Hi folks, I'm asking for guidance here on driveability issues with my motorhome.
The chassis is a '92 Chev P30, drivetrain is /454 engine /4L80E trans/ 7060 ECU with the AWUM calpack. (I also have a BAMM that I can use)
This rig has been mostly ok in the five years I've had it, but about a month ago driving on the highway (minding my own business!) it jumped into neutral for a few milliseconds, engine revved, set an MIL and then it came back to normal, did it a few more times in the next five miles till I got it home.
Put my scanner on it, no codes.
Since then I've put all new solenoids in the trans, swapped out the IAC MAP EVRV and TPS with spares, tried a replacement ECU, and haven't found a real solution.
It'll run fine for a little while, but always misbehaves in some way if I drive it very long. I don't trust it on the road now for obvious reasons. It weighs six tons and doesn't have a drivers door. No fun when it dies in traffic.
When it runs badly the symptoms are poor idle control, both high and low, no starts - sometimes there's no fuel being sprayed, other times it goes full dump even before I've cranked it over, a lot of times the scanner won't connect and when it does there's usually no codes, though I once got a whole page of sensor codes. Early on I would pull the ECU and let it cool as it seemed to be getting warm. I finally had to re-crimp the pins I'd had it out so many times.
I have replaced the fuel pump in the past and set pressure, the rig is also completely stock.
It seems that I can get it to act up by wiggling the ECU pigtail wires and I've been trying to narrow it down to which one, or at least what group. Haven't had success with that yet.
The ECU does have power and ground where it should, and I've done pinout checks to all the sensors as much as I could without finding any obvious problems. I've checked the distributor pickup coil - @ 800 ohms, I have had problems with that before, but it seems good now.
I've pulled the underdash harness out through the firewall and gone over it looking for bad splices, checked my grounds, (I also got the GM wiring book - P models diagnosis and wiring diagrams so I'd at least have some information).
But I'm a little stuck at getting this narrowed down.
Any help with troubleshooting techniques and/or common failure knowledge on this would be greatly appreciated.
Thanks
Bob.