Camshaft and Crankshaft Sensors--I'M BACK

My saga is found here:

http://groups.google.com/group/rec.autos.makers.chrysler/msg/2ce8507d97431792?dmode=source&hl=en

Here is what has happened since the crankshaft sensor, camshaft
sensor, and power control module was replaced.

Vehicle ran good for a couple of weeks, then would occasionally die at
idle while at stop lights. This would happen perhaps 1 out of 3 days
the car was driven. At highway speeds it would violently jerk--once--
while temporarily lighting the Service Engine light. The jerking was
more consistent.

I took it back to the dealer that installed the power control module.
There were no stored codes. They suggested that I replace the spark
plugs and plug wires and clean the throttle body and fuel system with
chemicals. They had pulled a spark plug and its gap was at .090,
should be .050. They said once the plugs and wires had been replaced
and fuel system cleaned it should take care of it, but if it still
exhibited the symptoms I should take it back to them.

I cleaned the throttle body area with 3M Throttle Plate and Intake
Cleaner. Didn't do a super thorough job since I Ieft the part intact
and sprayed and wiped with a rag inside the throttle body cavity.
However, this seems to have stopped the problem with the vehicle dying
at idle at stop lights.

Now all that remains is the violent jerk and temporary lighting of the
Service Engine light. Curiously, this symptom always occurs at the
same area of my wife's drive to work. In fact, she says it is
predictable and anticipates when it will happen. She's rarely
disappointed.

I don't think it is elapsed time the engine has been running, nor is
it distance traveled. I'm thinking it's related to engine temperature.
But what? I doubt this is spark plugs causing this problem. One jerk
at about the same time after engine startup and momentary flash of
Service Engine Light. Again, when the dealer hooked up the scan tool
there were no stored codes.

So, any ideas? Temperature related problem? Some sensor hiccuping?

 

Not sure if it was on '97 models, but there was a TSB that dealt with
a problem like this. It involved removing the knock sensor because it
would cause the PCM to reset while driving.

 

Hey thanks! I'll research it...

 

Can someone that has access to Chrysler technical service bulletins
please post #19-34-98? I believe it is dated 11/27/1998. I found this
while searching Yahoo Groups. It may contain the solution to a long
running problem. Thanks.

 

not a good number

 

18-34-98 is a TSB that requires disconnecting and taping the wire of the
knock sensor for a symptom you are describing BUT this only occurs if the
Module is resetting itself back to zero and all the learn values resets. A
scan tool is required to determine if this is what is happening.

Glenn

 

18-34-98 is a TSB that requires disconnecting and taping the wire of the
knock sensor for a symptom you are describing BUT this only occurs if the
Module is resetting itself back to zero and all the learn values resets. A
scan tool is required to determine if this is what is happening.

Glenn

 

It doesn't take a scan tool to determine if disconnecting the knock
sensor eliminates the symptoms.

 

No it doesn't. But the OP stated that it happens sometimes, a scanner would
have determined that the PCM went into a reset mode and cleared all learned
values

Glenn

 

find a shop that has a bore scope and have the flex plate checked for cracks/breakage and jambed
into place
i have one if you are near brighton michigan

 

Considering the MIL gives a flash and there are no stored codes, I'd
bet the PCM is resetting. Another trip to the dealer that didn't even
bother checking for TSBs, even after repeat visits, is not what I'd
recommend.

I'd disconnect the knock sensor and drive it. If the symptoms stop,
then it was resetting because of the knock sensor. If the symptoms
remain, a scan tool (in the right hands) would be in order.

 

I might try that, but how would a cracked flex plate cause the
symptoms to occur at almost the exact same time every time the car is
driven?

 

Hmmm...so the scan tool can determine if the PCM is resetting back to
zero and erasing any stored codes? If so, shouldn't the dealer have
told me that the reason the PCM doesn't have any stored codes is
because it's been resetting itself?

 

Well, you just answered my first question that I posted about 30
seconds ago. A scanner can tell if the PCM went into reset mode.

Now I wonder if the dealership knows this and sold me a PCM that I
really didn't need.

 

Sounds like a reasonable suggestion. Can anyone give any reasons why I
shouldn't disconnect the knock sensor?

 

A good scanner can give the user the info. It's up to the user to
interpret that info.

If I remember correctly, you were still getting cam or crank sensor
faults before the PCM was replaced. You haven't mentioned any since it
was replaced. Could be you've had 2 different problems.

 

Yes, using the Co-Pilot device the stored codes were simultaneous cam
sensor AND crank sensors faults. Since I had already replaced them
they suspected the wiring between these sensors to the PCM or the PCM
itself. The wiring checked out OK, so that left the PCM as the most
likely source of the trouble.

I suppose it could be that I've developed another problem since the
PCM was replaced that is causing the PCM to reset itself. When the
dealership said there were no stored codes, I wonder if they checked
to see if the PCM was resetting and clearing them out. I guess I'll
call them tomorrow and ask about that and also the TSB.

 

Hmmm...so the scan tool can determine if the PCM is resetting back to
zero and erasing any stored codes? If so, shouldn't the dealer have
told me that the reason the PCM doesn't have any stored codes is
because it's been resetting itself?


Like it was already posted, a tool is only as good as the person using it,
but yes it can see that everything has been reset. disconnecting the knock
sensor if so equipped wont hurt, but not your problem. The TSB you are
referring to is a one time occurrence while driving, it WILL NOT cause
severe bucking or constantly surge. What you would experience if this was
the problem with a knock sensor would be a quick surge as the PCM reset
itself. and then run fine until a next start up.

Glenn

 

This is exactly what happens. One sudden jerk, flash of the Service
Engine Light, then everything back to normal driving. Next day, same
thing, at about the same distance/time traveled.

 

You could have disconnected the knock sensor in the same amount
of time it took to post.