Running Pig Rich

[fatt_owl2.9]

So I guess my truck has been running really rich for quite a while. The smog tech said it's dumping a "ridiculously" high amount of fuel. My truck's been down at a local and well-recommended smog tech/repair place. Owner just called me and said that all engine sensors seem to be working as they should, fuel pressure regulator is good, and none of the injectors are sticking. He says I should replace the ECU, because all the sensors seem to be working right, but the computer continues to dump too much gas.

I always thought it was pretty rare for an ECU to go bad in any car. Another curious thing is when I bought the truck, it came with a spare ECU, which I believe is the original one for the truck. The ECU that has been installed in the truck since I bought it has 'BRONCO' written in sharpie on the case.

I guess I can try plugging that other ECU back in and seeing if it works, then take it back to my smog guy so he can test it, determine it's shooting normal fuel amounts, then check to see if the cats are fouled.

Is there any special process to ECU swapping? Or is it simply a matter of unplug-remove-install-plug back in? If I do end up having to go junkyard ECU searching, will any 2.9/manual trans ECU work, or do I have to have one specifically from an '87 model?

Thanks in advance for any advice

 

[RustedRanger]

I took my 87 to a shop after comingto my wits end trying to find out why it was running rich. The guy tested the fuel pressure and it showed good.....on the way home it started running crappy again. I ran a pressure gauge on it myself and the pressure pegged the gauge. It was the fuel pressure regulator but it only messed up for me while I was driving it. I also had a broken ground wire they didn't find and also a missing fuel vapor solenoid,which they also didn't notice. Someone took the solenoid off and ran the vapor line right into the throttle body. If you need a regulator I found the cheapest one at Rock Auto .com,I think it was $35 and arrived quickly.

 

[disciplerocks]

Try replacing your front O2 and clearing the ecu. After running very rich or lean for awhile the O2 fill fail so replace it and disconnect your negative battery cable for 10 minutes to reset your ecu so it will re learn your fuel trims off the new sensor.

I also second the regulator. They have a tendency to only fail a percentage of the time when they are going bad.