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I recently purchased an '86 Ford F150 with the fuel injected V8 5.0 liter. This morning I installed new plugs, spark plug wires and an air filter. The old plugs were completely rusted out. Now the truck is running really rough. Seems like the timing is off or something. When I accelerate it sputters along and sounds horrible. As I did the spark plug wires I made sure to do them one at a time, tracing each one back to the distributor cap, which by the way seemed a bit loose. I also checked to make sure the spark plugs were gapped correctly.
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Look it up here, and recheck the plug wire routing. Also, make sure all the plugs are fully screwed in - not crossthreaded. Spray some soapy water (Windex) on the plugs while the engine is cool & running, and watch for bubbles. If you do it near dark, you can also watch for leaking sparks.
Since this is an EFI truck, you may just need to reset the ECU - the existing data will have been skewed by the dead plugs, etc... Unhook the negative battery terminal, for about an hour, and then start the engine and let it idle until it reaches operating temperature. That should reset the ECU to the factory defaults, and allow it to adjust to the new plugs much quicker.
It only takes 5-10 minutes for the KAM to be erased when the EEC loses power, but you shouldn't let it relearn at idle. You should drive it ~10 miles so it learns the real parameters. Read this.
Thanks for the correction - I usually just say an hour, since various car/truck applications have different combinations of inline caps, etc., to keep from wiping the ECU during transient power losses. An hour will usually wipe anything.
Where in the 'read this' article was reset procedure discussed? Did I miss something?
You're right - it wasn't there. I've read documentation on it so much that I assumed I had included it in that thread, but I've added more info off the CD now.
Two of the wires were crossed on the distributor. While I was checking that out I removed the negative battery cable for an hour and the truck runs great. Thank you very much Steve and Gavin.
Originally posted by steve83 It only takes 5-10 minutes for the KAM to be erased when the EEC loses power, but you shouldn't let it relearn at idle. You should drive it ~10 miles so it learns the real parameters. Read this.
When you disconnect the negative battery cable, if you short it
to the positive battery terminal, it will discharge the de-coupling
capacitors in the PCM for the KAM immediately. Because the
KAM draws such a small current, it takes awhile for the de-coupling capacitors to discharge.