That guy means that the car will start to turn over but not run. When my crank sensor went out in my Jeep, it was not reading any of the pulses that get picked up by the sensor. The sensor was bad, and had been going bad by being more noisy (picking up gaps when there were none). The sensor reads metal, and then when there is no metal it reads the pulse. I don't think goo would matter.

Once the sensor was fully bad, if the computer doesn't read any pulses it shuts down the coil and the injectors both. I believe this happens quick like within a few cranks.

Also if you haven't tried already, try swapping your plugs around.

 

"Also if you haven't tried already, try swapping your plugs around".

Everything I've investigated tells me the spark (to about half the cylinders) is weak and intermittent before reaching the plugs, but just in case I'm wrong about that, I'm going to slam in a new set on Monday. They're pretty new, and look OK, but plugs are cheap. (Glad something still is).

Thanks for the info on the ability of the CKPS to become sketchy. I might have to drop the big money on one, since this is driving me nuts.

It could take a while, but I will definitely post the resolution to this problem, if and when I find it.

 

Also if memory serves (yikes...) the crank pos sensor is only used when starting the car so the pcm can tell where the crank stopped last and where its at when attempting to start.

Good luck tomorrow!

http://www.dodgeintrepid.net/showthread.php?t=193775

 

All of the notches in the flywheel/flexplate are exactly the same. They only trigger the sensor, to clue the PCM in that A cylinder is approaching firing position. That's it. If the PCM is getting the signal AT ALL, it will fire the coil. Distributor handles which plug it goes to, PCM doesn't care.

PCM determines which injector to fire (and when) by using the cam sensor, in combination with the crank sensor. Cam sensor is an On/Off deal. It switches state every crankshaft revolution. So, in order to 'index' which injector the PCM needs to fire, the engine has to roll over at least one revolution, so the cam sensor will switch state. (from on to off, or vice versa.) When the cam sensor changes state, the PCM knows which cylinder is next in firing position, so, it times injector pulse accordingly.

Both sensors are constantly monitored by the PCM, they both play an active role in running the engine, if either fails, engine won't run......

So, going by your symptoms. Engine runs, just not very well, and you have weak/intermittent spark on several cylinders consistently..... and you have changed everything in the secondary circuit..... its gotta be the primary circuit that is causing the issue. Either intermittent power feed TO the coil, or intermittent inadequate ground to charge the coil. (coil builds charge while it is grounded, when ground is interrupted, the magnetic fields collapse, causing a surge of current in the secondary windings, which is what actually produces the spark.

I think the only real way to determine what is really going on here, (without just swapping more parts...) would be to put an oscilloscope on the coil, and see what power and ground are doing. Is the coil not being sufficiently charged on occasion? Or, is the ground not going completely open, so the magnetic fields weaken, but, don't completely collapse, thus, not getting quite the 'ooomph' behind the spark.

 

I would ground out the coil wire and see if all sparks appear to be the same coming from the coil. If yes, I would inspect the distributor for wobble in the drive shaft (bearing going out).

It's also possible the new cap could be slightly out of round or the button on the rotor is making an intermittent connection with the coil tower.

 

I wasn't going to bother with this thread anymore, but, do you have any misfire codes? I'd remove 1 plug at a time and check the spark at the plug , not with a screwdriver a 1/4 inch away with the wire. Even with doing it at the plug itself, you can only reach certain ground locations. Rust thickness, paint thickness can have an effect.

 

What Magnum does not have a problem with a blown plenum and a clogged cat?

 

aim4squirrels - "I would ground out the coil wire and see if all sparks appear to be the same coming from the coil. If yes, I would inspect the distributor for wobble in the drive shaft (bearing going out)".

I've already done both; it's very hard to tell if the coil spark is entirely regular because they come 8 times faster than at the plug. I need some better diagnostic tools. The distributor checked out fine; very little play anywhere.

zman: "I'd remove 1 plug at a time and check the spark at the plug , not with a screwdriver a 1/4 inch away with the wire".

If I'm not getting a strong, regular spark at the end of the wire, I don't care what the plug is doing, for the purposes of fixing my problem. And I still don't understand why you condemn the screwdriver method, when our gas vehicles run on the principle involved. And I know how to determine a good ground spot.

***

More interesting info:

Occassionally, cylinder 4 does not fire at all.

Yet more interesting info:

This engine has been acting quirky for years. It has had a gremlin somewhere that causes it to stall out on what seems to be aa seasonal basis; if I recall correctly, during the colder months. It seems more and more likely to me that it's the PCM, since the sensors seem to be sensing, and it's the PCM's job to do something intelligent with that input. I'm thinking that there's some bad circuitry in it involving the controlling of cylinders 4, 5, 6 and 7. It might just be a coincidence that those cylinders are sequential in number (though not in firing order), or maybe it has to do with how the circuits are designed in the computer; those circuits might be physically close to one another, and defective.

I'm going to get another PCM, put it in, and report back. Thanks for all your help, and if there's anyone who has ever had a problem like this resolved by replacing the computer, I'd love to hear about it.

 

Same circuit controls spark for all cylinders. If that circuit is flaky....... then you get flaky behavior. Yours is consistently flaky, which is a real puzzler.

Edit: Have you tested the spark at the coil, and verified that you get intermittent weak spark?

 

Now I could see that being a coolant temperature sensor malfunction, the PCM adjusting fuel trim and screwing it up with bad readings..

FWIW... ymmv.. etc. etc.

Edit: That might also affect spark advance.

Edit 2:
Here, poor mans oscilloscope

.. build that, put the probe up to the harness from the PCM that goes to the coil.. try to keep the engine under 96000 rpm's, and let us see the wave.

Edit 3:
Make sure the output voltage from the PCM to the coil is not higher than 5v before hooking it up.