Thread: power loss when hot

Hello,

I just bought a 98 GTP, it had the engine light on since I bought it and the car would hesitate when accelerating, it would vibrate then take off. The tachometer sometimes would drop to zero and the TCS Off light would come up, but the engine would still run. Turning off the engine and back on again would fix the tach issue. The car was also wasting a lot of fuel. It had 16.5liters/100kms (sorry I only checked it on metric). The car would accelerate normally when cold, but once it got hotter all of these problems got worse specially when giving it full throttle.


I took it to a mechanic to check it out, he checked the wires, plugs and filters. He said they were still in good shape. The engine code was for the crank shaft position sensor. I also did some research on the web for these symptoms and I found out that they were also related to the CPS. We just replaced the CPS and most problems are gone: tach won’t drop to 0 and it’s no longer wasting so much fuel, it’s at 14 liters/100km now. But I still have the power loss issue when hot. When I give it 100% throttle the acceleration is erratic, the engine revs jump while doing this. If I only give it about 75% throttle it has a more decent response and even more power than 100%. Again, none of these symptoms appear when the engine is cold.

The ECM doesn’t have any codes so we are not sure on how to proceed next. The mechanic is recommending me to change the plugs, filters and clean the injectors next, but I wanted to consult here first for any opinions on what should my next step be.

The car odometer says 97,500 kilometers not sure if someone tempered with that, but the rest of the car is in very good shape so I don't really doubt it. The seller also gave me an invoice in which they bought a new engine from the pontiac dealer back on 2002.

Hope someone can help, Thanks!

Thanks for the quick reply. I agree that that would blow up the engine, I just did it a couple of times to see if the problem was related with temp. I also agree that the cat may be clogged. I was thinking it could be related to fuel pressure or the cat. How would I know if it's clogged? I've never actually had a car with a cat... I always took those out. I remember a friend's cat used to glow from the heat at night I used to think it was because it was clogged.

Update:

I've really had this car for just over a week now and on my way home I loaded high octane fuel instead of the regular that's been running on. Most of the problems are gone now by doing this, there's just little hesitation but almost not enough to bother me. The fuel consumption went lower too, from 14lt/100km to 13.5lt/100km I'm not sure if the supercharged model is supposed to be running on premium only, but I just went through Reptile's sticky on octane and read that low fuel delivery can create detonation on supercharged engines. I'm more inclined to testing the fuel delivery system instead now. I'll drop by the mechanic tomorrow and test atleast the line pressure, how much is it supposed to be on the GTP? 50lbs?

Any opinions are appreciated. Thanks!

HAHA it probably does, the thing is that in Mexico we rarely pump our own gas. There's always someone who does that at all gas stations. I'll look inside the cap cluster later.