Help Please

[shaunmelissa]

I have a 1990 b2 and cant seem to figure out whats failing. It runs great when you first start and drive it, after a few miles it starts to miss. It goes away if you shut it off for a few minutes or stop and let it idle. I have put new heads, plugs, wires, timing chain and gears, distributor and coil. Any ideas?

 

[igiveup]

Hello

First did you run the codes? Check them first and report back with your findings.

igiveup

 

[IMenriched]

MAY want to check out the ignition module...(aka, TFI) they act like that after engine is warmed up. other thing can too...but start there.

 

[shaunmelissa]

i came up with codes 41,95.

 

[gbadgley]

41 is Exaust gas sensor
95 is Fuel pump circuit open - EEC processor to motor ground.

 

[shaunmelissa]

well i found today that the filler neck between the gas cap and the tank was dry rotted and had a huge tear in it, could this cause the 95 code?

 

[grnrngr]

I doubt that the torn rubber piece would give you that 95 error, but I'd imagine every time you fill up, the smell of raw gas would be annoying...Had that happen to an old Wagoneer I had, gas pump jockey thought it didn't go in right, split my rubber by jamming the nozzle thru it and sprayed gas all over the packed full load I had back there, including my clothes, as I was moving from CA to OR. I'd be looking for a bare wire hitting the frame or a bad connection or such...41 could be a bad connection, wire, or sensor..

 

[shaunmelissa]

Ive looked all over it for loose or dirty connections, but i'll keep looking. Thanks for the help because im completely stumped

 

[MAKG]

Your PCM and/or body is ungrounded or undergrounded. This can explain both codes.

gbadgley, I know you're trying to help, but there are ABSOLUTELY NO sensor codes, and labelling them as such doesn't do anyone any favors. A 41 is a "lean code," meaning the PCM read < 0.5V between the HEGO sensor and ground, when it commanded the system rich. It means no more than that, and anything that can cause this to happen (sufficiently) will trip the code. Including things like rich misfires.

 

[Psychopete]

95 I think is related to the fuel pump monitor. Basically it's a wire that runs off the positive that actually runs back to the fuel pump relay so that the PCM can monitor the circuit. Do you have a wiring diagram to reference?

** Edit **
I read this later on, it was difficult to understand. The fuel pump monitor wire is connected to the positive fuel pump wire that's from the fuel pump relay. The wire it's monitoring is the actual power wire to the fuel pump.
** Edit **

When you turn your key, can you hear the pump cycle twice? (You might have to have some listen near the tank)

Has the truck repeated this problem while it's in park? You might be able to determine if it's a fuel delivery problem with a fuel pressure gauge if you can get it to act up while it's not moving. You could probably do a similar test with an analog volt meter, maybe even wire something that you can monitor with in the cab - the voltage back at the fuel pump to see if it's dropping off.

The monitor could be affected by the intertia switch - it could be intermittently breaking the connection for some odd reason, but it's not likely.

41 is probably caused by the misfires.

Pete

 

[shaunmelissa]

I will check th grounds and add more grounds to see if it clears up the problem. I check the fuel pump with a pressure guage. I taped it to the window and drove it until it started missing and the pressure didnt drop at all.