speed density..won't idle below 1100 rpms...

[v8only]

Hello all!!! Well, I was lucky enough to score an 86 ssp x chp mustang coupe, and I've been putting some wrenching time into it.

It runs and drives like a dream, except it won't idle below 1100 rpms. Being that it's speed density, first thing I checked was vacuum. I did find some leaks, and buttoned it all up, and get a VERY steady 20 pounds of vacuum now.

I also set the tps, and it's sitting at .97, and have tried swapping out with several known good IAC's. Lastly, I tried backing out the idle screw and set timing to 12 degrees, but no effect either.


any clues?? I've gone through all the basics, and the problem still persists.

 

[ninety15.0]

Im not sure how the MAP sensor effects idle...but im sure SD cars are very sensitive to changes in manifold pressure. Perhaps you should test out that MAP sensor...and replace if necessary.

Have you gone through the surging idle checklist?! That would be my next step!

 

[Rdrcr]

Since the weather change, my '86 GT has been idling around 1,100 rpm too. However, after a short-medium length drive the idle will settle down at around 800 rpm. It seems that the cooler weather has definitely affected the idle of my car.

Mike

 

[Darkwriter77]

Same issue here. It's like it won't get out of cold idle mode, or something.

Dunno if it's related to the issue or not, but when I back out of the drive and go from reverse to drive, it stumbles like it'll almost stall for just a second and then it picks back up right away - it'll do it once, only right after starting, doesn't matter if it's on a hot or cold start.

 

[FrankenStang]

Same issue here. It's like it won't get out of cold idle mode, or something.

Dunno if it's related to the issue or not, but when I back out of the drive and go from reverse to drive, it stumbles like it'll almost stall for just a second and then it picks back up right away - it'll do it once, only right after starting, doesn't matter if it's on a hot or cold start.

Wait till it does that phantom idle surging crap on ya... Kinda spooky.

 

[HISSIN50]

Jeremy, till it's sorted out, how about just fabbing up a restrictor plate over the IAC boss?

It'd bandaid it for you till the issue changes, fixes itself or gets worse. I personally think that with cars like this, issues like this one often change as you get some miles on the car. I dont go nuts trying to fix problems till they have persisted through a couple tanks of gas.

Nice pick-up and good luck brah!

 

[v8only]

Thanks!! We scored the chp car for $1200 running with a low mile 93 motor installed.

will that iac plate that was put on some fords for a fix work?

 

[HISSIN50]

I'm not sure on the idle plate - I have not used one on a *SD* stang yet.

Before doing that, I would confirm that the idle doesnt drop when the IAC is disconnected. If so, it still sounds like an IAC issue. Then using the plate would be like having shoes that are too big, so you buy really thick socks. Better to just get the correct sized shoes.


That really does sound like a nice pick-up mang! The wife must love all the stangs around the house. "No honey, the CHP stang will make a nice conversation piece in the living room..............."

 

[v8only]

I don't think it did drop, but it worked fine in my car....I'll have to wait until the next time I get to the car.

the ssp was one that I could not let go. I've been wanting an ssp coupe forever, and the 86 is my favorite year. I had to jump on this one...however, the only way I could pick it up, was to have my father pick it up...so it's at his place, and he drives it around. the title shares our name, but I promised my wife I wouldn't bring another home. 2-3 months ago, I got fed up with all the old car bs, and dumped my 78 bronco project, and picked up a fully loaded quad cab blacked out Hemi ram, so another mustang was certainly out of the question.

2 weeks afer I had the ram, the flowmaster went in, lol. My wife still passes comments on the ram, as I have a company vehicle, and am now making payments on a vehicle I drive maybe 4k a year...lol I deserved something nice damnit!

I'm going to see my father this thursday, I took the day off so I can finish putting the dash and interior into my 86 vert, so I'll check out the ssp idle, and post back then.......

our $1200 ssp coupe after some cleaning up, sporting the only police wheel left...(I need to find some more)

tan interior too!

and the beast... sorry to turn this into a pic thread, I haven't been around for a while

 

[HISSIN50]

Your poor wife.
She is definitely a keeper!

Nice rides Jeremy. Some of us don't have newer cars (or trucks) so we have to be envious of those that do have 'em. The truck looks like fun.

 

[jrichker]

See "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.