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Discussion Starter · #1 ·
Well, I've done my fair share of searching, though it seems everyone's misfire issue is all different. First off, my car is a 1993 Miata. I'm going to guess that the misfire has nothing to do with any of the modifications I've done, but about a month ago I did a DDMworks Elk intake, and a TopSpeed exhaust with test pipe.

I noticed it when I went inside of the store on tuesday, came out, and it started on 3, but quickly went back to 4. At work I checked the plugs, noticing that 3 and 4 were coated in oil, which i cleaned off. After work that night, mid way driving home it randomly started misfiring again. Today I start it, and it runs on all 4 for about 2 minutes, and once it starts warming up it starts misfiring again. So far I've replaced my plugs, my wires, and my valve cover gasket, which fixed the oily plug issue. My compression is good across all 4 cylinders, all of which read about 145-150psi. I've noticed when its misfiring that if I remove the wiring from injector for cylinder 3, nothing changes. Which in that case leads me to believe that the injector is plugged, although when I start it, it runs close to normal. All the injectors pass the noid light test, as well all of them click when I do the screwdriver test.

Any words of advice?
 

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A misfire is usually caused by lack of spark not lack of fuel. Pull the plug and wire together and rest it on the cam cover. Pull EFI fuse and crank motor. Look for spark. Repeat for all plugs or do them all at once. The coils in early Miatas seem to be the most common cause of misfires. Wouldnt hurt to look over the ignition wires to the coil packs and CPS too.

What wires, plugs and gap are you runnin?
 

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If it heats up and then starts misfiring.. could be the ignition module... on the 1.6 cars its separate and not in the coils right?
 

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Don't wanna throw too much at you but you're sure the plugs aren't oily again? How long after did you check for oily plugs after plugs, wires, and VC gasket? Being kinda wordy here but what I'm gettin' at is if the plugs are oiled again, your valve seals are shot and would cause misfiring.
 

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Discussion Starter · #6 ·
Plugs were still clean after a days worth of driving, I'm getting spark normally as well as all 4 injectors sound normal when it's running. It sounds like when my old car had a dead injector. Like I said pulling the harness off injector 3 changes nothing.
I'm running new v power plugs gapped at .40 and Belden wires, as they were out of NGK
 

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Discussion Starter · #7 ·
One other thing I forgot to mention. I washed the car on Monday at once of the do it yourself high pressure hose places. I have flyin miata turn signal intakes, and I've heard to try and refrain from spraying into them, but maybe I soaked a ground wire? Though you'd think it would start running odd right after. Where ate the grounds under the hood that id need to look for
 
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