2001 Pontiac Aztek

Engine Performance problem
2001 Pontiac Aztek 4 cyl Front Wheel Drive Automatic 154, 00 miles

My problem just occured today. As I was leaving the store I approached the red light and when I braked to stop, my car started to rev up to 3000 rmps and would not stop. I live 12 miles away from the store I was at and at every stop sign or light, my car would slow down normally and then when I was at a complete stop, the rpms would jump and it was if I had the brake and gas on at the same time! What the heck could be causing that?
October 14, 2009.

If you haven't had it looked at yet, a scan tool that shows engine data will be the primary source of your diagnosis. Barring the basic checks, floor mat wedged on pedal, giant vacuum leaks from the engine making a loud hissing noise or the air filter lid left off of course.

If you can get access to a scanner check the throttle position sensor position (tps) first. At a stop with your foot off the gas it should read 0.0 volts. If the engine sees the sensor too high it believes the gas pedal is being pushed and will compensate by adding fuel, which causes the idle control to compensate for near stall from a rich condition and you have a high engine revs.

Post back if you need further assistance.

Good luck.

Nov 18, 2009.
Thanks for the reply. The actual problem was coming from the idle arm control motor. It was very dirty and once cleaned and put back together, my problem stopped. I ended up putting a new throttle posistion sensor on it anyways because I already purchased it.

I have a new problem now. Car overheats after one mile of driving it, the radiator cap doesn't get hot, it is leaking a small amount of antifreeze. The heat works and then it doesn't. I am not sure why the engine gets so hot so quickly. The antifreeze overflow isn't being used when the engine overheats. Could my thermostat or water pump be going?

Nov 19, 2009.
Excellent work on the Idle Air Control! I am certain we can figure this new problem out. We'll start with a couple of checks and questions to get started.

1) Does the overheating occur after 1 mile even when started cold? (Has sat for at least 3 hours)
2) Is the overheating symptom the gauge, and if so where is the needle rising to?
3) Is the overheating symptom steam from the engine?
4) What are the coolant levels for the radiator and overflow tank? FYI the overflow tank often looks as if it has fluid but is just a small bit that wouldn't drain. You can verify if fluid low in the radiator by filling and noting how much it needed. Add slowly and allow time for air to escape.
5) If the fluid is about 1 gallon low, pressure test the system with a pressure tester while the system is full and inspect under the hood and on the ground for the source of the leak.

Here is a site link for the basic coolant checking.

I've probably overloaded you for now so, post back and we will proceed with the diagnosis.


Nov 19, 2009.