I accidentally caused a short and now my car misfires.

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Car: 1993 Nissan 240SX

I accidentally caused a short and now my car misfires.

Postby slowbys13 » Sat Aug 06, 2022 5:46 pm

I just bought a 1993 Nissan 240sx Coupe, which came to me SR20DET swapped, but non-running. I got it running by cleaning the MAF, and fixing the fattest vacuum leak I've ever seen. It ran, idled, and pulled hard. But, because the idle set screw was too low, the car would stall out when I came to a stop. I read that adjusting the idle set screw higher, and resetting the idle would fix that. I went to adjust the screw, without disconnecting the negative battery terminal, and touched the ratchet to the positive battery terminal. It created a spark, and the ratchet welded itself to the idle set screw, and the car hasn't run correctly since. It is super sluggish on acceleration, idles like it's misfiring, sounds like it's misfiring, and shakes like it's misfiring.

I have checked all the plugs, coils, injectors, fuel pump, MAF and TPS voltage, all the fuses, and relays.

Please help I leave for college in 1 week and I need to get this car running by then.

And don't come at me calling me stupid for buying someone else's project car or for not disconnecting the battery terminal. I know. I'm facing the consequences of my actions.

Any help would be greatly appreciated.

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2004 Nissan Altima 2.5 S

Re: I accidentally caused a short and now my car misfires.

Postby VStar650CL » Sun Aug 07, 2022 6:10 am

If you haven't read the codes, you need to. It's possible you zapped something that made the ECM go limpy but that's easy to clear. See EF&EC-40 (PDF page 140):
https://www.nicoclub.com/service-manual ... _240sx.pdf

That said, for an average battery, those sparks had about 6 kiloWatts of energy and the air discharges probably exceeded 1000 volts. So it's also entirely possible the EMF melted some protection diodes and trashed your ECM.

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