SR20DET Cylinder 4 Not Firing

[Freivo34]

Hey all. So, background: I have a S13 Blacktop SR, pretty much completely stock, has always run like a champ. However, I've had an auto ECU in it since day one, and finally decided to swap it out for a manual ECU to get rid of the annoying rev hang. Yesterday I primed the car (it had been sitting in storage and hadn't been run for a few months) by unplugging the CAS, but the battery needed a jump. Jumped the battery, car started right up, idled perfectly, sounded great, etc etc. I turned it off, swapped the ECU, then went to start it up again and the battery had completely given up.

So, today I went to get a new battery, swapped it out, started it up with the new ECU and could immediately hear (and FEEL) that it was missing a cylinder. Tried swapping coil packs and spark plugs around, problem stayed on cylinder 4. Checked the pins on the ECU plug as well as the ECU itself, they all look fine, the wiring looks fine, I'm at a complete loss here. Also tried the auto ECU from before, no difference.

What could I have possibly fucked up by changing ECUs? Maybe I pulled on the harness too hard? Could it be something else like the ignitor chip? Kicking myself over this, not sure what to try next. :confused:

[Freivo34]

Update, not the ignitor chip. Guess I'm hunting wires.

[Dboyizmlg]

Did you try swapping injector?

[Freivo34]

Did you try swapping injector?

that?s my next step, I?ll make sure to update this if I figure it out in case anybody else has the same issue.

[DiscountPirate]

I'm thinking it has something more to do with the car sitting rather than the swap or wiring. If anything check your harness grounds and plugs, and while you're at it you can confirm coil function to eliminate those. If your gas is getting old maybe it's just running crappy or your filter is clogged so checking fuel pressure is something else you can do.

[Freivo34]

Hey all, so I broke the injector on cylinder 4 trying to remove it in the recommended way using two screwdrivers to pry up on the plastic tabs, as I wanted see if it was leaking or stuck open. Unfortunately, the screwdrivers went clean through the top of the tabs and I had to resort to vice gripping it out. It got pretty banged up from the vice grips, so I ordered a new injector and new o rings, threw it in, and this actually solved my problem.

Essentially, the car ran fine with the auto ECU, and between when I turned the car off and installed the manual ECU the next day, that injector either died or stuck open. I believe it was stuck open due to the raw gas smell from the car when it ran on three cylinders.

Moral of the story, just because you recently changed something, doesn't mean your new issue is from that! Thanks for the suggestions everybody! :coold:

[Dboyizmlg]

Hey all, so I broke the injector on cylinder 4 trying to remove it in the recommended way using two screwdrivers to pry up on the plastic tabs, as I wanted see if it was leaking or stuck open. Unfortunately, the screwdrivers went clean through the top of the tabs and I had to resort to vice gripping it out. It got pretty banged up from the vice grips, so I ordered a new injector and new o rings, threw it in, and this actually solved my problem.

Essentially, the car ran fine with the auto ECU, and between when I turned the car off and installed the manual ECU the next day, that injector either died or stuck open. I believe it was stuck open due to the raw gas smell from the car when it ran on three cylinders.

Moral of the story, just because you recently changed something, doesn't mean your new issue is from that! Thanks for the suggestions everybody! :coold:


I?m glad you fixed the issue!