Engine Idle Is Erratic

DAMIEN256

MEMBER
1989 FORD F-250
V8
4WD
MANUAL
147,000 MILES

Hi guys, I have a 1989 5.8L and the idle is all over the place. I did a major tuneup, changed TPS, AIC and it still has the same problem. When at idle, (no load), the engine just will not idle at one speed. The RPMs are always moving up or down, 800 to 1300 to 900 to 1200 to 900 you get the idea. It will not stay at one RPM for more than a second or two. Can some one please steer me in the right direction? PLEASE? I am at a loss as to what it might be. Any help would be appreciated. I asked for help earlier and was recommended to change TPS and AIC which I did. Thanks for any help.

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

When was the last tune-up?

Check engine compression, PCV and EGR valves, Vacuum leaks

This guide should help you

https://www.2carpros.com/articles/a-comprehensive-guide-to-diagnosing-and-fixing-erratic-engine-idle

Please go over this guide and get back to us.

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Monday, January 26th, 2009 AT 10:24 AM

DAMIEN256

MEMBER
3 POSTS

3 days ago I finished a major tuneup on it. There are vacuum hoses all over the place. Is there an easy way to check for vacuum leaks?

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Monday, January 26th, 2009 AT 5:15 PM

RASMATAZ

MECHANIC
75,992 POSTS

Use WD40 and spray into the areas of the intake manifold/base of throttle body/vacuum hoses when the idle smooths out you've found the leak or use a stethoscope to track the leak by the hissing noises, or the propane and scantool method

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Tuesday, January 27th, 2009 AT 1:00 PM