-red97rum-
20+ Year Contributor
- 1,099
- 44
- Aug 29, 2002
-
Upland,
California
Hoping this is a simple short somewhere, but this one is kicking my ass the past couple days. Here's a little background on the issue.
I've been noticing lately when I shift my car into 2nd gear, the engine will cut out, mpi clicks and the check engine light/boost gauge reset. Now my car was a 5 speed that I swapped over to auto. I didn't swap over any of the auto wiring harness and have the transmission wired up to shift manually with a ratchet shifter. So all the wiring is done on the transmission itself - between the gear selector and the solenoid wires with one wire providing the gear selector unit on the trans 12v. I just got the car back together a couple weeks ago and everything seems to be working fine. It's just that every now and then, lets say 2 out of five 1-2 shifts, this phenomenon will occur.
Things I've done so far:
Checked the ground strap for the transmission, all seems good. I have one ground on a bell housing near the starter and another on the front of the transmission that bolts to the frame rail.
Had a friend ratchet from 1st to 2nd while I observed the cable's movement. The cable hardly moves at all and the part of the harness it touches is secured with zipties and new wire loom installed over it. It can't be that.
So then I start thinking it's ecu related. The reason I was thinking that would be the case was because I had been running a 90 ecu (pins 6 & 14 swapped) and an ISC short blew apart one of the drivers on the board. Since I had my original '92 ecu sitting in the box from ecmlink, with new fresh caps and socket job, I swapped pins 6 & 14 back to their original configuration and threw it in. I'm having the same problem.
Next thing I did was pull the manumatic harness I made, cut off all the crimp spade connectors, solder/heat shrunk each one and then tape it up nice and secure. Same problem.
So last night I was checking the ecu harness plugs to see if any wires were damaged or exposed and somehow shorting... As far as I can tell, everything looks to be in fine working condition.
Next, I eliminated the shifter and clicked the transmission's gear selector between 1st and 2nd from under the hood with a friend watching the check engine light. Viola! It did it again!! Ok, now I know it has to do with the transmission harness/solenoids. But what's getting me, is I'm not sure how it's causing the ecu to lose power? I have an aftermarket fused distro block in the engine bay, due to relocating my battery to the trunk, which is where the transmission get's it's 12v to operate the solenoids. This 12v feed was tapped into the same lug as the MPI fuse, which makes sense if the transmission harness was shorting out inside the gear selector unit, the sudden blip to that circuit could cause this problem. So I moved the 12v feed to the trans over to the fused location that my cooling fans run from and I'm still able to reproduce the problem.
If a 12v source, any for that matter, temporarily shorts out, is that going to cause the ECU to lose power and reboot?
Next, I'm probably going to start investigating the wiring between that 12v source and the gear selector unit, maybe the insulation for that wire has cracked inside the harness cover and it's causing it to short out.
Any ideas or suggestions on what to check next would be appreciated. I do have a spare auto trans with the gear selector and trans harness, so depending on how much work it is to pull it off, I may just try swapping out the entire unit. If that fixes the problem, then I'll go through the wiring on the original gear selector on my bench rather than bending over the damn car. Thanks for reading my novel.
--Dustin
I've been noticing lately when I shift my car into 2nd gear, the engine will cut out, mpi clicks and the check engine light/boost gauge reset. Now my car was a 5 speed that I swapped over to auto. I didn't swap over any of the auto wiring harness and have the transmission wired up to shift manually with a ratchet shifter. So all the wiring is done on the transmission itself - between the gear selector and the solenoid wires with one wire providing the gear selector unit on the trans 12v. I just got the car back together a couple weeks ago and everything seems to be working fine. It's just that every now and then, lets say 2 out of five 1-2 shifts, this phenomenon will occur.
Things I've done so far:
Checked the ground strap for the transmission, all seems good. I have one ground on a bell housing near the starter and another on the front of the transmission that bolts to the frame rail.
Had a friend ratchet from 1st to 2nd while I observed the cable's movement. The cable hardly moves at all and the part of the harness it touches is secured with zipties and new wire loom installed over it. It can't be that.
So then I start thinking it's ecu related. The reason I was thinking that would be the case was because I had been running a 90 ecu (pins 6 & 14 swapped) and an ISC short blew apart one of the drivers on the board. Since I had my original '92 ecu sitting in the box from ecmlink, with new fresh caps and socket job, I swapped pins 6 & 14 back to their original configuration and threw it in. I'm having the same problem.
Next thing I did was pull the manumatic harness I made, cut off all the crimp spade connectors, solder/heat shrunk each one and then tape it up nice and secure. Same problem.
So last night I was checking the ecu harness plugs to see if any wires were damaged or exposed and somehow shorting... As far as I can tell, everything looks to be in fine working condition.
Next, I eliminated the shifter and clicked the transmission's gear selector between 1st and 2nd from under the hood with a friend watching the check engine light. Viola! It did it again!! Ok, now I know it has to do with the transmission harness/solenoids. But what's getting me, is I'm not sure how it's causing the ecu to lose power? I have an aftermarket fused distro block in the engine bay, due to relocating my battery to the trunk, which is where the transmission get's it's 12v to operate the solenoids. This 12v feed was tapped into the same lug as the MPI fuse, which makes sense if the transmission harness was shorting out inside the gear selector unit, the sudden blip to that circuit could cause this problem. So I moved the 12v feed to the trans over to the fused location that my cooling fans run from and I'm still able to reproduce the problem.
If a 12v source, any for that matter, temporarily shorts out, is that going to cause the ECU to lose power and reboot?
Next, I'm probably going to start investigating the wiring between that 12v source and the gear selector unit, maybe the insulation for that wire has cracked inside the harness cover and it's causing it to short out.
Any ideas or suggestions on what to check next would be appreciated. I do have a spare auto trans with the gear selector and trans harness, so depending on how much work it is to pull it off, I may just try swapping out the entire unit. If that fixes the problem, then I'll go through the wiring on the original gear selector on my bench rather than bending over the damn car. Thanks for reading my novel.
--Dustin
