93 running pig rich black plugs

Mstng93SSP · Aug 28, 2023

So, my 93 with a 331 and 24 lb injectors suddenly began running really rich. I checked fuel pressure and it was a little high (42 with vac off), but no fuel in the vacuum line to the regulator so regulator seems ok. The plugs are all fouled, some worse than others. 1 is not bad, 2,3,4 all black, 5 and 7 not bad 6 and 8 black. I swapped ecu (as I have spares) no change. I have tons of parts so I literally could swap every sensor, and injectors if needed. Where should I start? I can not run car to get running codes, engine off I get code 34.

Car has a new maf calibrated to the 24s. Car ran fine and issue ame on suddenly.

TOOLOW91 · Aug 29, 2023

What mass air sensor ?

Mstng93SSP · Aug 29, 2023

Pro-M and it is new. The car was running fine with this meter before the issue started.

TOOLOW91 · Aug 29, 2023

Mstng93SSP said:
Pro-M and it is new. The car was running fine with this meter before the issue started.

I’m wondering if for some reason though although unlikely the meter is going away .

Check ect sensor as well

Mstng93SSP · Aug 29, 2023

I have LOTS of stuff, a different mass air meter isn't one of them unfortunately.

Mstng93SSP · Aug 29, 2023

I have a known good ect sensor I will swap in

Mustang5L5 · Aug 29, 2023

ECT would be my first sensor swap. Also check for vac leaks, although that would need to be a fairly large one for you to go that rich.

AeroCoupe · Aug 29, 2023

Long shot but make sure your O2 sensor harness is plugged into the main EEC harness. I had this happen once long ago where the connectors looked plugged into one another but they were not. Was driving the car back home from visiting family and it all of a sudden started running pig rich. I went over everything and by dumb luck moved the harness at that point and the O2 sensor harness fell out of the EEC harness connector.

Mstng93SSP · Aug 29, 2023

I will check that out. Thanks

Mstng93SSP · Aug 29, 2023

Based on the condition of my plugs I would imagine my o2 sensors are shot. I will replace those as well.

AeroCoupe · Aug 29, 2023

Have you tried just pulling the codes cold? At least it may give you some idea of the stored codes which might help diagnose what's going on.

Mstng93SSP · Aug 29, 2023

I did. Only got code 34.

rednotch · Sep 2, 2023

Mstng93SSP said:
Based on the condition of my plugs I would imagine my o2 sensors are shot. I will replace those as well.

You can generally clean up the old style o2 these cars use with a torch if the still good and just caked up but generally they will throw a code when the readings are that far off. The code 34 could be the egr not fully seating, and with how caked those plugs, are pulling it isn't a bad idea if the system is still functional. High chance its pretty caked up also and stuck which can wreak havoc on idle and the computer trying to compensate for it.

Mstng93SSP · Sep 2, 2023

I have a few clean EGR valves so I will just swap it. Thanks

chilsam · Sep 3, 2023

fuel pressure reg leaking ?...I had a 93 Bronco with a 351, and thats what it was. Pull the vacuum line off of it if its bad the line will be full of fuel shooting into the intake....GOOD LUCK !

Mstng93SSP · Sep 3, 2023

FPR was checked, no leaking. Fuel pressure seems fine as well.

Sunshine Guy · Sep 3, 2023

Try to determine whether the rich condition is only in closed loop operation. If it runs pig rich during "light" or "normal" driving but does not fog out black (fuel) smoke under full throttle, hard acceleration, then the problem is in the closed loop control system. If that is the case, based on what else you've checked I would suspect a failure in the new mass air meter electronics or failed oxygen sensor(s).

Mstng93SSP · Sep 4, 2023

I cleaned the maf and changed the coolant temp sensor and spark plugs. Car back running normal now. I will update if the issue happens again. I still need to check the fuel tank vent as I think there is an issue there. When filling the tank the gas pump clicks off unless I go EXTREMELY slow when pumping gas.

Monkeybutt2000 · Sep 4, 2023

Mstng93SSP said:
I cleaned the maf and changed rhe coolant temp sensor and spark plugs. Car back running normal now. I will update if the issue happens again. I still need to check the fuel tank vent as I think there is an issue there. When filling the tank the gas pump clicks off unless I go EXTREMELY slow when pumping gas.

Did you ohm test the old ect? I had this problem with a new ect,was bad outta' the box. Put old one back in (after ohm test) all is well.

93 running pig rich black plugs

Mstng93SSP

You have a nice rear end there Dave.

TOOLOW91

If you're the village idiot what's that make me?

Mstng93SSP

You have a nice rear end there Dave.

TOOLOW91

If you're the village idiot what's that make me?

Mstng93SSP

You have a nice rear end there Dave.

Mstng93SSP

You have a nice rear end there Dave.

Mustang5L5

That is…until I whipped out my Bissell

AeroCoupe

lube between the nut and the face. I know my lubes

Mstng93SSP

You have a nice rear end there Dave.

Mstng93SSP

You have a nice rear end there Dave.

AeroCoupe

lube between the nut and the face. I know my lubes

Mstng93SSP

You have a nice rear end there Dave.

rednotch

I'd like to remain having one chocolate starfish

Mstng93SSP

You have a nice rear end there Dave.

chilsam

Member

Mstng93SSP

You have a nice rear end there Dave.

Sunshine Guy

New Member

Mstng93SSP

You have a nice rear end there Dave.

Monkeybutt2000

Mustang Master

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93 running pig rich black plugs

You have a nice rear end there Dave.

If you're the village idiot what's that make me?

You have a nice rear end there Dave.

If you're the village idiot what's that make me?

You have a nice rear end there Dave.

You have a nice rear end there Dave.

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

You have a nice rear end there Dave.

You have a nice rear end there Dave.

lube between the nut and the face. I know my lubes

You have a nice rear end there Dave.

I'd like to remain having one chocolate starfish

You have a nice rear end there Dave.

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You have a nice rear end there Dave.

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You have a nice rear end there Dave.

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