97 Caravan bucks and stalls Help

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 sh>Also We noticed that when it is about to stall the RPM's jump to 1100-1200

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

damnnickname wrote:

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.

appreciated.

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?

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?