1990 F-250 idle problem

Reply Subscribe

Thread Tools

Search this Thread

Dec 3, 2012 | 12:42 PM

limaloco4

Thread Starter

New User

Joined: Dec 2012

Posts: 2

Likes: 0

1990 F-250 idle problem

Hellow, I need some help. I have a 1990 F-250 with a 5.8 under the hood with a manual transmition. I have the isue of when I let off the gass and push in the clutch the idle will stay high (usually 1200 to 2000 rpm) for a good 8-10 seconds and then slowly drop to normal. I can even do this in nutral and not even need to touch the clutch, just push on the gass to pring the rpms up and they will stay again for a good chunk of time. I know this is not normal as my dad's F-350 does not do that. Any ideas as to what could be causing this? I have a feeling it may be some sort of electrical issue but really don't know ware to look.

Any and all help is very much so apreciated!

Thank you

Andy

Dec 3, 2012 | 01:45 PM

Mike1

Lead Driver

Joined: Mar 2006

Posts: 6,259

Likes: 438

From: IL

Check you accelerator cabling to make sure that it isn't sticking, binding or dirty. Then check your IAC.

Dec 12, 2012 | 09:44 AM

limaloco4

Thread Starter

New User

Joined: Dec 2012

Posts: 2

Likes: 0

The accelerator cabling is all happy, no sticing or binding. What is the IAC and ware is it located? I am asuming it is a sensor?

Dec 12, 2012 | 10:15 AM

SCRebel

Fleet Mechanic

Joined: Jun 2011

Posts: 1,324

Likes: 3

From: Conway, South Carolina

IAC- Idle Air Control. Located on the side of the throttle body. Easiest was to explain it, It is a sensor that controls the amount of air flow going around the butterflies.

Dec 12, 2012 | 03:17 PM

Mike1

Lead Driver

Joined: Mar 2006

Posts: 6,259

Likes: 438

From: IL

Quote:

Originally Posted by SCRebel

IAC- Idle Air Control. Located on the side of the throttle body. Easiest was to explain it, It is a sensor that controls the amount of air flow going around the butterflies.

Thanks SCRebel,I sometimes forget that some people may not know what these components are or where they're located. I usually have my service manual handy if I need to look up locations of these things. The Manual is my bible...lol

Dec 12, 2012 | 11:34 PM

SCRebel

Fleet Mechanic

Joined: Jun 2011

Posts: 1,324

Likes: 3

From: Conway, South Carolina

No problem Mike1, happy to help.

Dec 13, 2012 | 08:48 AM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,786

Likes: 1,751

From: Kentucky

Quote:

Originally Posted by limaloco4

The accelerator cabling is all happy, no sticing or binding. What is the IAC and ware is it located? I am asuming it is a sensor?

The Idle Air Controller (IAC, aka IAB and a host of others) is not a sensor. It is a mechanical device actuated by an electric solenoid. It's operation is controlled by the Powertrain Control Module (PCM aka computer).

It is located on the side of the throttle body: