Question about 1997 Pontiac Grand Am
Will surge as much as 1000 RPM's when in Neutral and pressing gas to between 3000 and 4000 RPM's. Stalls at a stop inermittantly. When car is accellerating the fuel connection is fine. When you attempt to maintain a speed (not accelerating or decellerating) the engine shudders and shakes.
Surging is often caused by a bad sensor in the air/fuel supply - MAP, IAC or TPS. Check for trouble codes (DTCs) using a good code reader.
Posted on Feb 09, 2018
sounds like your IAC (idle air control valve) located on the throttle body towards the front of the engine held in by 2 torx screws. the iac controls the idle if the car when your not on the gas. i will post the steps to clean the iac and the passages that the iac goes into.
1. disconnect the iac connector
2. remove the iac
3 clean the iac pintle valve and check for wear
4. clean the passages that the pintle valve sits in (usually carbon build-up in there, you may need to remove the air intake tube and air filter box to get to the passages in the throttlebody)
5. if the iac looks ok and the passages are cleaned re-install and put everything back
6. start car and see if it idles like normal when warmed up. you may need to give it a few tries for the iac to re-learn its proper position so give it a few warmup cycles
7. if it still stalls check for proper operation of the iac via ohming out the connectors (if you look it up on google you will find the specs at which the iac is supposed to operate)
8. if the iac is working properly, check for vacuum leaks on the intake manifold and vacuum lines.
9. if no vacuum leaks are present and the iac id working properly after cleaning have a shop check the ecm (engine control module) for a bad circuit board, i've seen that haoppen as well
hope this helps!
Posted on Feb 17, 2009
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