it in HP Tuners. iirc, one is the TCC circuit in the transmission, and the others were the EGR not functioning correctly, but I replaced it with the one from my other car.

**Scottydoggs** · 11-09-2014

those wont make the car do this.

does it sound like a vacuum with a full bag when floored? like it just cant suck any more air? even tho it should? if so thats a clogged cat for sure.

you can also take the up stream o2 out, this will make a large exhaust leak, if it runs better the cat is clogged up, cause the leak is pre cat.

**Nchristopherson** · 11-09-2014

Ok, just scanned, the codes were a matured misfire (had 4 and 6 reversed when I changed plugs) and EGR circuit. It definitely has that sound like a vacuum. I'll go try the O2 sensor.

On a side note, when I got the car, the guy I bought it from had put ACDelco iridiums in there and I didn't know if they were old or not, so I switched them out with Autolite 106's. In this whole process, one of the things he told me to switch was the spark plugs back to the original ones. It seems like the car runs worse now, during acceleration it kinda stutters a bit. Also, if I rev the engine way up and let go, it stumbles and almost kills.

**GT in Kennesaw** · 11-09-2014

Originally Posted by Nchristopherson

My car has been having some interesting issues lately where it just does not want to make power. The car won't go over 3.5k RPMs ever, and if I put too much throttle in, it won't shift into the next gear and will start to actually decelerate. If I slowly stay in the gas, I can get up to speed, it just takes an incredibly long time.

I've had those exact symptoms on my 01. Twice. Both times the dealer replaced the cat (warranty). Both times it fixed it. There are 2 causes for the cat clogging. 1) there is some ceramic parts where the exhaust enters the cat which break up and literally block the exhaust flow. 2) is worse. metal from the pistons, cylinders and rings wears off and eventually causes the same symptoms. I'm only familiar with #1, and do not have any verification of #2, just was told that by the dealer.