So i have just come across a problem with my 93 impreza where it only fires on 3 cylinders. Here is what i have done so far but i am now stumped.

Replaced spark plugs - no difference
Replaced coil pack - no difference
Tested injector - works fine
Compression test came back @ 160psi


What now?

 

ignitor module replaced?

 

I have individual coil packs for each cylinder so its all built ( i believe), so yes it has been replaced.

 

Sorry read it wrong no i havent replaced the ignitor unit

 

Is it still on the early coil packs? or been upgraded to new age coils?

 

Early coil packs

 

Was the replacement coil pack new ?
they are very easy to damage, if you move the coli pack to a another cylinder does the miss remain on the same cylinder ?

 

maybe worth trying an ignitor module?

 

Yes and no the problem stays in the same cylinder

 

Just went a bought one from the local shop and no fix, any other ideas?

 

is it the lead or a poor connection

 

Check you're getting a spark. Coil pack plugged in, dummy plug fitted and earthed and crank engine. Do this safely obviously.


Check the injector is being sent it's power. I use a noid light which plugs onto the injector plug and start the engine to see if it flashes.


Found out what it's lost and work from there

 

So i finally got round to working on the car and still havent fixed the problem here is what i have done since.

Did a coil pack upgrade to 02 wrx coil packs. Tested each cylinder was getting a spark which it is.

Then i went onto the injector and found that while it was on the car it was not operating to the same extent the others where, i used the simple screwdriver trick and could not hear it clicking. Once i opened up the throttle i could hear it clicking very lightly. I immediately thought wires, so i tested the wires from the ecu to the injector (signal wire for that cylinder is B44 pin 13) and had continuity in the wire. So there is no break in the signal wire. I then tested the power wire which is the yellow and red one next to it and that also has continuity.

P.S i tried 3 different injectors on that same cylinder to make sure it was not the injector.


What now? Tempted to take the power wire from the cylinder behind it and connect it up via that way and then run a direct wire from the signal wire at the ecu to the plug and see if that fixes it?

Oh and finally i have tried a different ecu and no fix.

 

did you do the same electrical test on all 4 to get a comparison ?

 

Yeah tested all 4 to make sure they had the same continuity