QuestionQUESTION: Hi, I am lost with this problem. 1996 miata 1.8, died on highway. While there are 2 coils, only 1 is firing. Checked coils resistance and they checked ok. Swapped electrical plugs and the non working coil fired! (1&4) Checked wiring and all looks good. Could this be a ECU problem? Thanks.
ANSWER: In all likelihood your crank angle sensor (CAS) has failed. Yours may or may not also have a magnetic pick up located at the front of the crankshaft pulley, 1996 was a transition year some had both some only had the CAS (depends on the production date). Some diagnostics could be done to narrow and confirm the sensor failure versus a coil or harness failure. The ECU looks to the CAS to determine the "G" signal (top dead center) TDC of #1 and the "Ne" signal 180 degree rotation therefor a resulting failure would cause fire on 1&4 and no fire on 2&3.
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QUESTION: I forgot to mention that the crank angle was changed as well as came sensor!
ANSWER: Swap the coils and see if the problem follows. This will determine a bad coil/good coil, harness or ECU issue.
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QUESTION: As stated before "Checked coils resistance and they checked ok. Swapped electrical plugs and the non working coil fired!" Problem seems to be in wiring or ECU?? Coil does fire a few time then nothing again?? Thanks
AnswerRight, well seems you've done all the preliminary work so the next is line by line harness (seldom a fault without trauma of some kind) or cut straight to the ECU. Check the harness plugs for corrosion, open the ECU and check for corrosion inside, has the car ever gotten water. Any other symptoms exist, typically with an ECU failure more than one problem is presenting.
