Since the MAF conversion, I have had cold start issues: rolling idle and stalling. I have a continuous memory code 15 for loss of keep alive memory. After a few minutes it will eventually relearn and the idle will settle in. If I try to drive too soon the truck will bog down and stumble. Once it “relearns” the truck actually runs pretty strong. I can shut off the truck after driving, fire it up and everything will be fine depending on how long the truck had been sitting.


Left pins got to MAF sensor. Right go to injectors.

The fuel injectors have two pins but three wires for each injector. Would someone know how to check the overlay harness circuit board to see if there is something wrong with it? It was a non H.O. harness that someone else had changed to an H.O. firing order. I saw on here somewhere that all that was needed to do that is to swap a couple wires? I wondering if it was done correctly i.e. what pins should be where on the circuit board? Do the numbers on the board match the pin number for the 60 pin connector?

This is on my ‘89 F-150 302. The conversion was done because SD couldn’t cope with the GT-40 heads and Comp 35-349-8 cam. As a side note my mileage has actually gone down a couple mpg since these changes and it smells like it runs a tad rich.

 

That means your PCM is starting from scratch every time it is started, no tuning is retained. The problem is in the main wiring harness somewhere, could be at corroded wire at the PCM relay(I had that with my '90) There are 2 Orange/black wires that come together at the relay, one goes to Pin1 on the PCM(keep alive memory) and he other goes back the the battery via an inline fusable link. Check all of this for problems.

 

Probably going to start at the relay but haven’t had a chance to work on it. The other day it started and almost right away settled in at a steady idle. Not nearly as bad as usual but now it won’t run the KOEO test.

 

I have 12V on the yellow wire at the EEC relay and at the PCM/ECM. I see the orange / black wire at the relay but not at the 60 pin connector. I am going to reinstall the other MAF overlay harness today since it made no difference in how it behaves when sitting overnight. I tried to disconnect the relay from the harness and it won’t let go. Need to run some errands this morning so I’ll get that done before I break something. I’m hoping it is a corrosion issue at the relay. I had a corrosion issue at the relay when I first got the truck. Maybe it has returned.

Edit: I forgot I picked up an Engine/Emission manual (volume H) and that shows pin 1 Keep Alive Memory as a yellow wire for ‘89. I have power through the overlay harness from the 60 pin connector so that is good. The bad part is that doesn’t help explain why the PCM is losing memory.

 

To close this out:

My problem must have been caused by a bad connection. I had been connecting the overlay harness to the computer and then connecting the engine harness. The last thing I tried was connecting the overlay harness to the engine harness and then to the computer. It has been working great for the last three months. No longer does the idle roll and the engine die until it relearns.