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Help with surging

T

txmtb

New member
Having an issue with a 2000 Grand Prix GT. When the car is cold, it runs great with no issues. After it is driven for around 30-45 minutes it starts to get a surge when you let off the throttle. During the first part of driving it, when you let off the throttle from 50+ mph the rpm will drop to ~1500 while coasting, and then drop down as you apply the brakes to stop and come to rest ~800 at a stop. After the engine is hot, when you let off the throttle, it will drop to around ~1500, then suddenly drop to below a 1000, then surge quickly back up to 1500. It will do this 4-5 times every time and then stop when you get below ~25 mph. Even while applying the brakes you can see and feel the surge. I did the TCC check by pressing the brake while it was engaged and it releases and re-engages with no problems. It also does this if I slide into neutral while coasting and slowing down, of course you can't feel the surge in neutral but you can hear it and the rpm gauge jumps from ~1000 to 1500. The only codes they pulled were for the oxygen sensor which was replaced. Otherwise the car runs great. Anybody had anything similar?
 


Checked today and it does it with the air conditioner on or off. I cleaned the throttle body and MAF today along with filter change to see if it will help any. MAF was pretty dirty. Will see if that helps tomorrow while going to work. Had them pull codes again today and there was the O2 sensor present, so assuming the Check Engine light doesn't work.
 
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