Hello,

I was recently experiencing what I would call Bucking when the car was idling, and when the car was accelerating at a low speed < under 20, then it smoothed out above 20 Mph. all of a sudden my check engine light popped on I was happy to see this (now I can get a code) so I took the car to Auto Zone, and ran the scanner on the car, and the coil pack (1 and 4) was misfiring causing an issue. P0304 after buying the replacement part and installing it, I drove car for a few days it was good, then It papered to start acting up again. so I took it to a local shop to have a person look at it, they told me that the plugs, and wires were shorting out by the base on the block barley noticeable but it was causing a shot. so I paid them to go ahead and replace all 6 spark plugs, wires as well as the other two coil packs with AC- Delco parts. again the car ran fine again for 2 days, then heavy rains came, and the problem came back the next day, not near as bad as a misfire but clearly the idle speed was fluctuating between 500-1200 ish. I took car back thinking that there was another issue possibly the EGR valve. But they took another look and said it worked great. That day I picked up my car, I drove it home and no sooner than i got it to my driveway it started to act up again???? Well this time. I pulled out the Haynes Book and flipped to page 4-12 looking into the IAC valve, or the Idle Air Control valve. I am curious if this can be the cause of the mysterious phase in phase out of idle related issues that I am experiencing. Any help would be great, the car still drives but can be a rough idle at times. Could there be a sensor that is causing this to be out of whack such as an oxygen sensor?

Thanks,

Jacob

 

I just had to replace my IAC valve on my 2005 Monte SS supercharged 48,846 miles because it was idling up and down but not all time.. hope this helps..

 

Thanks, by the way my car is a 1999 monte carlo 3.1 v6 with 175,000 miles. I don't know why I didn't state this earlier. So how bad was the throttle responce before the replacment of that part?

 

Could be Throttle Position Sensor, MAF sensor, O2 sensor