it starts and runs fine most of the time but if i am city driving and stopping a lot the engine will pulse. Revving itself 100-200 rpm. and theneventually at one of the stops the car will sputter and rev the engine quite a bit, up to about 2000 rpm, and I will get a reduced engine power light. if I turn the car off and leave it for a while it will start and run normally again until it gets put in the circumstances mentioned above. I have been keeping a very close watch on the temp guage but it never gets above half way.

For some background, I replaced the fuel pump about 6 months ago. There is a very slow oil leak at the pan, i keep the oil topped off though. There is also a coolant leak that i havent been able to track down yet. The plastic coolant elbows were cracked so i replaced those and that slowed the leak down quite a bit but I am stiil losing some. Also there is no chech engine light on. I am gonna have it looked at but i would love any suggestions as to what this might be. Thank you.

 

It happened again and this time the check engine light came on. It threw P1516- throttle actuator control module, throttle actuator position performance.

P0137- oxygen sensor cicuit low voltage. Bank 1 sensor 2.

If any body could shed some light on what those mean I would appreciate it.

 

I am thinking it has something to do with the codes,,,, Always look at O2 codes last they tend to be results of the other problems.

 

In your model car the idle speed is controlled by the "drive by wire" TAC system. The TAC controls both idle speed and throttle valve opening. You may want to take a look at this link. P1515 P1516 Engine Power Reduced - Ask the GM Technician - GM-Trucks.com

 

The V6 does have a lot of problem with the drive-by-wire throttle system. The code you are getting does go along with the symptoms you reported. P1516 is indicative of a response feedback issue with the throttle control, sometimes caused by a defective throttle body. The problem with these codes, is that they are sometimes caused by other issues, since a rough running engine can cause other erratic readings. I would get a generic PC OBD2 scan program ($25) and watch the two throttle position readings while slowly pressing the accelerator pedal. They should match and be in smoothly-changing proportion to the amount the pedal is pressed.

 

The O2 sensor behind the cat is throwing a code. Then you're getting codes for throttle performance. This sounds like a plugged cat.