Ford F150 1994 - Idle problem

Hello,

A friend of us has an EFI 1994 F150 truck and he does have idle issues.

The ilde could stay normal then it goes 200rpm more, sometimes 400rpm more. What could affect this? Vacuum leak?

Thanks


Dylan

Originally Posted by Sponge

Hello,

A friend of us has an EFI 1994 F150 truck and he does have idle issues.

The ilde could stay normal then it goes 200rpm more, sometimes 400rpm more. What could affect this? Vacuum leak?

Thanks
Dylan

It could be a whole bunch of thngs. Find or purchase a scanner/code reader for the EEC-IV it'll give you a jumpstart on where to start looking. Generally, these kind of problems start in the emissions control areas. As these engines start to age, a lot of EGR ports start to clog with carbon - which makes the computer have to guess instead of reading the sensors. I don't know what Ford code readers cost over there, but they aren't that expensive - but are sometimes difficult to find, especially since the newer engines (since 1996) are running the OBD II specification / EEC-V computers.

Thanks Beowolf.

He went twice to a guy who plugged a computer and no errors were found...

Out of range sensors will not trip a ford to place codes unless it's MAF or O2 sensors out of range, that type of thing. Evap is either a working or not working system form my own experience.

Clean the seating on the IAC motor, then make sure all the wiring and sockets are in good condition.

Here's a bit more explaination.

When the engine is hot, the idle increases 200rpm + and stay. A quick gaz pedal hit and the idle drops 200rpm. A couple of minutes after, same issue, 200rpm +

We think an IAC failure, what do you suggest? How can we make sure that motor is in bad shape?

Thanks

Here's a pic of da beast. The engine is liquid gaz injected.

Originally Posted by Sponge

Here's a bit more explaination.

When the engine is hot, the idle increases 200rpm + and stay. A quick gaz pedal hit and the idle drops 200rpm. A couple of minutes after, same issue, 200rpm +

We think an IAC failure, what do you suggest? How can we make sure that motor is in bad shape?

Thanks

If you think that is the problem then replace it ... they cost between $30 to $40 + . Ford sourced 2 or 3 versions of them over the years. They are "not" supposed to be cleaned, but some folks do it anyway and they start to work. My personal suggestion - ain't ready to argue about it - is replace the unit. Clean the passages ways in the throttle body too.

The units have an electric motor (solenoid) which moves a plunger/valve that opens and closes the IAC to allow more or less exhaust gas into the intake. That "bypass" is what sets the idle up or down. It also feathers the throttle during braking to keep the engine from stalling. 'least ways, thats the way I heard it.

If you have futzed with it more than once or twice, its cheaper to just replace it and get it off the list, out of the way so you can focus on something else.

If you really want to trouble shoot it... get a Haynes or Chilton manual. They are supposed to have expeted voltages that you can check for (using a DVM) so you can be sure the right signals are coming in. I don't have a lot of free cash either, but some parts are just not worth messing ith too many times. Especially on a high miles engine which still has original electrical parts.

Before replacing the IAC motor think on this. The motor is obviously working or the truck would run like crap.

What is making the IAC motor give those additional rpm's?

What decides the IAC position in a Ford motor?

Now once that's know then make your decision on what to replace.

It is common for these to get dirty and I clean them all the time. DO NOT use carb cleaner. Use a detergent or top engine cleaner. Also take a soft brush and same to solution to ceal throttle plate and bore. If you are handy with a volt meter I will walk you through testing the throttle position sensor. These go bad alot and cant be cleaned.

I made a mistake, it's a 1992 F-150.

Do you think we can find a technical manual in french in Canada about the EFI?