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1988 Ford f150. HIGH idle
07-25-2017, 01:33 AM
Post: #1
1988 Ford f150. HIGH idle
This truck runs wide open if you crank it. To the point it can't be moved, because if you put it into gear it's not going to stop. It IS fuel injection. We've replaced several parts.
Throttle position sensor
Vacuum lines
Plugs and wires
Throttle cable
Throttle valve body

Nothing has made the slightest change. Any ideas?
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07-25-2017, 06:30 AM
Post: #2
RE: 1988 Ford f150. HIGH idle
Have you checked the simple things first? Like I have seen the gas pedal stuck to the floor mat, or froze to the floor, or stuck in mud on the floor. Is the throttle return spring broken? Is the throttle cable stuck.

Have you looked in the throttle body to verify if the throttle plates are closing?

A little more information could help us come up with some better answers so please get back to us with more details.

Thanks for using the forum,
Garner

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07-25-2017, 01:20 PM
Post: #3
RE: 1988 Ford f150. HIGH idle
All of the things in the first paragraph have been checked.
The whole throttle body was replaced, but no we didn't check to see if they were closing on the new one. They WERE closing on the old, one, but I was told that part of it was bent and needed replacing and that that was causing the problem. That was not the case.
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07-25-2017, 07:37 PM
Post: #4
RE: 1988 Ford f150. HIGH idle
First you should confirm that the throttle plates are closing. Unless that is the "Variable Venturi" model that I think was used around that time? Then the venturi must close at idle.

If none of that is the problem then you need to look for another rout for air to get into the engine. Vacuum lines are a first suspect. A broken, disconnected, or missing line can cause air to enter the engine just like opening the throttle. Especially a large line like one to the brake booster. A leaking brake booster can do it too. Other suspects would be the EGR valve, the intake gasket, or a cracked intake manifold. The throttle body gasket itself could be damaged and leaking so check it too.

Please let us know what you find.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
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