94 3.2L suddenly running really bad

[2eyefishclaw]

Thinkin Of Somtin I Once Had One With Same Symptons And Would Also Die Out At Times
Found That The Ckp Wiring Was Caught Up Under The Engine Mount And Was Intermittantly Shorting Between The Mount And Frame

[trooperbc]

like most input components for the computer, the reference voltage *to* the sensor should be ~5 volts. and you should get a reading *from* the sensor (to the computer) of ~2.5 volts when cranking. first test for reference volts, then output.

sounds like the short idea might be it, doesn't it...

//bc

[Cat Fuzz]

Originally Posted by trooperbc

like most input components for the computer, the reference voltage *to* the sensor should be ~5 volts. and you should get a reading *from* the sensor (to the computer) of ~2.5 volts when cranking. first test for reference volts, then output.

sounds like the short idea might be it, doesn't it...

//bc

Doesn't the CKP induce its own voltage? I don't think there is a reference voltage. Also, the CKP doesn't connect to the ECM, it connects to the ignition module.

[trooperbc]

Originally Posted by Cat Fuzz

Doesn't the CKP induce its own voltage? I don't think there is a reference voltage. Also, the CKP doesn't connect to the ECM, it connects to the ignition module.

it's true that info came from a newer, later application; but the idea is the same, the ignition module gets the reference voltage from the ecm and the crank sensor gets it from the dis module. the test for reference and output voltage should be instructive.

however, from what what you've said before and what i suggested concerning the ignition module and coils still apply. there can be, and often is, a difference in under-load and idle conditions. i would suggest attempting to isolate the problem to a particular coil by observing either the timing light or by disconnecting spark plug connectors and observing the spark across a gap to ground with the engine reving. of course if you had a spark tester, it'd be alot easier and surer.

by either method, if you find a problem wire (probably two because each coil powers two cylinders), then you can swap coils, they are interchangeable, and see if the problem follows.

//bc

[surferfletch]

I am clueless about diagnosing electrical problems, but the Haynes I have says that reference voltage is 5 volts.

[Cat Fuzz]

Originally Posted by surferfletch

I am clueless about diagnosing electrical problems, but the Haynes I have says that reference voltage is 5 volts.

I no longer trust my Haynes/Chilton regarding sensor readings. I thought I had nailed the problem with a bad MAP sensor but it turns out that the repair manual is giving the wrong voltage readings for a good sensor.

I can safely say that it isn't a fuel delivery issue. Hooked up a fuel pressure gauge and drove it till it died again and still had fuel pressure.

Anyway, back to scratching my head on this.

[Cat Fuzz]

Ok, a little update. I went out and bought 6 inline spark testers with the lights in them. Hooked one to each spark plug wire at the coil packs and then drove around and waited for it to croak. Seems like it takes longer and longer to screw up but when it finally did stall, I popped the hood and tried to restart. Took a lot of cranking to get it to restart but I had good spark at all six cylinders and good fuel pressure while I was cranking it. Now, I'm even more baffled than before. The only thing I can think of now is I may have a fuel injector or two trying to crap out.

Anyone have any ideas now?

[syddavis]

How did this one turn out... what was the problem? I've got the exact behavior on my '94 Rodeo and haven't got a clue. Thanks.

[Cat Fuzz]

I never did find the problem. It just went away on it's own. I can only guess that I got a bad tank of fuel. Once that fuel was gone, it started running normally again.