My plugs are fouling out from black soot. Changing plugs and they foul out within a few miles.
SO far changed TPS, fuel filter, air filter, coil, wires, plugs 3 times.
COde check only have one, right bank O2 sensor not switching, but maybe because the plugs were so fouled that nearly raw gas was going through.
Any idea what should I do next? 1992 w 5.8 EFI .

AQUARIES1

 

EGOS (O2 Sensor) controls fuel trim. If the sensor is sending low volts, the PCM will richen the mixture. So the EGOS could be telling the PCM that the mixture is lean when it's really okay, and the injectors are pulsed on more and the mixture gets really rich. If you are using a scanner, look at the sensor page and see if you can monitor the voltage. My guess is faulty wiring to the EGOS or a faulty EGOS.

 

I wouldn't think that a bad O2 sensor would cause those problems that extreme. I'd check the fuel pressure and the fuel pressure regulator first.

 

Oops, didn't see that they were getting fouled out. Didn't read close enough.

 

Getting worse - NEW O2 Sensor, cap & rotor, and of course a new set of plugs. Plugs fouled out within 3 miles, and it's now barely driveable. Used 2 nd gear to get to work.

Can old injectors (105K miles) dothis?

Wayne

 

I doubt that it is the injectors. Have you checked the fuel pressure yet? I'd also test the TPS and the MAP sensor to make sure both of them are in range as well. Have you tried pulling the codes?

 

Code was O2 sensor not switching.

New TPS, ohm range and voltage checked in spec. and was same as old one. Old O2 sensor was coated with carbon same as plugs. Haven't checked fuel pressure but problem started after replacing fuel filter, while working on a hesitation problem. The hesitation mostly went away with a TB gasket.

 

Pull the vacuum line off the fuel pressure regulator, and check for raw gas. The diaphram in them ruptures, dumping raw gas into the intake, making an extremely rich condition which will foul your plugs.....

 

Thanks for the tip on the regulator. Unfortunately the fuel reg checked out Ok. But found the new TPS had broken. The tabs had sheared. Don't know why. There was no binding when I checked the ohms at open throttle and close throttle. Also lowered the exhaust to check for restriction.

This all started when I changed the fuel filter. Plugs began fouling out a few days later. ???

Still frassled more than ever

Aquaries1

 

What about a severe restriction in the air intake system? Could a rag have been left or stuffed somewhere while working on something? Also check on the dirty atr side before it gets to the air filter to see if something got sucked in there.

 

i have a question for natewoz...your gallery said your grille gaurd was custom made.....who made it, and do they sell them?..i have a 95 f-150 and have been looking for a gaurd for a long time..and, what type of suspension lift do u have?.....sorry, i know this dont have nothing to do with the original thread, but i seen his grille gaurd and it caught my eye..thanks

 

Can anyone tell me where the MAP sensor is on a 92 5.8?

AQUARIES1

 

On the firewall, just up and left of the intake manifold as you are looking at it from the front of the truck. It will have a vacuum line and a 3 wire connector attached to it. With the connector plugged in, you should have 2.5V on the blue wire, and ~5V on the orange wire, both with key on, engine off.

 

Thanks