97 Caravan bucks and stalls Help

I have a 1997 Dodge Grand caravan with 110K and a 3.3L engine. Over the
July 4th weekend the engine would not start. Turned over but NS. Had the cam
sensor replaced. Ran fine for 2 days and started bucking and stalling.
Replaced coil pack. Same problem. Changed computers, Same problem. Put the
original computer back in so the dealer could scan it. But the codes had
cleared. Plugs, wires and a crank sensor made no difference. My regular
mechanic scanned it(Codes set were 12, 43, 55) and said it indicates a
problem with primary circuit #3, which affects Cyls 3 &6. He drove it around
all day on errands but so far it has behaved any Ideas Would be appreciated.
Last week it bucked and hesitated so bad an axel shaft snapped. Thanks Jay

 

Also We noticed that when it is about to stall the RPM's jump to 1100-1200
then drop to 500, then back to 11 and drop again till it stalls.

 

Sounds like a dirty throttle body if it idles rough and occasionally dies at
lights. Given what has already been replaced, another possibility is
clogged/dirty injectors. I'd shoot for the TB first as this is a regular
maintenance item every 30K and sounds like it is long overdue.

Bob

 

Put a scope on the O2 sensor. I had a 1994 GC with 3.3 engine. At
about 150,000 kms, the O2 sensor went, and never set an engine fault
code. Got all kinds of "spit back", hesitation, slugish under load....

It took my shop 5 min to diagnose, 10 minutes to replace, and 15
minutes to write up the invoice!

 

A dirty thorttle body or injectors will not cause a primary coil fault
code. since the coil was already replaced the only thing left to check
would be the wiring going from the coil pack to the PCM.
Disconnect the PCM measure the resistance of the Ign coil #3(red yellow
wire) driver circuit to ground, if the resistance is below 5.0 ohms find
and repair that wire for a short to ground.if it isnt below 5.0 disconnect
to coil connector and measure the resistance from the PCM (cavity 2 of the
PCM)to the connector checking for a broken wire, if the wire is not below
5.0 ohms find and repair the open wire. if it is below 5.0 replace the
PCM.

Good luck

Glenn Beasley
Chrysler Tech

 

A dirty throttle body was mentioned a couple times along with
maintenance that should be performed at 30K. What is the reccomended
procedure for cleaning a throttle body?

Ken

 

Go get a can of Throttle Body cleaner (NOT "CARB" Cleaner). Disconnect
all the wires from the throllte body, and remove it. Take off all the
little bits and pieces. Use the cleaner and an old tooth brush, and
throughly clean all the surfaces and orofices in the throttle body.

Reinstall all the bits and pieces. Reinstall the throttle body in the
van. Reconnect the wires and ducts.

That is about it.

You can try just spraying the cleaner into the throttle body while
mounted on the van, but this does not ensure that everything is
completely clean. If you are having problems, for all the time and
effort it takes, you are better of to throughly clean the throttle
body and in so doing remove it as a possible cause of problems.

 

Wow That cause sounds just like what my mechanic was saying. He said he
checked out the wiring yesterday but wanted to see if he could duplicate the
problem with a scope hooked up while he drove it. I'll give him your
response in case he hasn't already done it. The problem isn't constant, so
it might take a couple of days to duplicate it. I'll let you know how it
comes out.

 

It is too hard bouncing from forums to Email. I will answer that in here .
"Mechanic checked the wiring and it checked out good. He did a throttle
body
cleaning after the van missed, bucked, and stalled while he had it out.
while they were cleaning the throttle body the cleaner was coming out
of the
EGR valve body. Could that have been one of the problems? Might account
for
the raising and lowering of the RPMs. Also the coil pack was replaced
with
an aftermarket one from PEP Boys when we got stuck over the July 4th
weekend. Is it possible the bucking and misfiring could be a defective
coil
pack? My mechanic says the computer never set any codes even when it
ran
like crap



A dirty throttle body will cause those exact symptoms except it will not
set the fault code that they found and will not miss. It will cause a
fluctuation and a stalling condition when the foot is off the gas pedal. Yes
it is possible that it is was a faulty coil pack or even a loose connection
at the coil pack. I guess im lost as far as what time the fault code was
set!!!
Time will tell if it is the throttle body or something else. I would guess
you still have a problem.
Keep us posted.

Glenn Beasley
Chrysler Tech

 

Well, Christine the haunted caravan just spent the last 2 days at the
shop. He changed coil packs with a known good one and it made no difference.
Still bucked and stalled. Put the replacement one from Pep Boys back on. Now
when it acts up, no codes get set. I had him replace the leaking EGR valve.
But he still hasn't had a chance to test drive it. He said that a bad EGR
doesn't always set a code. So, I'm hoping The EGR does it. We're out of
options. He said the last 2 times he drove it once it ran fine and the next
time he drove it with a fuel pressure monitor hooked up it had 50lbs of
pressure right up till the point the engine quit. so the fuel pump is good.
The wiring was checked between the coilpack and computer. OK. If the EGR
doesn't do it , we're stumped. Let me know if you have any other ideas.
PLEASE Thanks Jay Margolis

 

An EGR valve will not fix this problem!!! Find out how many key starts are
monitored by the PCM when this happens. In other words, the PCM counts every
time the engine is started, it will do this to a full count of 255 starts.
So if there are 5 starts now and the problem occurs...check to see if the
counter starts all over again to 0 starts. A scanner will have to be used to
see this.
Also what you can do is with a rubber hammer or something similar, hit the
PCM while the engine is running and see if the engine shuts off or stumbles,
if it does replace the PCM.

Glenn Beasley
Chrysler Tech

 

Well, We thought we had it, but nooo. Still did the exact same thing. My
wife started out for work this morning but had to turn around. It started to
buck and run rough. She stopped and it stalled. After about 3 tries it
restarted. but ran badly to the shop. Our reg mechanic said he did all he
could. So it's back in the driveway. Ran fine from the garage home. No codes
set.
I talking with a customer at work, he said a friend's Mopar did the same
thing. It was finally traced down to a sloppy timing chain. Sounds feasible.
110K on it. Might it be as the computer tries to adjust for the timing being
off, that's when it bucks and the RPM's at a stop waiver between 400 and
1200. All the electrical possibilities seem to have been addressed. Also
tried to tap the computer, as you suggested, while running in park with no
change. As I mentioned in a previous post I changed the computer out with
one of the same from the same year, make , model, and engine as mine. but it
still did it's tricks. Original PCM back in. Going to take it tomorrow to my
brother-in-laws friend who runs his own shop and was a Chrysler tech for
about 25 years. Hope he's seen the same tricks before. What do you think
Glenn?

 

that egr tvalve has to be looked at closer and i do believe there is some issues
with the map sensor wiring

 

have him remove the fuel filter and try and blow thru it (don't inhale while
your lips are on it) it shopuld allow air to pass real easy if not then it's
clogged

 

a egr leaking will not cause a stall condition!!!
that is trhe most assnine thing i ever heard a tech say

 

What speeds does this occur at? does it happen at highways speeds? A Timing
chain would not cause that problem either.Did you find out how many key
starts were set as I stated in my last reply?