Voyager: Very weak acceleration when cold

[amarshall]

I have a problem with my 1997 Plymouth Grand Voyager, which has defeated my local Chrysler dealer. Any suggestions would be very welcome!

The car has the following symptoms:
* The engine can be lumpy when it is first started in the morning, and it occasionally cuts out. This lumpiness usually clears after a few seconds.
* The acceleration is intermittently weak for the first ten minutes or so – it can be so bad that the car will not accelerate above 20mph.
The weak periods cut in and out suddenly. They usually occur when the engine is under load, such as when pulling away from a stationary start.
* The warning lights on the dashboard do not indicate any fault.
During the weak periods, the engine sounds a bit muffled. At really bad times (such as when the accelerator is fully down but the engine is hardly responding), the exhaust sometimes makes a spluttering noise.
* The engine will usually idle properly. Accelerating in neutral gear, to rev the engine, does not usually show up the problem – it only seems to occur under load.
* The car seems to run well after the first ten or fifteen minutes, once the engine is really warm. It may run well from cold, on occasions.
* The problem shows up on 60-80% of mornings. It shows up much less often in the evening.

The following work has already been done:
* The Chrysler dealers have attached their computers but found no fault.
* The spark plugs, ignition leads, distributor cap, rotor arm and temperature sensor have been replaced, but this did not resolve the problem.
* The dealer advised me that their next steps would involve trying lots of things, in the hope that they manage to replace the right component by accident. This will be expensive and may not resolve the problems. They advised me to find a specialist auto-electrician instead, who may be able to identify the fault.
* The auto-electrician who is looking at it needs more information about the internal wiring of the vehicle, such as pinouts for the ECU.

So I would gratefully receive any ideas about:
* What could be causing these problems.
* Where to find comprehensive wiring information.

Thank-you!

[1thunder]

from a shop manual possibly from a library

[amarshall]

Would a standard off-the-shelf manual, such as a Haynes manual, have enough detail in it for an auto-electrician? I would have thought he would have tried that, but you never know.

[harryliuusa]

I had a similarproblem in this past summer, it turned out a bad O2 sensor.

You may also try an oil cleaning product called ARX at www.auto-rx.com
It worked for m on engine and transmission.

[neon_rt]

One of the ideas I have is the vehicle speed sensor. At speeds under 9 mph the engine output is limited to prevent damage to the fragile transmissions these vans have. If the computer doesn't think the van is moving, it could limit the power and rpm. This would also show up to the driver because the Speedometer would not be working right either. Another idea a have a clogged Catalytic converter.
Warm it up, trade it off.

[amarshall]

Originally Posted by harryliuusa

I had a similarproblem in this past summer, it turned out a bad O2 sensor.

Interesting, thank-you. Could you please tell me whether your problem, like mine, only showed up when the engine was cold? The autoelectrician said that the symptoms sounded like an incorrect fuel mix (which presumably an O2 sensor would also cause), but he thought that the temperature sensor was to blame because it only happened when cold. Unfortunately, changing the temperature sensor did not fix it.

[harryliuusa]

My problem was a opposite, it had difficulty acclerating at hot summer...

You may also try warming the van while leaving at "N" instead of P. How cold is there? Coldness is definitely not a good thing for transmission gears.

[MT-2500]

You need to find another dealer or a good repair shop.
Either one should be able to find the problem.
Tip on going to the dealer
Ask that only a factory certified gasoline engine performance specialist work on your car.
Not all dealerships are concerned with how repairs are dispatched, and not all dealership techs bother to take advantage of the training offered by cry (the vast majority of which is paid training). If the dealer is uncooperative, ask for your money back and call around for a dealer that will accommodate you.

Check around Ask around
Word of mouth.
Family friends coworkers neighbors business people and delivery people.
Mailmen and parcel delivery people get around and notice a lot of stuff.
Even a good parts house knows what shops are good and not good.
Chamber of commerce and better business bureau and city hall.
If you find a good referral to a repair shop go look them over and talk to them.
Look for a clean looking busy place with nice people running it.
Ask a few questions and ask about their qualifications and training.
Not all places have trained tech/mechanics.
If they do not find a place that does.
Even all dealers do not have all trained techs/mechanics.

Here is a link to all data for wiring diagrams and all repair info on your car.

http://www.alldata.com/products/diy/index.html

MT