91 Gr Caravan 3.3 acceleration problem

Wondering if anyone has any thoughts on this problem with my '91 Grand
Caravan 3.3L. Has 370,000 KM but still in pretty good shape and
working reasonably well.

When going uphill at speeds of approx 80 KPH (approx 50 MPH) engine
seems to "jerk" almost like a sputtering or missing ... but press the
pedal to force a downshift and no more problem! Don't notice the
problem when driving on level or at slower "in town" speeds.

Problem developed actually a couple months ago. A mechanic I normally
trust suggested I get a motor vac done - referred me to a shop with
the equipment to do it. Cost $100 and there's no noticable difference.
In the last few weeks I've also noticed that on a cold start, there
seems to be some hesitation (loss of power)when first starting to
move. This disappears after a minute or so. I assume this may be
related, although this is a recent occurrance.

Rod Corkum

 

What is a "motor vac"?

How much diagnosis of this do you want to do yourself?

You might pull a plug and see if it's showing signs of too lean condition.

Check the air filter and make sure it's not clogged.

You might run it though an emissions test station (if they have such in
your area) and see if it still passes.

This sounds like a fuel system problem to me, I'd start by checking for
vacuum leaks, check fuel system pressure, check for proper function of
EGR valve.

Ted

 

Could be any # of things. Start with looking for any codes. Ods are you'll
get something refering to the O2 sensor. Easy and cheap. When we had the
exact symptom on our old 92 that's what it was. But this "motor vac" what
the hell is that?!
Larry

 

Thanks for the tips. The "motor vac" is a fuel system cleaning
procedure. I did a quick web search and found two sites that seem to
explain pretty well. See www.astauto.com/motorvac.shtml and also
www.allstates.com/fuel%20injector.html (halfway down the page on this
one.)

Also received a direct email suggestion relating to some plug wires
causing a similar problem. So a few things to check out.

 

Thanks for the tips. The "motor vac" is a fuel system cleaning
procedure. I did a quick web search and found two sites that seem to
explain pretty well. See www.astauto.com/motorvac.shtml and also
www.allstates.com/fuel%20injector.html (halfway down the page on this
one.)

Also received a direct email suggestion relating to some plug wires
causing a similar problem. So a few things to check out.

 

I've had what sounds like the same problem with my 96 GV. It began
around the 90,000 mile point and has continued to this day (155K now).
The problem has never set an error code. The dealer said it needed a
TBI cleaning, but that didn't help. They also said it could be the TCC
acting up, but since no codes are set, they couldn't be sure. So far,
nobody has been able to find the problem. Mine occurs close to 45 MPH
than 50, and only a certain throttle settings on certain hills. It
seems to require just the right load at just the right speed to act up.

Does your sputtering go away only if you increase throttle? Mine will
stop with either more throttle or less.

Matt

 

My van (94 GC 3.3) ran weird for MONTHS before it finally tripped a
code - that code was for the O2 sensor.

I had it replaced, and all the little quirks went away.

As it was said - cheap and easy to do. Start with the simple stuff
first.

 

YEah on those years the O2 sensor can get pretty bad before it throws MIL
Larry

 

Oxygen sensors have a very difficult survival job with Canadian gasoline,
most of which contains high levels of Sulphur and MMT -- both of which
tend to coat and shorten the effective life of the sensor. You will not
necessarily get a trouble code until the sensor fails completely; they can
and do get "lazy" (slow to respond) and cause all kinds of weird
driveability faults without setting a code.

When you replace it, make sure to get a Chrysler-Mopar,
Standard-BlueStreak, NAPA-Echlin or NTK sensor, and NOT a Bosch, unless
you want to be right back where you started in a few weeks.

Your mechanic was lazy. He should have done proper diagnosis and
evaluation instead of sending you to spend $100 on a BS process that can
easily be duplicated, when it is actually needed, with a $17 can of BG 44K
or bottle of Chevron Techron.

I'll also ask: How long since you had a proper "tune up", by which I mean
a new set of proper spark plugs (not the gimmicky multiple-electrode
crapola), a new air filter, the throttle body cleaned, the PCV valve
replaced and a complete cleaning and inspection of the PCV system?

DS

 

Yup. The replacement they put in mine was an NTK. I was questioning
the mechanic about them when he removed the old one - which was also
an NTK, and had likely been there for a long time.

The mechainc showed me the O2 signal on the scope. Mine was a
square-wave which did not vary with engine changes. When the new one
was installed, the signal was smooth, and responded fairly quickly to
engine changes.

No doubt about it.

As for the coating, I would agree. For the first 2 weeks, I got 27 MPG
in the city. Now I am right back to about 20 MPG.

 

My 97 3.3 does the same thing at about 40MPH...but I have to have the A/C
running for it to "buck" like is described here. Been doing it for 3-4 years
now..no codes.

| Rod Corkum wrote:
| > Wondering if anyone has any thoughts on this problem with my '91 Grand
| > Caravan 3.3L. Has 370,000 KM but still in pretty good shape and
| > working reasonably well.
| >
| > When going uphill at speeds of approx 80 KPH (approx 50 MPH) engine
| > seems to "jerk" almost like a sputtering or missing ... but press the
| > pedal to force a downshift and no more problem! Don't notice the
| > problem when driving on level or at slower "in town" speeds.
|
| I've had what sounds like the same problem with my 96 GV. It began
| around the 90,000 mile point and has continued to this day (155K now).
| The problem has never set an error code. The dealer said it needed a
| TBI cleaning, but that didn't help. They also said it could be the TCC
| acting up, but since no codes are set, they couldn't be sure. So far,
| nobody has been able to find the problem. Mine occurs close to 45 MPH
| than 50, and only a certain throttle settings on certain hills. It
| seems to require just the right load at just the right speed to act up.
|
| Does your sputtering go away only if you increase throttle? Mine will
| stop with either more throttle or less.
|
| Matt
|

 

PROBLEM SOLVED!!

The first responder sent me a direct email: "The spark plug wires on
cylinders 3 and 6 (longest ones) have a habit of developing a high
resistance causing a crossfire situation, most common symptom is a
miss under light acceleration at about 45 to 50 mph."

I replaced the wires a few days ago, been out on the highway today and
no more "jerking" problem. Also the recent hesitation on cold starts
disappeared too so obviously related. Feels like it has a bit more pep
too (although that may be my imagination.)

 

I had to go for an emissions test and my 93 GC 3.3 with over 300,000k on
it failed, took it to someone I could trust and it had no codes in it
but he did notice that the readings on the O2 sensor where low, the
voltages where to low and not changing enough.
Off to crappy tire for a bosch and we put it in and off for a new test
and it now passed with flying colour's.

Again this sensor did not post any codes as to it not working.

What is wrong with the bosch units?

REMOVE the NOCRAP in my address to reply.

 

(Rod Corkum) wrote in message
PROBLEM SOLVED!!

The first responder sent me a direct email: "The spark plug wires on
cylinders 3 and 6 (longest ones) have a habit of developing a high
resistance causing a crossfire situation, most common symptom is a
miss under light acceleration at about 45 to 50 mph."

I replaced the wires, been out on the highway and no more "jerking"
problem. Also the recent hesitation on cold starts disappeared too so
obviously related. Feels like it has a bit more pep too .