2002 Grand AM GT Acceleration problems ...???

[mwd83]

Hello, all. I have a 2002 Grand AM GT 3.4L V6, 89k miles and well taken care of. I had new plugs & wires put in less than a year ago as well as a transmission fluid change. I've also added Lucas Transmission fix recently, as I thought this might have been a transmission problem. That didn't help, and the more I read I'm finding out it might be something else. So I'm collecting opinions.

It starts fine and runs fairly well until you try to accelerate up, such as driving on an open road or accelerating to merge onto a highway. It seems very hesitant and seems to lose power. The farther I push the pedal, the RPMs jump way up, almost like it's riding in a lower gear and there's hardly any acceleration. I have a cold air intake and have had one for several years. The engine seems to be sucking in an abnormal amount of air during this acceleration problem. I also seem to be using double the amount of fuel than normal, as I've had to fill up twice this week and that's not normal for the miles I drive.

I've read things from PCMs, to fuel pumps, air flow sensors, etc. Is there anyone that knows anything about this problem? If there's anyway I can narrow it down, we have a very good family mechanic, trusted for over 15 years. I just need something to tell him as I'm getting no error codes when I test it myself and no warning lights. Any posts would be appreciated much. Thanks!

Matt

[3100]

- plugged cat converter or muffler
- bad 3rd clutch
- or bad TFP switch (transmission fluid pressure switch)

[grfnkl]

I would also say Cat converter as the #1 culprit to your problem.

[mwd83]

Thanks guys, if you check this .. Cat Converter was clogged completely .. you guys nailed it and helped my mechanic find the problem a lot faster. Thanks again.

[3100]

glad to hear that, please post back your mpg increase with new cat.

[mwd83]

Not a super big difference on the MPG, much better than when it was clogged obviously. Hard to notice with the gas prices goin up again, lol. Definitely sounds a lot deeper and more powerful like when I first bought it. It's got a ton of HP back into it and fun to drive again.

[3100]

thx for the update...

[shark7000]

This happened to me to. We had a Mustang that someone totaled, while it was parked on the street. I used one of the high flow cat's off that. I had to cut and weld it all my self, but it seems to have more power than when I bought the car. I replaced the stock resonator, since two bolts broke off, with a cherry bomb that I had sitting around the garage. It sounds better. It looked like metal flakes plugged up my cat. I think it's from the piston slap that this car has had since I got it with only 23,000 miles on it. This is a good reason to let the engine warm up before driving. After drive with no power for over six months, now I find myself going too fast with little acceleration. What I don't get is that the computer could not give me a code to figure out this problem a long time ago.

[3100]

one of the first signs that your cat or muffler is really blocked is that your car is not coasting nearly as easy as it used to. Feels like something is holding you back like dragging brakes etc... and significant drop in mpg

I was able to average 265 miles city/highway + racing a lot when I was younger on a 15.2 gallon tank from F to the low fuel lamp on. (that is about 13 gallons considering that 2 gallons are left when light comes on. When my cat was blocked mpg dropped to 210 so about 3.5 mpg decrease.