93 running pig rich black plugs

[Mstng93SSP]

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]

What mass air sensor ?

 

[Mstng93SSP]

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

 

[TOOLOW91]

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]

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

 

[Mstng93SSP]

I have a known good ect sensor I will swap in

 

[Mustang5L5]

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]

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]

I will check that out. Thanks

 

[Mstng93SSP]

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

 

[AeroCoupe]

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]

I did. Only got code 34.

 

[rednotch]

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]

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

 

[chilsam]

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]

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

 

[Sunshine Guy]

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]

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]

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.