Checked IAC - still will not idle
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Freshman User
Joined: Mar 2004
Posts: 28
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Checked IAC - still will not idle
Ford 1989 5.8 E-150
After a rebuild, the engine runs well, for about 20 seconds.
Replaced the ignition coil, checked the IAC... The van won't run long enough
to use the code reader.
What could be the problem?
Find20
After a rebuild, the engine runs well, for about 20 seconds.
Replaced the ignition coil, checked the IAC... The van won't run long enough
to use the code reader.
What could be the problem?
Find20
Laughing Gas
Joined: Mar 2003
Posts: 877
Likes: 1
From: Colorado, U.S.A!
No key-on-engine-off codes? Can you keep it running with the accelerator? How's the fuel filter? Checked fuel pressure? Might be good to hook up a fuel pressure gauge and see what it does right before the engine dies.
All I can think of right now...
All I can think of right now...
Senior User
Joined: Oct 2003
Posts: 321
Likes: 0
From: Metamora
I'm suprised that you couldn't check the trouble codes with the engine off. The computer should store the codes so that you can check them with the engine off and the key in the on position.
It is too tought to say what could be the problem without knowing what the computer is telling you, any number of sensors could be giving the computer the wrong information (such as the MAP sensor or TPS), or it may be as simple as a cut vacuum line.
I had problems with my 91 5.8 on startup last winter, it turned out to be a dirty IAC valve, after a brief shot of carb cleaner to remove the carbon, it worked fine. If yours is clean you may have a different problem. You may also want to make sure that the gasket between the IAC and the throttle body is in good shape, an air leak between the IAC and TB interface may cause problems. Also a torn or partial gasket between the TB and the intake manifold may cause an idle problem.
It is too tought to say what could be the problem without knowing what the computer is telling you, any number of sensors could be giving the computer the wrong information (such as the MAP sensor or TPS), or it may be as simple as a cut vacuum line.
I had problems with my 91 5.8 on startup last winter, it turned out to be a dirty IAC valve, after a brief shot of carb cleaner to remove the carbon, it worked fine. If yours is clean you may have a different problem. You may also want to make sure that the gasket between the IAC and the throttle body is in good shape, an air leak between the IAC and TB interface may cause problems. Also a torn or partial gasket between the TB and the intake manifold may cause an idle problem.
Senior User
Joined: Dec 2003
Posts: 354
Likes: 1
From: Memphis, TN USA
Do you hear any loud hissing noise. Probably, the hissing noise is being muffled by the engine noise. The hissing noise is usually vacuum leak that is getting pulled in into the intake.
Try to disconnect and plug the vacuum hoses that is not necessary when the engine is at IDLE and not moving. You can try to remove the brake booster vacuum hose first and plug it (don't try to drive the vehicle with the brake booster vacuum hose disconnected because you will have a hard time trying to apply the brake pedal.)
I've read some thread that some folks disconnected the power cable to the IAC and their IDLE doing fine.
What happens if you push the gas pedal during the 20 seconds time frame? Does it continue to run with gas pedal pushed down a bit?
Try to disconnect and plug the vacuum hoses that is not necessary when the engine is at IDLE and not moving. You can try to remove the brake booster vacuum hose first and plug it (don't try to drive the vehicle with the brake booster vacuum hose disconnected because you will have a hard time trying to apply the brake pedal.)
I've read some thread that some folks disconnected the power cable to the IAC and their IDLE doing fine.
What happens if you push the gas pedal during the 20 seconds time frame? Does it continue to run with gas pedal pushed down a bit?
