Intermitently misfiring, gas in exhaust.

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?

1992 Manual 2.2 liter EFI with 212k miles!

im not a mazda engine guy...but 90 is kinda low isnt it?

Here are compression specs for a b2200 standard is 173psi minimum is 121psi.This applies to wether efi or carbd no matter same numbers.Also your oil pressure should be 43-57 psi at 3000rpm.90 umm seems way lowwww,I would reavaluate your #s if it really is the above your rings are toast.I am not a engine guru but,axle breaker earl is spot on these little bs eng rebuilds and may better assist you with more ?s in this dept.Ok and these specs are straight out of the manual and are correct.

Thanks for the input guys,

If the rings are shot how would you explain the intermittent power loss and gas being discharged out the exhaust without combustion?

It is possible that I did the compression test wrong, It was a rental tester and my first time doing a compression test. I was just happy that they all came up +-1psi of each other.

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 heard these are prone to failure and are difficult to troubleshoot.

Idk alot about the efi setups.And was tired when I posted so,some oversight.As for checking the injectors yeah I would.The haynes manual has a pretty elaborate explaination and in short injectors should have 6-8 ohms resistance.The manual details checking each injector,for leaks,harness and relay info.I am not sure the 2.2 ecm had issues it is more the 2.6 on my recall.If it is dumping fuel as it is could be one injector or orings leaking.Buy a haynes manual 1972-1993 for about 25 bux.Much easier for good references for the whole truck anyway.

Both of the 2 EFI Mazda engines, the 2.2 and the 2.6, can have ECU issues. There are 2 capacitors on the ECU board that will leak (If it is a factory ECU and the capacitors have not been swapped out) and start etching the traces and other components on the board.
What I would do is disconnect the battery, unplug and remove the ECU, it's located behind the passenger side kick panel, and remove the cover and have a look at the board.
If you have some leakage from those two caps, then it is time to send it to a company like AvPro and have them fix it, or look for another ECU........I would have yours fixed though.

Here is a few pics of a B2600i computer, but the one for the B2200 is very similar.





Here's one that was in my truck when I first bought it.......it worked, but the MPG was not too good. I got lucky and found a good one at our local JY and put it in my truck and I picked up at least 2 MPG on in town driving! This ECU had leaked and the board was hurting!!



The company that "fixed" this one was NOT AvPro by the way! They kinda butchered this I think......







Bottom line........look at your ECU board BEFORE you throw any more money at the truck!
If your not sure of what it looks like......take a few good CAMERA pictures, and post them here for us to look at.

Let us know what you find out.

Thanks for the info and pix Earl,

Before I removed the ECU I was getting error codes 2 and 17. I am not sure what 2 is but I think 17 is ECU failure so you may be on to something.

The black thing with the x on it must be the failed cap. then because there was red goo around it (near the # sign on the board) which I unfortunately scraped off before taking the picture.

Should I also replace the red cap. indicated by the arrow?
How much does AVPro charge for this kind of job?

was your throttle wide open when you were doing the compression test? Were ALL of the spark plugs out? How many engine revolutions passed?

Hmmm, no and no. Being a novice to compression testing, I simply unplugged the FI system, unplugged the coil, removed the foremost plug, installed the tester, turned the engine over four of five times, checked the reading, then moved on to the next plug. I should also note that I neglected to do a valve job before testing. I was just trying to rule out a blown head gasket.

AvPro is going to be around $100.00 or so I would imagine. Your board looks pretty darned good, so you might want to try replacing those 2 caps yourself and see what you've got after that.......one's red, and the other is black.......the silver thing is a transistor I think.

Look closely to make certain that the goo that you scrapped off didn't eat through a trace on the board, and I would clean that area with a small brush dipped in Windex or similar cleaner that will remove any of the acid traces from the failed capacitor.