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My 1985 F-150 300 CID started surging while at idle. I decided to check for codes using a Sunpro Code Scanner. The scanner was crazy. The light never went out, just flickered. The system never went through its checks like it did other times. The light never stopped flickering. I also checked the system using the volt meter method to verify what I saw with the scanner. Same thing, needle wavered some, but never would swing like it should and never stopped. Is this an indication that the computer needs replaced.
Update on No Code: Got the truck on the road today. It starts, seems to run OK, but has a miss on acceleration and intermittent when at cruising speed. Hooked up the code scanner again. Computer does not run the self check where you normally hear things being activated. Scanner light just stays on.
I worked through Pinpoint Test Q from the Emissions Diagnostics book and the results indicate replace the processor. I still want to check a couple other things out that I got off the Internet before replacing the computer.
I replaced the computer and still cannot get any codes. Nothing at all. Light stays lit on the Sunpro Scanner. Anyone had problems where you could not get codes from the computer? The truck will run, but not well.
Go to www.fordfuelinjection.com, and try the testlight or meter method for getting the codes. If your system is EECIV, even though it's not fuel injected, it should still work the same way.
I finally gave up and sent it to a garage. The culprit was a bad splice. The mechanic said it was a splice from a wire on the hot side of the starter solenoid to the computer. The wire had 12 volts until the computer put a load on the wire, then it went to 7 volts. Truck now runs great.