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Dave, There are a few things that spring to mind as to what might be the problem.
1988 was some of the first iterations of EEC4 EFI and there was a recall involving 1989 thru 1991 super duty chassis for a collapsed catalytic converter due to the fuel computer running rich. I'd call your local Ford dealer with your VIN number and see if the cat converter recall applies to your rig.
Another possibility is a bad fuel pressure regulator or a bad or failing high pressure fuel pump (if your rig has 2 fuel tanks). None of these will set a code in your fuel computer.
Since the check engine light doesn't come on while you are under load, I really suspect something mechanical rather than electrical. The only exception is a problem with the ignition module. TFI electronic ignition was in use a few years before 1988, but in 1988 it could still have a problem without setting a code. Ditto with an ignition coil overheating (rare, but will cause what you're experiancing). Your rig should be using the epoxy potted ignition coil (square body). If someone installed an oil filled coil (round body) you should scrap it; It can't handle the demand from TFI.
Hope that helps! |