Just bought my first f150, its an 89, i got it for 600 bucks, it seems to run good the only problem i find is the idle speed seems way too high. I knew nothing about these trucks until today after I bought it. It has the EEC-IV system. does anyone know what causes this, do I need to have it checked or is it something I could do?THanks for any imput.

 

Which engine and which transmission do you have?

 

5.0 V8 automatic.

 

Clean tha IAC, then do the idle re-learn procedure for the 5.0. Here's a link with more info.
http://www.muscularmustangs.com/iac.php----IAC
http://www.muscularmustangs.com/idlereset.php----idle reset

 

I don't agree with that idle reset article - you should NEVER adjust the throttle stop screw, unless you think someone already has, and you're trying to put it back where it belongs.

Also, there's no reason to mess with the IAC until you've checked for other problems first. Most importantly: vacuum leaks. Those V8s are known to suck in the plenum gasket on the R rear, which is under the plenum & kinda hard to get to. But you can use a 3' piece of garden hose as a stethoscope to pinpoint any leaks with the engine idling. Listen at the air filter intake to hear what it'll sound like, then check the rest of the intake for that sound.

This thread explains in detail how to pull EEC-IV codes with only a paperclip, but some people find it hard to read. You can either skip to the colored text, or there are several other articles that might be easier to follow. I know FordFuelInjection.com has a popular one.

Another mod that I always recommend for those trucks is described in this thread.

And you should buy one of these, and a decent digital multimeter (DMM).

 

thanks for all the info, I will visually inspect everything as good as I can for cracks leaks etc. from there not really sure what to do, all these tests im not sure about. I had never heard of this EEC system before, I figured when I bought it I would just have to adjust the idle a bit thats what I get for thinkin i guess. And that manual you recommended, I picked one up before Icame here and it doesnt go into detail about the EEC system or how to repair it. Again thanks for the help

 

Then you don't have that one because it goes into GREAT detail. The PN is 36058 & you'd be better off with the latest edition with the light blue cover.

 

ALright Ill find that one thanks.

 

Another question. If there is a problem with the EEC system should the check engine light be on, its not.
thanks

 

There's a set-screw on the throttle-body that you can adjust to raise or lower the base idle. It takes a flat-head screwdriver, but a penny will work too.

 

this throttle is not adjustable

 

Not all DTCs turn on the CEL - mainly just emissions faults. So, yes: it's possible for a fault to be stored, but the light not to be on. Any time you think you have a problem, pull the codes first.