I have an 89 f150 302 with and automatic tranny. Beginning of the nice weather I started taking my truck out from sitting over winter and today discovered the EEC/computer isn't noticing any changes in replacement parts I had put on it. It began with a weird idle so I went through the process of elemination and did new IAC,TPS,MAP,o2, PCV and fully cleaned the upper plenum and EGR passages as well as new upper gaskets and all. Today when trying to pull codes the computer would only say it wasnt noticing WOT and idle RPM. I dont remember exact codes but a guy I know used his high end computer hand held to do the KOER test and he claimed the computer isnt responding to no changes wether we unplugged the TPS leads or IAC leads. He is a mechanic for the local Chevy dealership but he knows a lot about fords and his diagnosis was a new EEC/computer.

My question is what or how exactly do you identify what computer to get. Say I was to go the my local junkyard and pull computers what would I look for? Door jam calibration numbers? Match up numbers on my EEC to another similar truck. I haven't pulled my computer yet so I am not aware if there are numbers listed on the unit itself. And if there are would all similar 89 f150's with a 302 and AOD have matching numbers?

 

I have not hear of any computers on Ford trucks from our era failing like that.
That is not their normal MO of failing.

I would think your computer is still a good one.
Sounds more like bad wires, plugs or parts or the way it was tested.

Try putting all of the old parts back on as they are more than likely better than the new ones if you got them from an auto parts store.

Then run the self-test without the hand held device.
Then if they fail the electrical test (KOEO) then replace the part or check the wiring to get by the electrical test before trying the engine running test.
Also clear your codes by grounding the STI wire, turn on the key and then take the ground away from the STI wire when the MIL starts to flash.

If you do not know how to run a self-test click on the URL below:
Fuel Injection Technical Library » How To Run a Self-Test

If and when you need a computer yes the drawing number should be on the computer.
For a replacement at a junk yard get one from a truck about your same year with the same size engine and type of transmission.

 

It runs the same with or without old parts. All my replacement parts are motorcraft as well.

 

How does it run?

You need to run the electrical test (KOEO), then replace the part or check the wiring and get it by the electrical test before trying the engine running test

I would not trust the high end computer hand held. Use a paper clip to check out the electrical wiring with the KOEO self-test. You could also use the Equus 3145 Ford Digital Code Reader that cost about $30.00 at O'Reilly auto parts or on line at Amazon. Image below.
We have found that most mechanics at Ford dealerships know very little about out era (1985-1995) Ford trucks. They know newer trucks but not ours. If you are going to own a truck from our era you will need to know how to test and work on it yourself. The members on this forum will help you all we can.

Out era computer are very well made and when they do go out it is either the caps inside have leaked out or someone has washed the engine and got water down on the computer plug. Then most of the time you will smell smoke in the cab after washing the engine.
The way they go out is the engine will not run most of the time and the fuel pumps will run all the time the key is on. Sometimes you will not get spark until you unplug the computer other times it will start on starting fluid but not run on gas (no injector action).


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I have the exact reader from innova. When I do koeo it only throws the code for open pressuure switch circuit for the power steering. I did the sag swap and had a hose made and left the pressure switch connector open. That is the only code. Whaat it does is either warm or cold and going frrom drive into park it will idle at 1500rpm and go down to 800rpm and shoot right back up to 1500speed and keep loping like that. It also has a mis at idle.

 

Are you saying the computer gave no codes during KOER self-test with the IAC & TPS unplugged?

By the way the RPM information comes from the PIP sensor in the distributor.
If he did not read RPM information with it running you may have an open wire between the TFI module plug and the computer plug.

 

Yes during koer no codes with them unplugged it only said it wasn't seeing wot even when we fully wrapped the engine. So yes didn't read high rpm with it running

 

During KOEO electrical self-test did they have codes with them unhooked?
You did see any other codes other than the PS code during the KOEO & another 11 for CM when you did the KOEO test?

I we have had bad computers that would not do the self-test and give any codes but you say you are seeing the PS code during the KOEO electrical test.

 

Thanks for the reply! You are pretty techincal lol thanks for the help

I did not try unhooking either TPS or IAC during KOEO. I only got a code 52 during KOEO followed by an 11 and thats it. Whats a CM? The reason we thought new computer was because it was not responding to any fixes or inputs from the big data link during KOER. Why would it keep saying its not seeing high rpm?

 

KOER had codes 411 and 412

 

The 11 above after 52 during the KOEO test is saying that the CM has no codes stored in it.

CM=Computer memory.
The CM stores trouble codes when you are on the road driving and saves them so you know what went wrong later. That is why you do not unhook the battery as you will lose what is in CM. The CM codes are very helpful in finding what is wrong.

 

Oh makes perfect sense. I do not have any driveability problems other than my tires rub if I turn to sharp lol. Its only an idle mis issue and even more so when putting the truck into park after being in gear it fluctuates.

 

Three digit codes are very rare for a 1989 truck unless you have a E4OD transmission in it.

However:
Service Code 412 indicates that during Engine Running Self-Test, engine rpm could not be controlled within the Self-Test upper limit band.
Possible causes:
-- Open or shorted circuit
-- Throttle linkage binding
-- Improper idle airflow set
-- Throttle body/ISC solenoid contamination
-- Items external to Idle Speed Control system that could affect engine rpm.
-- Damaged ISC solenoid
-- Damaged processor

Service Code 411 indicates that during Engine Running Self-Test, engine rpm could not be controlled within the Self-Test lower limit band.
Possible causes:
-- Improper idle air flow set.
-- Vacuum leaks.
-- Throttle linkage binding.
-- Throttle plates open.
-- Improper ignition timing (TFI vehicles only).
-- Throttle body/ISC solenoid contamination.
-- ISC circuit short to ground.
-- Damaged ISC solenoid.

 

Ahh maybe his data link is not fit for my truck. I will do a KOER test tomorrow with my hand held innova and post results.

 

Some updates today.. I busted out my innova code reader and put fresh batteries in it. I did a KOEO test and got the following codes;

21- cooling temp sensor out of ranger or ECT out of range

24- Intake air charge temprature sensor out of range

I have never replaced neither of those sensors nor do I know where those are at. Any advice/help would be great. I browsed through my haynes manual and I couldnt find an ECT or ACT in the manual anywhere to specify where they are located.

Other than that Continuous Memory checked out fine with a pass code 11.