medicmandan

Just started about three weeks ago. Is ok when the engine is cold. When it starts to heat up there is no power. Idles just fine. If you step on the gas it hesitates before finally picking up speed. It has no power on hills or anything. Even with the pedal to the floor it goes slow up hills.

No check engine lights. My dad's mechanic had it for three days and couldn't figure it out. He installed new plugs and wires. He checked the catalytic converted and tested the fuel pump.

There hasn't been any work to the car in a while. About two months ago I replaced the coolant temperature sensor.

Any thoughts? I'm dropping it off to the dealer later this week.

truck150

my 02 had the same problem where it had no power and could barely pull its self around then i found out that the cat convertor was plugged i replaced that and then it was fine. before you change it try taking the bolts off the collector so the exaust is coming straight out the exaust manifold and take it for a quick drive. make sure you tie up the rest of the exhaust. if it has its power back than you will know that you need to change the cat. the process takes about 30min hope this helps

richtazz

How did your father check the converter? If your converter proves to be bad (you have the classic symptoms of one), GM issued an extended warranty on 01-02 Grand Prix's for a known issue that covers replacement for 7years or 120k miles.. There is a write-up about it in the tips and maintenance sub forum at the top of the GP forum, check that out.

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medicmandan

I have no idea how the mechanic checked it, he just said he did.

That issue doesn't cover my engine. I have the 3100.

BNaylor

There are different ways to check for a clogged CAT convertor but my favorite DIY test is using a standard automotive vacuum gauge. Here is a old thread for review applicable to CAT testing on a Grand Prix equipped with a 3100 engine. Best part is the clogged CAT was actually found bad using the testing method described.

Click here

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medicmandan

A local muffler shop tested it for free. It was plugged. They'll have it replaced by the morning. $300 parts and labor.