running rough!!!

[redthunder]

I have a 94 Ex Eddie Bauer that is running extremely rough. Pulled a plug it showed very rich. Took it to Autozone, they read codes of 542 and 761(?). Changed fuel pump relay, not it. Not sure what the cause of the Fuel Pump Secondary Circuit failure , PCM to ground would be. Took the vehicle to a Tech. Hooked it up to his computer, got erratic O2 readings. Changed O2 sensors, it ran a little better. Hooked it up to computer again, seeing no voltage change at the MAF sensor. Changed MAF. Running a little better. Hooked the computer back up, got codes of 177 (HEGO too lean now)and 542 (still don't know what that is). Tech decided to disconnect left O2 sensor. Hooked up a dummy sensor. Started vehicle O2 readings on left side very erratic (just like when the real O2 sensor was in). Thinking the computer is going. Could this be the problem?
FYI - As the Tech was bringing up the codes, they were coming VERY slow (one every minute or two). Also, starting from a stop, applying 1/4 throttle, this thing is a dog, but, at 2400 RPM it wants to take off w/o applying anymore throttle. One more thing, just pulled a plug from each side, does look a little lean now, still running like CRAP!!!

Sorry so long and Thanks in advance

 

[88vert]

Have you checked the Fuel pressure regulator?Does it start up real easy?

 

[redthunder]

yea I forgot to mention that, it was 31 lbs. It didn't bleed off after shuting the engine off either.

 

[88vert]

It just sounds like a fuel problem.Does it run the same with a full tank of gas?when is the last time you changed the fuel filter?

 

[redthunder]

UPDATE.......

changed the FPR on Friday 8/2. Took the Neg. battery cable off over night. Ran it the next day, and, it ran
like a new vehicle again. Until, about 10 miles later got a CEL. In that 10 miles, I went and filled up the tank. I haven't been able to get the CEL's checked yet. Occasionally the thing will feel like a dog @ low RPM, and, sometimes it runs great.
Has anybody got any clues as to the 542 code yet?

Still

 

[88vert]

you could have messed up the o2 sensor with a bad FPR

 

[Rhett]

code 542 = fuel pump circuit open, PCM to motor.

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btw, my truck threw a code 177 (O2 sensor rich) just this weekend. And it ran rough when the CEL came on just like yours. It only did it with low fuel in the tank though...if i fill up it won't do it. I guess it's time to get FPR checked; time for new o2s.

 

[redthunder]

UPDATE #2....

Thanks to everyone on this board for helping with my problem, even if you didn't respond. I found other threads that helped in this journey.

I finally broke down last week and bought a new computer (per my tech's advice). Installed it on Tues. Ran it around for 20-30 miles, runs great. But, the true test was when the wife used it for work. She is a rural carrier for the USPS. Ran great all day long (715 stops). Took it to my Tech., he hooked it up to his machine, and, holy ****, no codes, and the voltages are all perfect.
.........now I gotta go change brakes again

 

[410Fortune]

Damn I missed it....

I had a similar problem. I was going to recommend swapping out computers with a known good unit.

Sometimes when the stupid thing is giving you codes, you check all the codes and know that in fact all the sensors, etc are working the problem can be the computer itself. Now shelling out $300 to Ford for a remand computer is not always a good idea unless you know for sure it's the problem so if you look around to local used auto parts places or junk yards you can find them cheap!!!

I got my replacement for $60, works perfectly........

If something is telling you computer (instinct, slow codes, know 02's are good and it tells you 02's) try finding a buddy with the same truck (computer calibration code) and swapping the brainbox out to see if the problem goes away before dropping a ton of $$$ on a new computer.

Now I have a ???? for you. Did you do or have any work doneto the truck that might have caused this computer to go bad, any voltage spikes from welding or hooking up aftermarket accessories? anything? (just curious)

 

[redthunder]

There was no other work done to it except changing the oil at the time.
This all started with the X "lunging" at stop lights. Then it was running real rich.
And that started the dumping of the money.