87 Gt Idle Problems

[allen87gt]

I have a stock 1987 Ford mustang GT, only mods are under drive pulleys and electric fan. When I start the car in the morning and its cold the idle will go up to 1500rpm for a second and then drop to 1000 and then the idle will surge from 700-1200 until the car warms up, then once the car warms up the car idles high at around 1200 rpm, and if I pull the spout connector it goes down to 1000rpm. My timing is set 10 degrees.

Also I have tried checking TPS I am getting the right voltage, and also I tried disconnecting the IAC with the engine running and the engine shuts off, don't know if that's normal or not because when they recommend to try that they talk of the engine sputtering or smoothing out.

Update - Pulled some codes
ON KOEO got codes 54, 34 and under the stored codes I got 11
With KOER I got 98 then 54

 

[General karthief]

There is a surging idle checklist that should help in the tech/how to threads, I will post a link.
Thanks to jrichker and others for this helpful thread.
http://forums.stangnet.com/showthread.php?t=698148

 

[General karthief]

I will add that the underdrive pullies cause charging and cooling problems and should be avoided on street driven stangs, I am also guessing you have a good tuneup and checked for broken, soft or hard/cracked vacuum lines

 

[allen87gt]

I will add that the underdrive pullies cause charging and cooling problems and should be avoided on street driven stangs, I am also guessing you have a good tuneup and checked for broken, soft or hard/cracked vacuum lines

ive been through the issues on the under drive pulleys causing charging and cooling problems which I don't actually have with everything I'm running on my car, I have a 130 amp alternator, 12in dual electric fans, a aftermarket 2row aluminum radiator and a 160F thermostat. Car has new distributor, cap, rotor, plugs, wires, ignition coil, fuel pump, fuel filter. I'm planning on replacing all my vacuum lines to try to get rid of any vacuum leaks even though I tried checking for leaks and found none. Also not sure if this is normal because I heard the EGR should have no vacuum at idle but mine had a very small bit of vacuum.

 

[Dan02gt]

Yes the EGR should not have any vacuum at idle. If it does that can cause idle issues.

I would also ditch that 160* thermostat for a factory 192*. The ECU is expecting the car to run around 190* and if it doesn't reach that temp it can cause driveablity issues.

 

[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. It includes how to dump the computer codes quickly and simply as one of the first steps. 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 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.