1993 Explorer, ECC issue? Sanity check

[sgleisner]

As the title says, I have a 1993 Explorer that has been a nightmare to troubleshoot. I've been chasing this one for around 6 months. It started stumbling and cutting out, mostly when it was cold outside. Thought a tune-up would help, so I went with new plugs, air filter, etc. Still happening. It seemed to just be a lean issue, so I started down that path. Checked engine vacuum (14 lbs at idle, responds correctly to accelleration) Ended up replacing the fuel pump, pressure regulator and fuel filter when the fuel pressure seemed low. That didnt solve it, so went with the rest of the codes. Ended up with a new TPS and MAF. Had the cat flow tested (it was fine). After replacing all that, the codes pointed at lean left side, so I went down that path. Replaced O2 sensors. Nothing worked. Started electrical troubleshooting, and found that it is indeed the left (drivers) side, because of the voltages on the injectors. The supply voltage is fine but the ECC is telling the left side not to push fuel.

Now if I understand it, unplugging the MAF should push the ECC into open loop, where it will rely on the TPS and crankshaft sensor only. I did that, and the ECC is still not sending a signal to the injectors on the drivers side. The only trouble code that keeps resetting now is lean, left side. I'm feeling that the ECC is really confused. I tried disconnecting the battery for 30 minutes to clear any drivability memory, didnt help.

Symptoms are that the engine starts and runs only on the passenger side cylinders. If you run it at high rpm under load for 10 minutes or so, the engine "wakes up" at higher rpms. As soon as the rpms drop it shuts down half the engine and it all starts over.

I dont know enough about ODB-1 to know if the lean code is what the ECC is reading or telling the engine, but it seems to me that in open loop it *should* fire all the injectors.

Am I thinking right? Any ideas? Anyone have something like this ever happen?

Thank you!

 

[sgleisner]

Figured I'd give people an update just in case someone else runs into this. I finally checked the voltages both at all the injectors and the eec, turns out there isnt any voltage on the injectors on the left side of the engine, even at ignition on, engine not running. I checked voltage on the wire that's supposed to supply current (white wire) at the eec and nothing. The injectors on the right side of the engine (tan wire) has voltage. I think its probably the eec after all. I unplugged the battery a hour ago to try to really wipe out the drivability memory, I'll post again after I get results and put the intake back on.

 

[MrShorty]

Before we blame the PCM, let's make sure we understand how this is wired.

You state that you have no voltage to the injectors KOEO. This suggests to me a fault in the wiring between the EEC relay and the injectors rather than a PCM fault. The fuel injectors receive a constant +12 V from the EEC relay, and the PCM acts as a ground side switch. No voltage at all for that bank of injectors suggests to me a broken wire between the EEC relay and the injectors.

 

[sgleisner]

Re: update

I was looking over the wiring diagram, and it shows a red wire from the computer feeding all the injectors, a white wire from the computer feeding the drivers side bank, and a tan wire from the computer feeding the passenger side bank.The voltages (or lack of) at the injectors are the same as I read at the computer itself, behind the passenger side kick panel. If there is an external relay somewhere that would impact just the drivers side injectors, PLEASE do you know where it is? The relay in the relay box under the hood only seems to cover the computer as a whole.

Steve

 

[MrShorty]

I was looking over the wiring diagram, and it shows a red wire from the computer feeding all the injectors,

I guess your wiring diagram doesn't show it all, but this red wire is the main computer power supply. It feeds power to the entire engine management system (PCM, injectors, EVR solenoid, transmission solenoids, fuel pump relay, etc.). That relay you refer to should be the one.

a white wire from the computer feeding the drivers side bank, and a tan wire from the computer feeding the passenger side bank.

These are the "ground" wires from the injectors to the PCM. As noted above, the PCM acts as a "ground side switch." I don't know solid state electronics, so I don't know exactly what that switch looks like inside the PCM.

The voltages (or lack of) at the injectors are the same as I read at the computer itself, behind the passenger side kick panel.

This tells me that there is something wrong with the PCM power supply, between the EEC relay and the PCM/injectors. Maybe the relay itself, but then the one bank of injectors wouldn't fire either.

 

[JReynaxd40]

I have a similar problem my EX is a 94 and it keeps reading left bank lean. Ive torn it down replaced lower and upper intake gaskets as well as the fuel injector orings and the fuel rail gasket. Ive checked all the vaccume lines and they all look good sprayed carb cleaner around the vacume lines and gaskets but no increase in rpm. I checked and all fuel injectors are operational. anybody have any ideas about that? I replaced the o2 sensor on the left bank also with no luck. right after that i noticed a piece of foil stuck inbetween two prongs on the o2 sensor cable think that could be the culprit? the last time i went to pull codes it would give me the koeo but when i went to do the koer it would freeze at the cylinder numbers.

 

[JReynaxd40]

Turns out my problem was a bad 02 sensor. Hope you find out what is goin on with yours.

 

[todd2506]

That post is nearly 2 years old, Im sure its fixed or gone by now;;;

 

[JReynaxd40]

One can only hope haha