940 no spark lh2.4

been a while, but this thing has me stumped. 93 940 NA automatic lh2.4

I've changed the crank position sensor, coil, radio suppression relay thing, powerstage, ecu, icu, maybe some other parts too. can't remember, been throwing parts at it for months

the car will run fine, then randomly, it'll not start. it will crank over and over but no spark(checked with timing light coming off the coil wire). then magically it might just start sparking and run like normal. sometimes during cruising I can feel the engine cut out and see the rpm drop about 500 revolutions and then pick back up a second later - like the automatic kept the engine turning for it to start working again. it also might cut spark while slowing to a stop sign and die

but then, it'll drive fine with no problem for weeks and weeks and I think I fixed the problem only for it to show up again. I thought maybe it was some kind of security thing and my key was worn down so I tried my spare key and same thing. I really don't know how many more parts are in the ignition system and I'm thinking is it in the wiring? there's no visible damage anywhere, doesn't look like a flood car or anything

How's the condition of the coil to distro wire?

I would carry a noid light around and see if it's also a no fuel injector pulse situation at the same time.

You want to do as Z suggests and be ready to trouble shoot. Intermittent issues are the toughest because when it happens is the only chance for testing.

Plus all too often it can be a couple of things on that old car are bad or out of spec causing your issues. For example: Spark plugs with a gap so large that it makes the car hard to start randomly. That along with an intermittent crank sensor can cause these issues and frustrate you when it isn't sorted out with one part.

ZVOLV said:

I would carry a noid light around and see if it's also a no fuel injector pulse situation at the same time.

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I'll toss my set in the car, but I'm pretty sure it's still getting fuel because I've had it flood and when I pulled the plugs they were wet - but that was when it first happened and I wasn't sure if I was missing fuel or spark

oifish said:

How's the condition of the coil to distro wire?

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looks good, I guess I could toss another on it, pretty sure I have a spare one

edit: nope, spare coil wire didn't fix it

If it is getting fuel and there is no spark. That usually means something in the secondary ignition is the culprit. The fuel injection ecu uses the engine speed signal from the coil so if that wasn't switching. There would be no fuel either.

EZK gets rpm signal from crank sensor and then sends a signal over to the LH box directly.

You could do voltage drop tests on connections, such as at the coil. Read on how to do.

You could also check the input into the powerstage when there is no spark. It's a 5v square wave. I would use a scope. You may have some success with a meter. An LED test light may work too.