Engine/Transmission (1994 - 1998) Auto shifting problems

[sadams]

I have seen numerous treads on problems with shifting and the TPS sensor, and now it appears to be hitting my truck. When I'm climbing a hill and light on the pedal, at around 35-40 mph, (OD off) the TC keeps kicking in and out. I had a friend pull the TPS sensor off and check it, he just used an air hose and blew the "dust" out then put it back on (we had no contact cleaner handy at that time), plus he separated the wires out of the bundle and wrapped them in case it was a voltage problem, but now its doing it more than ever. Seems the cold affects it more. I called the dealer and its $197 for a new one. Any more suggestions before I go for new sensor? Should I try the contact cleaner first, or just fork out the $197? (I did have the throttle cable recall done on it last year so I know that isn't the problem). Will it hurt my trans. driving it while it does this?

 

[shendren]

it's noise in your harness going to the tps. DO NOT buy a new one. buy a rewire kit.



scott

-- email address removed --

 

[ndurbin]

I would try it agian and use the contact cleaner (it's $3 @ O'riellys if I remember). And seeing as you have pulled the wires out of the loom, if the contact cleaner doesn't work theres not much else can be done but replacing the TPS. $197 is not a bad price, cost about $220 the last time I priced one from a dealership.



Oh I just remember you ran use a round file and enlarge (oblong) the two holes the bolts go threw to hold the TPS and this allows it to move alil for adjustment.

 

[shendren]

did you pull them out all of the way? that's a tough one. i doubt it can be done. if you pulled them out just a little, then that's not enough. you need to completely rewire it.



look here... .....



https://www.turbodieselregister.com/forums/showthread.php?threadid=88462

 

[sadams]

We pulled the wires out for only about a foot or so where they come out of another junction/bundle of wires. Checking it last night, I noticed a problem with the pedal and throttle. I know it was better when I had the recall throttle cable fixed last summer, seemed it was working okay after that until this winter. Now I also notice the pedal sticks when I push the throttle down at about the 1/2 way position and I have to really push hard then it "snaps" past whatever is catching. Is it possible the throttle cable could be causing the problem? If its slipping in and out going up the canyon and I push harder and hold it, it stops the in/out thing. Unfortunately, I can't run everyone off the road just to keep it from "slipping" in and out.

 

[shendren]

rewire the tps.

 

[Taz]

I had the same exact problem. What I did was take the TPS off and take a dremel tool and bit and open up the TPS where I could get to the rotary resistor. I then took contact cleaner and ear schwabs and cleaned the contact area. All fixed now, runs fine, and has been running for a good 8 to 10 months with no problems.

 

[Joe G.]

sadams,



There is a natural "over center" hard spot in the throttle. It's in the pump. Especially noticiable with the engine off. The higher the RPM the higher the over center spot is. Something to do with the way the governor works. You may have stiff dirty linkage which makes it worse. Use some brake cleaner on the ball endings of the throttle rod. Then give them a good shot of lubricant. Note the WD40 is NOT a lube, it is water displacment stuff and will evaporate after a while. I like LPS #2 for lubing things like throttle linkage. I give my linkage a squirt of the stuff every oil change.

 

[mistered]

Don't blow your money before you know what's wrong! Other probable causes are the brake switch, transmission temp sensor, cruise control or anything electrical. Every 12-18 months I have had a TPS related problem and it's never been the same reason twice. The most perplexing one was when the SHAFT that rotates the rheostat insde the TPS switch wore out. It would work fine the first half of throttle postion then start slipping. Thing is, when everybody was testing it with the scan tool it would show up fine. Out on the road with an actual load and resistance on the throttle linkage is where the shaft would start to slip. I took it to different dealers, transmission shops, anyone that said they could fix it. I finally found this one shop that took it on as a challange. It took over two weeks but they had one guy sharp enough that did more than hook up a scan tool and follow the manual by route. Good luck.

 

[JohnE]

Check and see if the brake light switch needs adjustment. A hair trigger switch will also cause the TC to unlock, lock, unlock, lock (you get the picture).

You can usually troubleshoot this by noticing the cruise control trips off without command.

 

[Howard Durand]

Before doing too much, you should probably check the throttle cable installation and adjustments.

Just because the dealer did the recall doesn't mean they took the time to get the adjustments right. In fact, it is more likely that they didn't.



If you think the TPS is erratic, be aware that, in the 96 and later vehicles, the wire feeding 5 volts to the TPS also feeds the engine speed sensor.

Separating them and feeding the TPS with a separate, shielded wire tends to eliminate induced voltages from adjacent wiring.

Shendren's kit will help you accomplish that without a lot of research and eliminates the need for pulling all of the wires out of the loom.

 

[sadams]

I ordered the re-wire kit from SHrenden and am going to try that first as it seems like an easy, inexpensive way to get started. I'm hoping I'm lucky and hit the fix on the first try, we'll see when it gets here. Mean while, I driving the truck as little as possible as it drives me "nuts" kicking in and out all the way up the canyon and I don't know if this will cause any damage to the trans. Thanks for all the advise as I have something to fall back on if this fix doesn't do it but I have "great confidence" its going to work!

 

[Extreme1]

The brake light switch adjustment is actually faster and cheaper. Push the pedal down, grab the plunger on the switch with your fingers and pull it out. It will ratchet out and then "adjust" when you release the pedal. No tools required!

 

[shendren]

it's cheaper and faster IF that's the problem. in most cases it's not.