idle control ?'s

Reply Subscribe

Thread Tools

Search this Thread

Aug 17, 2004 | 09:11 AM

beastybronco

Thread Starter

Senior User

Joined: Jul 2004

Posts: 351

Likes: 0

From: Arkansas

idle control ?'s

i have a really high idle since ive been having timing problems, the timing is now worked out but the idle is too high to drive

it has a new tps, and i just cleaned the throttle body and replaced tb gasket

but when i was working on the timing it backfired some could this have messed up the iac? the egr hasnt been functional in long time but it always ran fine without it so i dont think thats it, could i have suddenly developed a huge vac leak? all the ignition componets are new(coil,module, + complete tune up)
what controls the idle speed? is it just the computer and what sensors does the computer use

88' bronc 351w efi
i believe it has the standard eec-IV
thanx for any help

Aug 17, 2004 | 06:44 PM

1991_f250

Junior User

Joined: Dec 2003

Posts: 75

Likes: 0

From: Port Coquitlam

Check for a vaccum leak between the upper and lower intake it's a very common problem on these trucks with the 302 and 351 we do them at work all the time and ive had to do it on my own truck also. if you want to check it for leaks take wd 40 or carb cleaner and spray it on the manifold where they meet if the idle changes chances are thats where your leak is

Aug 18, 2004 | 08:59 AM

beastybronco

Thread Starter

Senior User

Joined: Jul 2004

Posts: 351

Likes: 0

From: Arkansas

would it happen all of a sudden

Aug 18, 2004 | 06:53 PM

1991_f250

Junior User

Joined: Dec 2003

Posts: 75

Likes: 0

From: Port Coquitlam

Mine began all of a sudden and my truck began idiling between 1100 and 1500 rpm the Iac motor controls the idle but if you have a vaccum leak it does not have the ability to bring the idle back down.

Aug 18, 2004 | 06:54 PM

beastybronco

Thread Starter

Senior User

Joined: Jul 2004

Posts: 351

Likes: 0

From: Arkansas

thats not even close its idling like 3000

Aug 18, 2004 | 06:57 PM

1991_f250

Junior User

Joined: Dec 2003

Posts: 75

Likes: 0

From: Port Coquitlam

It still must be a leak i don't think the IAC has the ability to hold that high of rpm your leak just may be bigger than mine.

Aug 19, 2004 | 04:21 PM

lmadore

Senior User

Joined: Jun 2004

Posts: 353

Likes: 3

From: Mid-Missouri

Sounds like an intake leak or a vaccum leak at the intake.
Mine (86/5.0/EFI) started idling real fast all of a sudden.
It turned out to be the gasket between the upper and lower intake.
Aluminum and cast iron expand and contract at different rates when heated and cooled. Makes it difficult to maintain a good seal.
The gasket was original up until this summer. When I went to replace it, the old gasket had several obvious places where it had lost its seal.