91TurboZ
10+ Year Contributor
- 48
- 2
- May 14, 2010
-
York,
Pennsylvania
As the title states, I'm not getting spark on cylinders 1 & 4. I have a 99 GSX with a 6-bolt motor and 1g CAS. I'm using a JMF coil pack bracket due to the intake manifold. The rest of my mods are in my profile..
Anyway, the background. I drove the car into work Wednesday morning and it was running great until I drove over the speed bump at the plant's entrance. I went over it slowly and there were no clearance issues or scraping. As soon as I got over it, the car started running poorly. I got out and started pulling plug wires and found that cylinder 1 & 4 were not sparking.
I've done a good deal of searching and based on previous results I've tried the following:
Replaced coil pack for cylinder 1 and 4 with a new Auto Zone part. This had no effect. I also swapped plug wires around with no effect.
Replace power transistor with a used one.The car s fired up great and was running on all 4 cylinders. I got out to check a few things in the engine bay before patting myself on the back. About 1 minute later the car died and would not start back up. I plugged in the old transistor and the car was back to the original state.
Replaced power transistor with a second used one. The car started but was only firing on cylinder 2 and 3. I then plugged the power transistor from the previous day in and it fired up, but again only cylinders 2 and 3 were firing. (One other thing to note is that all transistors provide an appropriate tach signal to my gauge cluster.)
Because of the results of the 1st used transistor, I figured that maybe a wire in the harness was grounding out and breaking the power transistors, so I checked the continuity of the following wires: wires going from the 1g CAS (cam angle signal wire and crank signal wire) back to the corresponding pins in the ECU plug; the ignition signal wires from the ECU to the transistor plug, the wires from the power transistor plug to the coil packs. All of these had continuity. I turned the ignition to the 'on' position and checked the voltage at the power transistor plug and the CAS plug. Both were about 12 volts. Ground wires also checked out.
I checked the resistance of the coil packs (both main and secondary resistances). The main resistance was checked using the coil pack harness and was coming out as 1 ohm on both coil packs. The Haynes manual calls for a max of .7 ohms, but since the coil pack for cylinders 2 and 3 were working, I chalked the readings up to the inaccuracy of my harbor freight mulitmeter. The secondary resistances were within spec.
I changed the CAS with a used one. This had no effect.
Finally I changed the ECU with a known working ECU. This had no effect.
I'm pretty much out of ideas right now. It feels like I've change/checked every part of the ignition system. Is there something I might be missing or any other tests I can perform? Any help would be greatly appreciated.
Anyway, the background. I drove the car into work Wednesday morning and it was running great until I drove over the speed bump at the plant's entrance. I went over it slowly and there were no clearance issues or scraping. As soon as I got over it, the car started running poorly. I got out and started pulling plug wires and found that cylinder 1 & 4 were not sparking.
I've done a good deal of searching and based on previous results I've tried the following:
Replaced coil pack for cylinder 1 and 4 with a new Auto Zone part. This had no effect. I also swapped plug wires around with no effect.
Replace power transistor with a used one.The car s fired up great and was running on all 4 cylinders. I got out to check a few things in the engine bay before patting myself on the back. About 1 minute later the car died and would not start back up. I plugged in the old transistor and the car was back to the original state.
Replaced power transistor with a second used one. The car started but was only firing on cylinder 2 and 3. I then plugged the power transistor from the previous day in and it fired up, but again only cylinders 2 and 3 were firing. (One other thing to note is that all transistors provide an appropriate tach signal to my gauge cluster.)
Because of the results of the 1st used transistor, I figured that maybe a wire in the harness was grounding out and breaking the power transistors, so I checked the continuity of the following wires: wires going from the 1g CAS (cam angle signal wire and crank signal wire) back to the corresponding pins in the ECU plug; the ignition signal wires from the ECU to the transistor plug, the wires from the power transistor plug to the coil packs. All of these had continuity. I turned the ignition to the 'on' position and checked the voltage at the power transistor plug and the CAS plug. Both were about 12 volts. Ground wires also checked out.
I checked the resistance of the coil packs (both main and secondary resistances). The main resistance was checked using the coil pack harness and was coming out as 1 ohm on both coil packs. The Haynes manual calls for a max of .7 ohms, but since the coil pack for cylinders 2 and 3 were working, I chalked the readings up to the inaccuracy of my harbor freight mulitmeter. The secondary resistances were within spec.
I changed the CAS with a used one. This had no effect.
Finally I changed the ECU with a known working ECU. This had no effect.
I'm pretty much out of ideas right now. It feels like I've change/checked every part of the ignition system. Is there something I might be missing or any other tests I can perform? Any help would be greatly appreciated.
