This thing is driving me nuts. It started 2 weeks ago after driving it in the rain, then it sat for 2 days. It was hard to start and then backfired on me, then was fine. Once it dried up it ran fine for a week.
Then same thing, drive in the rain, sit for 2 days and hard to start again.
Then it started doing it all the time. At first after starting it would cough and sputter at about 200 RPM for 5 seconds then die, then start up fine.
But it was running pig rich and fouling plugs.
After 5 mins of idling, the long-term fuel trims were already at 108, so the PCM knows its running rich and trying to compensate.
Now when I try to start it, it tries to idle but its actually coughing back out the intake.

-Compression is 200 across the board.
-Fuel pressure is good and doesn't leak down. Also checked the injectors and FPR for leakage and nothing.
-All sensors scanned are reading within limits.
-Had opti off and it looks mint, not a hint of moisture or rust inside. Cap and rotor were a little worn but cleaned right up and didn't change a thing.
-Unhooked MAF and nothing changed.
-Plugs did nothing, wires all look in good shape, only 2 years old.

Its a 97, bolt on car, stock injectors.

Anybody have any ideas, it is greatly appreciated!

 

Have you checked the opti harness? If the harness is corrorded, it could cause these problems

 

It looks mint.

 

Now it won't even really start. It just sputters and coughs at about 100 rpm and coughs back out the intake with each rotation.

 

o2 sensors? you ever done anything to the rocker arms?

 

O2's are a year and a half old and reading fine. Besides it does it right from cold start.
Never touched the rockers, why?

 

Anybody have any ideas?
There has to be something I'm not thinking of.

 

I'll venture a guess to say ignition related and probably a global issue. By that I mean not individual plugs or wire but rather something that effects all the plugs such as coil wire, coil or ICM.

check the spark quality at a few random easily accessable plugs. If it's not what it should be, try a new coil and coil wire. Wouldn't hurt to look at the coil and wire at night while it's running either.