87 5.0 Idle Surge Help

[deftsound]

Long time no see guys. REcently picked up an 87 gt that has an idle surge. I have done my research and replaced the IAC, TPS, 02 sensors, all to no avail.

The wierd thing is when i press in the clutch pedal it goes away. Any ideas? Could it be my fuel pressure regulator. The car runs great at WOT, but below 1500 rpms its a total pain in the butt to drive.

 

[mikestang63]

did you run joe's (jrichkter) surging idle checklist? That would be the first place to start.

 

[deftsound]

Not yet. Some of that stuff is kinda technical if you don't exactly know what you're doing.

Also, the surge only happens when the engine is warm.

 

[jrichker]

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 134,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

Be sure to dump the codes, both engine not running and engine running. The procedure is in the checklist.

 

[deftsound]

Jrichker i appreciate your help.

However, I'm wanting to know if anyone has any ideas off the top of their head as to why it would only surge when the car is warmed up. Also I have no CEL light.

 

[jcgafford]

Cel lights do not light up with all codes. Mine had at least a dozen with no light. Dump the codes.

 

[mikestang63]

Jrichker i appreciate your help.

However, I'm wanting to know if anyone has any ideas off the top of their head as to why it would only surge when the car is warmed up. Also I have no CEL light.

It could be a dozen things. Run the codes and report back what they are.

 

[jrichker]

The no surge until the car warms up is because when the engine is cold, it runs in open loop with some presets and does not use all the sensor data. When the engine warms up, it switches to closed loop and all the sensor data is used to compute the running parameters. That's when a bad sensor or bad connection can mess up a perfectly good running engine.

 

[madspeed]

^^^ this

 

[Grabbin' Asphalt]

^^^2nd this, Closed loop playa!!!
Could be any sensor contributing to this, ECT, ACT, MAF clogged, Throttle body build up....etc