intermit high idle is killing us

[250rider]

my wife has a 95 all stock 5.0,auto,gt

the car is runing at high idle 1500-2500 and is wearing out the brakes trying to hold it back.

but some days it dosent do it and idles perfect 500park/900drive(or is it the other way)it's late 3:30am.
dosent mater if its hot, cold, rain or shine. or if the car is warm or not.

the ford dealer has had it for 2 weeks and cant find the problem.says it dosent do it when they drive it.

its had a tune up,the tb cleaned, new stator & parts , new iac, tb adjusted by drilling out. the only code it give is a lean code that makes the check engine light come on in about 10min of driving.
I cleaned the maf with sensor eletrical cleaner, which has helped with a past 94 mustang but i failed to get the same results on this one.
I noticed that a previous owner had checked tbs voltage before, do you think even though good voltage it still might be bad.

guys please help me out, I have had more trouble out of our last 2 cars (94,95 mustangs) than anything we have ever owned.

 

[mo_dingo]

I had this same exact problem. It was very wierd. If the car sat for a while, the idle would return to normal. But once you killed the motor & restarted it, the high idle would come back.

There are only 3 things that can increase the idle speed of the motor. The throttle blade being open (which is easy to check), extreme vacuum leak (i.e. the brake booster hose is completely disconnected), or the IAC valve is toast, like mine was.

I removed my IAC valve to clean it, and in the process ended up breaking it (it didn't like the carb cleaner I guess).

When I went to autozone to buy a replacement, then one they sold was manufactured by wells. The instructions (at the bottom of the box, ) say to mount the new IAC valve backwards for proper function. Well, the OIL dipstick tube blocked it, so I couldn't. I tried to mount it normally, but the problem stayed the same.

I ended up getting one from Pep boys, which looked identical to the factory one (probably factory rebuild I guess). As soon as I put it on, it returned my idle speed to normal. Everything has been great since.

This is from my experience, and I surmise this is your problem. I don't get why the dealership can't figure this out (unless they used a autozone part & didn't mount it backwards). But I can't imagine Ford using autozone parts.

Try it and see what happens. Then make Ford eat the bill.
Scott

 

[250rider]

mo dingo,

a new one was put on 3 days ago, still doing it.
any other ideals?


ps,
went through this before with iac and I have only found that a a borg warner brand or oem would fit.

 

[94TURBO5 O]

You may need to change your ECT and o2 sensors.