No spark, wiring issue?

[DSM pHrEaK]

Hello all...new to dsmtuners, have been on gatewaydsm.org for a few years now. This is truly a wonderful site here, very informative. What I've got going on is rather confusing....I will explain...in detail. I recently rebuilt a 6bolt for my 91gvr4 and it's ran great for the first 500 miles...now i have no spark in cylinders 1 or 4...let me explain what makes this different from other "no spark" cases. I had just got back from a trip across town, car ran great, shut it off, got back in ~5min later and noticed she was running rather rough, just out of no where. Checked spark and discovered I was not getting any to cylinders 1 or 4. So I turned to my massive parts collection and started replacing known causes 1 by 1 (all with known working parts). First the ignition coil...nothing changed still no spark, 2nd the transistor module...same thing still no spark, 3rd the cas sensor...you got it...nothing, 4th swapped ecu with spare...still nothing, started to grow frustrated. Got on vfaq and printed off the ecu pinouts and checked the wiring from the transistor module to the ecu...all ohmed out fine...checked from transistor module to coil...fine. Thaught to myself "ok time to check injector pulse" thinking that if i had no spark and no injector pulse i could start tracing back the wiring from the cam sensor to the ecu...and you guessed it...have injector pulse. I honestly don't known what other direction to go here fellas...anyone have any suggestions?

 

[90moneypit]

Try swapping your coil packs with ones known to fire, not just a spare one lying around. It's possible that your spare went bad between the time it was pulled and now. It sounds like everything else electrical has checked out to send the signal TO the coil, it's just not doing what it should. The other options (which I'm guessing you've checked) is fouled plugs or bad plug wires but less likely to burn a pair at the same time. You state that you lost spark on 1 & 4 which are on the same coil which leads me to believe it's another faulty coil or bad connection between harness to coil.

 

[Bender]

If one of your coil packs is sending spark on cylinders 2&3, wire that coil to trigger wire 1 from the ignitor for cylinders 1&4. If it works, it's the coil. If not, the issue is elsewhere.

 

[DSM pHrEaK]

If one of your coil packs is sending spark on cylinders 2&3, wire that coil to trigger wire 1 from the ignitor for cylinders 1&4. If it works, it's the coil. If not, the issue is elsewhere.

How would i wire that exactly? Are you saying take the wire from the transistor that controls 1&4 and wire it to the coil for 2&3?

 

[kilo4]

Wow!!! I had the same EXACT problem. It took
me 3 months to fix. I've replace everything including ECU. I was desperate and frustrated. The solution was very simple "loose pin 54" on ECU. After a few beers my freind and I started the car and let it run, huff and puff. We started shaking wires on everything and once we wiggled the ecu wires. It ran smooth and that's how we found pin 54. I hope yours is also simple, good luck.

 

[DSM pHrEaK]

Wow!!! I had the same EXACT problem. It took
me 3 months to fix. I've replace everything including ECU. I was desperate and frustrated. The solution was very simple "loose pin 54" on ECU. After a few beers my freind and I started the car and let it run, huff and puff. We started shaking wires on everything and once we wiggled the ecu wires. It ran smooth and that's how we found pin 54. I hope yours is also simple, good luck.

sweet...yeah i'm going to do some more investigation work tomorrow or day after pending on rain...hopefully something simple like you said. I'll make sure to let everyone know what it was once i track it down.

 

[Bender]

How would i wire that exactly? Are you saying take the wire from the transistor that controls 1&4 and wire it to the coil for 2&3?

Take the coil trigger that comes from 1/4 on the ignitor (and goes to coil 1/4) and wire it to coil 2/3. Basically, take the 3 pin coil pack connector, and switch the 2 trigger wires so coil 1/4 is triggered by the 2/3 circuit, and coil 2/3 is triggered by the 1/4 circuit. See if you lose spark in coils 2/3, but gain them in 1/4. If that is the case, the problem is down stream the coils. If it isn't, then the problem is the coils.

 

[DSM pHrEaK]

Take the coil trigger that comes from 1/4 on the ignitor (and goes to coil 1/4) and wire it to coil 2/3. Basically, take the 3 pin coil pack connector, and switch the 2 trigger wires so coil 1/4 is triggered by the 2/3 circuit, and coil 2/3 is triggered by the 1/4 circuit. See if you lose spark in coils 2/3, but gain them in 1/4. If that is the case, the problem is down stream the coils. If it isn't, then the problem is the coils.

Did this today and of course the outcome wasn't the simple one. I gained spark on 1/4 and lost it on 2/3. I ohm tested the wire going from the ecu to the transistor for 1/4 (pin 54 yellow wire) and the circuit tested fine. This leads me to suspect the transistor is bad but I've swapped it out twice now and it makes no difference.

 

[DSM pHrEaK]

Turned out to be a loose connection somewhere...I just let it run and started moving the main wiring harness around and it corrected itself. I then suspected something to have been shorted or burned so i stripped the tape off the loom and checked all the wires and none of them were bad (covered in oil though...how i do not know). Didn't really figure out what it was but at least its going now

 

[90moneypit]

Yeah, I wish there was an affordable underhood harness for the 90's. Mine is so dry and brittle I expect electrical problems before mechanical ones these days. There's probably a section of your wire that has crystalized so this may be a short honeymoon of happiness before it starts acting up again.