Intermitently misfiring, gas in exhaust.

[geospine]

1992 Mazda B2200 Manual 2.2 liter EFI with 212k miles!
I know it's not a Benz, but I need to haul the trash with something, right?

Engine intermittently misfires on one or more cylinders. Gas leaks out exhaust with grey sludge. Starts easy idles rough then recovers. Had plenty of power for a while and has progressively gotten persistently rougher. Bluish white smoke when warm, probably due to gas in exhaust.

Recently replaced plugs, wires, distributor cap and rotor, fuel filter, air filter and pcv valve(due to failure).

All plugs are firing and in the proper order. Compression is even 90psi across all 4 cylinders. Oil and coolant are clean.

I am thinking possibly o2 sensors? Does anybody know what the voltage readings should be?

What else can I test? Could it be as simple as a faulty fuel injector? Or could it be a faulty ECU causing problems with the injection/ignition sequencing? I read these are prone to failure and are difficult to troubleshoot.

I have been working on this one for a week with no progress now and any input is welcome.

[TJ 450]

It could be any of those things as you've said, but I would pull the spark plugs and inspect the nose of the insulator/electrodes and report their condition first. It is probably an intermittent no spark issue.

Tim

[geospine]

Thanks Tim,

The plugs look fine, still almost new, one was slightly yellowish and wet with gas.

I installed a new distributor and rotor last night then tested with an in-line spark detector that showed spark going to all plugs.

It looks like my next step is to tear into the FI system...

[TJ 450]

Yellowish and wet with gas... I'm thinking that plug isn't firing. If you have a distributor ignition system, I'd check the lead. Otherwise it might be a coil pack.

Tim

[Big_Richard]

.

[geospine]

Thanks for the input guys,
There were two error codes before removing the ECU, one didn't register on any lists, the other was for the ECU itself (and possibly the failure). After examining the ECU (which had some slight discoloration but no obviously failed components) and replacing it, all codes have cleared.

I will try to find some time to dig into it some more this weekend.