1988 7MGE Misfire - Stumped!

[excaliburdj]

Morning, all!

Back in October, I purchased a stock n/a 1988 Supra from a guy at work. The engine was missing badly and had a LOT of white smoke coming out the exhaust. Doing a Google search led me here, where a BHG was diagnosed fairly quickly.

I got lucky in the fact that this car was not his daily driver - he had only put about 20 miles on it since the symptoms started, so I drove it home (slowly) and noticed no overheating or weird gauge behavior, just the miss and the white smoke.

I checked the oil and it wasn't milky, and there was no oil in the coolant, just plumes of white smoke coming out, so everything appeared to be in good shape.

I tore it apart to do the head gasket job. Inspected everything - valves, block, head, etc. Couldn't see any cracks, bending, deformities, etc., so I cleaned it up and installed the new HG. New gaskets from HG on up.

While doing all this, I also replaced:

• Spark plugs (the wires looked OK, so I reused them. He said they were new)
• Distributor cap (the contacts looked a little worn - not bad, but I figured I'd replace it anyway)
• New rotor
• Ignition coil
• Fuel Filter

So I get the car back together, fire it up, and from time to time (more often than not, actually) it misfires through the whole RPM range. It has terrible loss of power when this happens, but other times the stars align correctly and the car runs just fine for an extended period of time.

I talked to the guy at the local parts store, and he seemed to think it might be a dirty fuel system component or water in the tank (because the car sat all winter) so I filled it up with fresh gas and put a can of Sea Foam through it. I've run through about 1/4 of that tank of gas and it isn't getting much better.

I jumped the computer to look for codes, and it isn't throwing any at this point, so I'm completely stumped as to what could be the problem. Sometimes it runs fine, sometimes it doesn't.

Advice on what this could be? Injector? Fuel pump? ICM? Sensor somewhere?

I'm completely stumped.