Miss fire on #3-no spark...out of ideas-SR20DET-

[5upra]

SR20DET redtop in a 1990 240sx
Well I have been waiting to get a ignitor chip...so I install it today start the car and there is still a continuous miss fire on the #3 cylinder. I have checked the wiring for resistance...nothing. I have swithed coils...nothing. I have changed plugs...nothing. I have checked voltages from ecu...fine. I can't think of anything else to do....besides junk it. I thought I was going to be a mechanic as I have completed 3 school years worth of automotive, but I can't even figure out my own car . I have been through the FSM more times than I care too. I don't get it
Any suggestions would be appreciated
look me up on aim Djclarkgm for real time talk

[trybal]

kinda like mine, mine will fire fine, and then just stop randomly untill the car is cold..?? weird

[MegasquirtCA]

SR20DET redtop in a 1990 240sx
Well I have been waiting to get a ignitor chip...so I install it today start the car and there is still a continuous miss fire on the #3 cylinder. I have checked the wiring for resistance...nothing. I have swithed coils...nothing. I have changed plugs...nothing. I have checked voltages from ecu...fine. I can't think of anything else to do....besides junk it. I thought I was going to be a mechanic as I have completed 3 school years worth of automotive, but I can't even figure out my own car . I have been through the FSM more times than I care too. I don't get it
Any suggestions would be appreciated
look me up on aim Djclarkgm for real time talk

Um did you bother to check compression or do a leak down test? Also check your injector.

[5upra]

healthy motor...just no spark, and there is fuel present on the plug when pulled from head.

[njd07]

had same problem ... got code 21 and was only firing 3 cylinders.

What worked for me:

1. Unplug battery
2. unplug harness from ecu and then carefully reinstall harness to ecu.

worked for me..seems kinda dumb...but always pays to check the little things first.

GL

[SiI40sx]

unplug ur injector see if anything changes if not u have a bad injector, switch out injectors, #3 with #2 and see what happens, i bet #2 will be bad

[tiresmokes13]

sounds like a bad injector to me..

[shaggy240sx]

I had that same problem a while back. Smelled and looked like gas was getting in, but it would never fire (mine was on #1). Mine ended up being a bad ECU...it wasn't telling the #1 injector to spray properly. Smelled like gas but apparently it wasn't getting enough or something, arc tested the plug to confirm it had spark. Try trading injectors like suggested to see if it is the injector.

If that does not fix it...try switching injector plugs (i.e. plug the #2 plug into the #3 injector...might be difficult depending on how tight your wires are)...if the problem follows the plug and not the injector then it is either a problem in the harness...or a problem with the ECU.

[SPX-13]

First arc test the plug. Take #3 coil out with plug and hold about 1/4" inch from a ground surface (ie the head). Then have someone crank the motor. If there is no spark take a voltmeter and check voltage at the #3 coil plug while the engine is cranked. if nothing then continue to trace those wiring back to every connection point retesting for voltage. If you get all the way back to the ecu, then its probably the ecu. If still nothing try unplugging everything and putting it back together.

I had a similar problem with my redtop install, but only my #1 was firing. It turned out to be a bad ecu, but yours sounds more like a connection problem because you have 3 good cylinders. check all the wires around the #3 coil connector and wiring, wiring can get old and create shorts sometimes.

[5upra]

went and did some load testing and the negative wire on #3 coil reads full battery voltage. Can anyone tell me where that wire comes from? FSM isn't much help, cause I sure as heck can't find it.