Need help! So far no one's been able to give me an answer, but maybe someone out there has had this problem. To start with, I have a Van Aaken pump controller. Truck has same problem whether it is plugged in or not. Driving down the road, easy going, truck begins to go either in and out of overdrive, or the torque converter is locking in and out. Can't tell which. Starts out a very subtle change for a second or two, then switches back. After a while it switches for longer periods. Sometimes does it a few times and then nothing for hundreds of miles. It gets worse as time goes by. The hotter the temp. the worse it is. Sometimes after the tranny shifts, the engine shuts down to an idle for a second, or sometimes I have to pull over and let it cool. When the trouble started, it was only while pulling our 5th wheel. Now does it even without a load. Any ideas?

 

Welcome aboard, update your sig so the more knowledgeable gys can see what your workin with, clean your battery cables and other groundind points and then try this. goodluck.
This procedure has shown to help 24 valve ISB engines. It is basically teaching the fly by wire accelerator on these trucks to reread the position of the pedal and it's limits. Most complaints this will help with is poor acceleration, improper shifting, bucking in 5 and 6 speeds. Has been known to increase fuel mileage in some instances.

1. Set parking brake
2. Disconnect negative battery cables on both batteries
3. Turn ignition key to run(to drain any remaining capacitors)
4. Let truck sit for 30 minutes( this is the recommended minimum)
5. Return ignition to OFF position
6. Reconnect both batteries and secure, not a timed event
7. Turn key to run position(not start) and depress accelerator pedal slowly all the way to the floor
8. Allow pedal to return to top position slowly
9. Turn ignition switch OFF
10.Release parking brake

 

Thanks for the suggestion. Will give it a try. We just bought this truck, and started having problems on our first trip out. Could this be the PCM going out?

 

No, the PCM is not a common problem on these trucks.

Do what was suggested above and if that doesn't solve your problem you will want to go here and follow the procedure. Please keep in mind that this procedure is an attempt to get your APPS (potentiometer) back into its operating range. If this does not work you will need a new APPS and they are $300+, but only take about five minutes to replace.

Let us know how you shake out.

 

Thanks. It is good to know that the PCM isn't the problem. We had a couple of "mechanics" look at it, and told us it could be the APPS but wouldn't say for sure.

 

I had kind of a similar issue not too long ago. Same symptoms anyway. Fixed it by wrapping the alternator wire to the battery with aluminum foil (thanks to Big Blue's advice). Serves as an electrical noise filter. You might give it a try, it's easy and cheap!

 

I would bet this an electrical noise problem. If cleaning the battery terminals causes it to go away it is only a temporary fix. There are several causes but cleaning ALL the grd points is the first step. Weak batteries is also a good possibility - optima red tops if you can afford them are good. You should also run a new grd wire from the PCM (the one on the firewall behind the airfilter) to the battery, the grd wire is on the lower centerside of the PCM. As suggested before, wrap the grd wire from the alternator with tinfoil. One of the best fixes is a noise filter from DTT, $40.

Good luck. Again - BATTERIES - if they are OEM or older than 2 years take a good look at them and don't just rely on a battery tester.

 

Thanks everyone for the tips. I've done everything suggested, and each step seems to make it better. It is 99 percent better, but still getting a little bit of errant shifting. Will try the aluminum foil next... What I thought was going to be a disaster is looking much better thanks to your help. THANK YOU!!