1995 FORD F150 starting hot or cold, idles extremely high?

Question

truck will idle high for approx 1 minute. Then will sputter and act like it is going to die. When driving you can feel and watch the rmps bounce up and down. What could be the cause of this. It is fuel injected 5.8 xlt. Has been in the shop and no ones seems to know what it is. I have tuned it up, sent the computer out to be checked and replaced what I thought was the I.A.C. deperate and need help. This weekend I am just going to start tearing it apart piece by piece to see I can figure something out.

Answer 1

Just did an 5.8L engine in a 92 & most of the vacuum lines on the engine we rotten, especially the two that enter the throttle body. The one for PVC Valve is a little tricky to get at.

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Answer 2

Could have bought a bad I.A.C.there's also anther part that runs in conjunction with the I.A.C. it has to do with the vacuum,also it could very well be the throttle position sensor.Where ever you are going change I've never heard of sending the computer anywhere without the truck to read any other sensors problems going on.Look for a shop that has the equipment to analyze.Ask if the have a Nemesis or Genesis,those type of shops know what you are talking about.

Answer 3

Hi,,,,It sound's like you have a vacuum leak at the intake gasket,Ford5*8 are known to blow out the plenum gasket,,also,,have the PCV valve inspected,,as these,,too, cause the problem you described...It is located at the very rear of the engine,..Make sure that the hose,valve,and grommet are in good shape cause these are all connected,,,Good luck!!!!

Answer 4

idle air control could be the problem IT IS NOT A VACUUM LEAK BECAUSE IF IT WAS THERE WOULD BE A HISSING SOUND

clean out your throttle body

get your spark plugs and plug wires changed

Answer 5

sounds like a intake manifold vacuum leak..
the manifold is a two part design..
the gasket between the halves has probably failed

Answer 6

Vacuum leak?