White smoke, black smoke, rough idle.

'94 Mazda B4000, manual trans, 233k miles.

So driving it home a month ago it started running REAL rough, hesitating, trying to stall, didn't want to idle for more than a few seconds without the RPM dropping so I kept having to tap the accelerator to keep it from stalling while idling. Felt like 2-3 cylinders misfiring.

Black smoke and black fluid (assuming unburnt fuel?) dripping from tailpipe.

Threw in a new ignition coil from the kind chinese manufacturers on eBay. Cleaned & gapped the plugs. They were sooty, as expected. Engine wouldn't even start (I did the wires right!) It cranked and tried to fire and made some funny noises and shook a lot. I put the old one back in and it started that time. Except it still ran rough and gave me black smoke.

Pulled codes, I got the 122-125 for the TPS and also the similar codes for the MAF (out of range / too high / too low).
Replaced fuel filter, cleaned MAF, throttle body, IAC valve (also verified that it works) tested TPS with multimeter (still could be intermittent failure?) Air filter replaced within the last 6 months.

Started it up. Idled alright! Still not *perfect* but was not hesitating, trying to die, etc. No black smoke. But this time was getting white smoke! Not a lot, and I would get some puffs then nothing, puffs then nothing, etc.
Then 3-4 minutes later the white smoke stopped and some black smoke started again, the RPMs dropped, and it stalled.

I checked the oil and coolant. Oil isn't a milky color, coolant isn't frothy or oily.

Maybe my cat got clogged up from all the unburnt fuel from whatever was causing the misfire? Maybe the TPS really is malfunctioning intermittently? Maybe the MAF is ****ed (I couldn't figure out which pins to test b/c they weren't marked but I'll try again tomorrow.) Also there are some feathers and acorns and shit under the intake manifold, maybe something got in and screwed up some fuel injector wires or other wires? But I can't really see or get in there without pulling the manifold off.


Any help would be GREATLY appreciated. I'm almost considering just selling the vehicle for scrap value.

I'm wondering where the O2 code is at. Running like that it should be reporting something.

High and low on two sensors makes me think it's wiring.

Right, I was thinking wiring too, but the MAF wiring isn't routed in the same place as the TPS wiring (which goes under the intake manifold which is where the feathers/acorns/shit is)

I didn't get any O2 codes but it also didn't give me any engine running codes, which was odd.

I'm also wondering if the cat got clogged up, maybe I'll cut that out and see if I get an improvement.

Think I should take off the intake manifold and check out that wiring? I was hoping not to do that but I guess it couldn't hurt

On the fuel rail is the Fuel Pressure regulator(FPR), it has the 2 fuel lines attached, IN and Return, it also has a vacuum hose attached.
Remove the vacuum hose and check it for fuel or fuel smell, if fuel is found replace FPR.

If the FPR diaphragm starts to leak, raw fuel is sucked into the intake, causing the black smoke and poor operation.

A stuck open injector can cause same type of issue.
There is a routine on all computer control engines called the "Clear Flooded Engine routine".

Turn on key
Push gas pedal to the floor and hold it there
Crank engine
Engine should NOT start, or even fire

With key on and gas pedal to the floor the computer reads above 4.5volts from TPS(throttle position sensor), this starts the routine, which shuts off fuel injector pulses, but leaves spark on.
So there should be no fuel going to engine, so no starting or firing.

If engine fires then you have fuel leaking in from somewhere, if FPR isn't leaking then a fuel injector is.

If you release the gas pedal while cranking engine will start normally, computer will restart injector pulses when TPS voltage drops below 4.5volts.

If you think it is a leaking injector you can usually ID which one by using the above test routine BUT, unplug the coil first.
Use the above routine then pull one spark plug at a time, the wet one has the leaking injector.

Clogged exhaust would usually first show up as limited RPMs at highway speeds, from pressure building up at exhaust ports.
Same symptom of fuel filter getting dirty.
But neither would have black smoke involved