Non Cobra intermittent spark problem...Any ideas?

[Brent Mills]

My wife was driving our 1990 Mitsubishi Montero (why do things always happen when she's driving it? ) and it began to drive roughly....The next day when I was checking it out, I tried turning it over, but it would not start until I released the key from the start position (as soon as the starter was disengaged, it started up), at which time it ran roughly. I turned off and then cranked it over again, and it again started only after I released the key from the start position and it again ran rough.

I then let it run and removed a spark plug wire at a time to see if it was only one cylinder giving the problem (I suspected it wasn't as it didn't run like a cylinder was dead--more random), and I was able to confirm it was a random miss. With that I hooked up my timing light and it confirmed that I was getting random spark skips on all cylinders.... fire ... fire ... fire ... skip ... fire ... fire ... skip ... fire ... fire ... fire... fire... fire... skip ... fire and so on.. Very random.


Ok, now what? Thanks for any help.

[HighPlainsDrifter]

Hi Brent,
Sounds like your ignition module or pickup is failing, on a ford it's inside the distributor, don't know where it would be on a Mits.
Good Luck,
Perry.

[Dangerous Doug]

Same thing happened with my wife's Cherokee. Turned out to be the "crankshaft sensor" in the distributor. Replace it before it completely fails and leaves her stranded. Mine died as I was driving it up out driveway, fortunately.

Another possibility is the the wire going to the ignition module in the distributor. My wife's Volvo had a wire that had become frayed inside the distributor. I had tuned the car and broke off the last of the frayed wire without realizing it. Took a while to figure THAT one out. A soldering iron and burnt finger tips fixed that one.

One last thing I'd check is the coil: My wife's Volvo (glad I sold that thing) was dying while she was driving it. After it cooled, it would start back up and run fine. The coil would get warm and then the expanding metal would create an open circuit. Once it cooled, it would close the circuit and start and run again. The dealer putzed with it for a couple of days and said their was nothing wrong with the car, and then a day later my wife was stranded once again. I got out my Tektronix voltmeter (I used to work at Tektronix) and checked the voltages at the coil poles, then drove the car around until it failed. Once it failed, I checked the voltage again, and one pole was now at ground instead of 12V. Replaced the coil and off it went.

Good luck, and Happy New Year,
Dangerous Doug

[Michael C Henry]

What is the battery and charging system condition like?Voltage should spike whe you release the starter. Voltage may be marginal during starting because of lack of available current. Average battery life is about five years.Does it get even worse with any high current accessories like blower or headlites on?