1996 Grand Voyager bucks at idle in gear, but not in neutral or Park

The subject pretty well describes the problem. My 1996 Grand Voyager
with the 3.3L/4 speed drive train began to act up on me today. The van
has 175,000 miles on it and I was nearing the end of a long road trip
and stopped for gas. The van had been cruising the previous 3 hours at
65 MPH. As I was pulling out of the gas station, the van bucked pretty
violently shaking the van smartly. The tach jumped around between 1,000
and probably less than 400 RPM. The van didn't completely stall, but
came very close. Once I got some throttle in and got above 15 MPH or
so, the van smoothed out.

The van ran fine at speed, but when I got near home and had to go
through town, it would this at every stoplight, ocassionally stalling.
It would restart instantly and idle great in park or neutral, but as
soon as I shifted into D or R, it would buck like a bronco until I got
it moving a little.

Some time back, I had similar symptoms when my fuel pump was failing,
however, there was one major difference and that is that before shifting
into neutral didn't help. The service manager at that time thought it
might be the torque converter locking up inadvertantly, but he changed
his mind once he heard that shifting into neutral didn't help the
problem. Since shifting out of gear now does help, is this possibly an
indication that this is the torque converter clutch intermittently
locking up? Are there other failure modes consistent with these
symptoms? Which sensors does the transmission controller use to decide
when to engage the clutch?

Matt

 

When was the throttle body last cleaned thoroughly? How old are the plugs
and wires? Are the fuel injectors working properly or could they be
partially blocked?

I'm not as quick to blame the transmission. I just think you are seeing
this because of the load when at idle.

Bob

 

Throttle body was cleaned about two months ago. Plugs and wires were
replaced 25,000 miles ago along with the coil pack. I can't say for
sure on the fuel injectors as I don't know how to determine if one is
partially blocked, but it seems like that would cause problems other
than just at idle in gear.

Could well be. That is why I'm asking what other failure modes would be
consistent with these symptoms.

Matt

 

My thoughts: I'd start by looking at the three front plugs to see how they
look and if they provide any indication of being fouled. I'd then clean the
TB again making sure to disassemble and clean the AIS using throttle body
cleaner, a toothbrush, and some clean rags. I'd use new gasket to
reassemble and see if this eliminated the problem. If not, then it still
could be an AIS problem, a stuck EGR (but you did not indicate any error
codes), or a bad spark plug or wire though they were replaced 24K ago, or
even a tank of bad gas. I'd probably also throw a large bottle of Techron
injector cleaner into a full tank as well. As a last resort if none of this
helped and before taking it in for service, I'd probably change all 6 plugs.

Good luck. Let us know what you determine is the cause.

Bob

 

If the transmission is original I would be rather suspicious of it. Here's
some things to try:

Try starting out in 1 gear instead of in D and see if the problem goes away.

If your going at 15Mph and you stop on the gas, does it buck again?

Does it buck when your at high speed and your going up a hill with
the pedal to the floor?

Ted

 

It acted up in D, 1 and R.

Didn't try that and the problem hasn't recurred since the day it
orginally happened.

Didn't try that either. I will if/when it acts up again.

Matt

 

Sounds like a major vacuum leak...like a PCV valve hose. If so, it will
eventually "teach" itself to run with it. Then it will repeat the
episode when you fix the problem.

 

Matt, I had the same problem on my 96. Mine stalled when I came to a
traffic light. I had to start it in neutral, drop it in to drive and
back to neutral to get it moving so it wouldn't stall. Parked it
overnight and the next day no problem. The problem came back about a
week later, only this time you could hear metal grinding. I put in a
Chrysler rebuild.(under warranty thank you) This was at 53K!!, and I
changed the fluid and filter regularly with ATF#3 I now have 110k and
no problems. Good luck.

 

Well, hopefully, I'll have better luck than you, but even so if it dies
tomorrow, I won't feel too badly given that this is the original tranny
at nearly 176,000 miles now.

I had a similar problem once nearly a year ago, but it coincided with a
failing fuel pump so I thought it was related, but I'm guessing now it
was merely coincidental. It hasn't happened all week driving to work,
so maybe it was water in the gas I bought or something. It just
happened so fast after filling up that I couldn't believe the gas could
have gotten circulated through the system that quickly.

Who knows? I'll just keep driving it until it acts up consistently
enough to troubleshoot it reasonably.


Matt