86 Mustang Idle Surging problems

[seibman]

My 86 GT Mustang with a 5.0 engine keeps surging while it idles, I have replaced the TPS, IAC, Fuel regulater valve, cleaned the fuel system, checked the timing and checked for possible vacuum leaks. Everything seems to check out, except for the surging problem at idle, its driving me freaking nuts!! Any help would be much appreciated!!

 

[Kdubslugga]

Ohhh been there done all that my friend!!! Few questions. When does it do it the worst? Cold engine or Hot? Does it do it all when the motor is hot? I had the same exact problem, and I replaced the MAp sensor and ACT at the same time and it fixed it. Not saying this will be your problem, but this is what fixed my car.. Also, how modified are you? Pretty stock? Speed density or Mass air flow? I assume its Speed density, since it is an 86 but you never know!!

 

[Kdubslugga]

Also check out, jrichker "surging idle checklist" its a sticky thread on here, it is a brilliant thread!!

 

[jrichker]

As suggested...

See the "Surging Idle Checklist for help with all your idle/stall problems. Everything you need to find and fix idle problems is in there.

The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

 

[seibman]

Ohhh been there done all that my friend!!! Few questions. When does it do it the worst? Cold engine or Hot? Does it do it all when the motor is hot? I had the same exact problem, and I replaced the MAp sensor and ACT at the same time and it fixed it. Not saying this will be your problem, but this is what fixed my car.. Also, how modified are you? Pretty stock? Speed density or Mass air flow? I assume its Speed density, since it is an 86 but you never know!!

It's worse when its cold, it does do it somewhat when the engine is hot. The motor is stock ( my wife wants to keep it that way)