Loss of power when hot (more problems)

I thought I had my problem licked when GM told me my TPS was bad but I replaced it and I still have a loss of power when the motor is hot and it is hot outside (over 85 degrees).

I notice that when I drive the car in the morning when the temperature is around 65 degrees, it runs like a champ. Great power, no hesitation and it climbs hills easily.

but on the way home from work in the after noon, when the temps are in the mid to high 80's, it has that same los of power feeling. the car doesnt like to go. at 65 and up, it feels like the pedal doesnt do very much until it kicks down. going up hills (even at 45) makes it kick down into 3rd or even 2nd sometimes.

what could be so temperature sensitive that it would do this? If I take it back to GM, do you think their scanner could diagnos this if they do a running (driving test) when its hot outside? Like I said, it runs perfect in the morning after sitting all night at 65 degrees and you can just start to feel the problem developing after the engine gets to operating temp but its not that bad when the temp is cool. when its hot, it is pretty bad.

(PS sorry bout the fuel injector controversy in my other post)

1. Check your IAC for proper function.
2. Check your EGR valve. You may want to swap it with a "junk yard" unit to test. I have now seen 2 of these electronic EGR valves test good when they were not. The EGR valve is much more active when the engine is hot.
Both of these checks are easy and replacement if needed is also easy. Good Luck.

Its Pretty common to develope this, there is a AIR TEMP SENSOR on the back of the air box that goes bad after a while which makes your car run lean when warm, also the oxygen sensors become " slow " after a while which will also lean out the car. when your car is cold it runs in a default mode which basically gives a fixed mixture that is pretty good for power. On a higher mileage vehicle it can also be caused by loss of compress from wear when warm. If you haven't tuned the car up recently do so.. I dropped my acual engine temp to a 180degrees via a 180 degree thermostate.. give me a little extra HP. How many miles are on the car and when was the last time you serviced your trans?

its definetly temp related. and its seems to be intermittant. I changed the oxygen sensor less than 15,000 miles ago when i put the rebuilt engine in (a long block).

Everything else has 193,000 miles on it.

its got GREAT power in the mornings for about the first 15 minutes and then, after it heats up it seems, it gets poopie. something is acting up.

its worse when its in the 90's out here.

its definetly temp related. and its seems to be intermittant. I changed the oxygen sensor less than 15,000 miles ago when i put the rebuilt engine in (a long block).

Everything else has 193,000 miles on it.

its got GREAT power in the mornings for about the first 15 minutes and then, after it heats up it seems, it gets poopie. something is acting up.

its worse when its in the 90's out here.


Well i would check your EGR valve and possibly ignition module and coils. now I removed my Air Intake Screen on the throttle body and also opened up the AIR box and I gained noticable HP and mileage. as for the lag when warm , the thermostat helped a bit. what i would do is check your compression when cold as in not run for the day and then check it once hot. if there is a noticable difference then you know its motor related.

here is another issue too, when the motor gets hot, it will begin to knock, so what the computer does is pull timing out of the motor, causing the lack of power... Try running super unleaded, see if it helps.. If it does then thats your issue as is mine too. todays gas sucks and motors are prone to detenation.

2 years later and the problem is fianally solved

It was the fuel pump.

I had checked the pressure at idle and it was 45 psi but apparently, when it gets hot there isnt enough gusto when the engine demands it. I took the car to a shop and told them everything I diud from changing vacuum lines to changing the vacuum resevoir (which did leak btw) to checking the fuel pressure, compression testing, tps changing etc.

the shop asked if I tried pinching off the return line for the fuel and I said no. they said the fuel pressure sould spike and if it doesnt its the fuel pump. I was hesitant to believe but sure enough, they changed it and it works like a champ.

2 years later and its solved. hip hip horray