Engine/Transmission (1994 - 1998) TPS Puzzle

[DMcClenaghan]

The monkey-motion throttle linkage adjustment on my '96 automatic is correct according to the service manual, however there is still some ways to go before I get WOT on the injector pump. If I adjust the linkage to give me full travel, the TPS measurement is wrong. I think I'd rather have full throttle available, but what would the incorrect TPS adjustment screw up?

Thanks!

 

[WBusa]

It will screw up your transmission's shift points plus its determination to stay in the right gear. An old TPS gets outta whack and DC says you have to replace it (at huge cost), but 99% of the time can be rescued either via a good cleaning or, if that doesn't work, by ovalling its mounting holes to enable you to give it a slight twist until it is back to outputting the correct voltage. I've lost track of the link to the published procedure for doing this... can someone jump in here?

 

[Joe G.]

There is a better way to adjust the TPS. Get hold of Howard Durand for the details.

 

[tp0d]

Best way to do it is to take off the entire TPS, get some RadioShak TV Tuner cleaner, and hose it out a few times. Let it dry, then pack the switch opening with dielectric grease. Reinstall, and should be fine for quite a while.



You can also take a small rat tailed file, or a round drywall saw (as I did), and egg-shape the holes so the TPS will turn counterclockwise. This will allow some adjustment in voltage output for the tps. Best way to check voltage is to carefully slide a thin needle thru the wire. I`m not sure which is power, ground or output.



good luck



-j

 

[Joe G.]

The rat tail file is not necessary. Nor is rotating the TPS. Cleaning it is very important. I had a bright idea about how to make it adjustable. Howard got it to work.

 

[Dave Remillard]

Joe G. Care to elaborate a little more on your bright idea. My curiousity juices are flowing.

 

[Joe G.]

I was discussing the TPS adjustment process with Howard. I suggested to install a pot in the ground wire from the TPS connector. Howard liked the idea and got it to work. I'm not sure what value pot he used. He has also rigged a mount for it. In the stock position with the pot adjusted to minimum resistance he has . 5 volts on the TPS signal wire just like I do. By turning the pot he can get more than 2 volts. So I hesitate to recommend doing that until you can get the information from Howard.

 

[Howard Durand]

Joe, you are selling yourself a little short here. It is your idea and a good one.



Bill Kondolay at DTT suggests setting the signal voltage on the TPS to 1. 2 volts in idle position. My stock TPS only produces about 0. 5 volts at idle and you have to remove a lot of the TPS housing to get it to turn enough to get 1. 2 volts. I practically destroyed one in doing that. It does the job but is a lot more work than necessary.

Joe's idea of putting a resistor in the TPS ground lead is much simpler and requires no modification of the TPS housing. All you have to do is cut the wire that that runs between the TPS and ground and put a resistor in series with it.

I used a 1000 ohm, 5 turn precision potentiometer for mine to give a little more control over the adjustment. It has a locking knob on it so it can't move once it is set where I want it.

It actually only takes between 200 and 500 ohms to get the right voltage and most any type of potentiometer can be used.

Mine is set at 1. 2 volts right now and I am happy with it. The DTT torque converter will stay locked now when the throttle is lifted and remains so all the way down to about 1200 rpm.

With the voltage much less than 1. 2 the TC drops out of lockup normally when the throttle is lifted.



A simple 0 to 500 ohm potentiometer will work fine.

Connect the wire coming from the TPS to one end of the potentiometer. Connect the other end of the potentiometer to the wire that goes to ground. Jumper between the grounded end of the potentiometer and the wiper.

With the wiper turned so it is at the TPS end of the resistance, the TPS will be the same as stock. As you turn the wiper toward the grounded end, the signal voltage will rise.

 

[Dave Remillard]

That is a great idea. My one concern would be keeping the pot clean. However if it is an open face pot, that should be very easy to do. Some contact cleaner and your done. Just wondering where you mounted yours Howard?

 

[Howard Durand]

Here is a picture of my pot assembly. It is mounted in one of the threaded end caps screwed onto a short 3/4" PVC nipple. The wires poke out through a small hole in the other end cap.

The two wire cable is long enough to follow the wiring harness from the TPS back to the firewall then up and over to the bracket where my Prime Loc has been relocated.

It adds about 6 or 8 feet of wire into the ground circuit for the TPS but doesn't appear to have any effect on performance.

The pot that I am using is real easy to turn so I put a locking type knob on it. (not shown in the picture)

With a little RTV silicone the assembly could be made water proof so it could be mounted most any place that is convenient.

It would also be real easy to run a three wire cable and clip one of them into the TPS signal wire so it would be readily available for voltage measurements.

I really don't like sticking paper clips into connectors or needles through wires if I don't have to. I didn't need to do it in my case as I have already tapped into the TPS signal at the PCM.

 

[WBusa]

Joe and Howard, that's a very nice idea. The only addition I can think of to suggest would be to find a plastic (i. e. , non-degradable) label of some sort to stick on the PVC body, with some indelible printing on it explaining what the heck it is and how to use it. The truck's next owner will thank you for it. I think such labels are a good idea for any non-commercial 'home-brew' mods. We may all intend to keep our trucks until they turn into rust, but "Life is what happens while you're busy making other plans. "

 

[Howard Durand]

WBusa, you are so right. I have thought about writing an addendum to my owner's manual describing the mods I have made to this truck.

As has been said before, "the road to hell is paved with good intentions" and that may well be where the new owner will have to write for the details if I continue to procrastinate.

 

[Joe G.]

Are you guys saying that a scribbled note in the top of my relay box is not enough to explain my mods? :-laf :-laf :-laf

 

[WBusa]

Hmmm... well, its better than nothing, Joe (but then, so is a poke in the eye with a sharp stick). An addendum to the owner's manual is better than nothing too, Howard, unless of course if the vehicle and the manual ever get separated, or if a mechanic simply doesn't think to look for it.



I've been thinking for a while about tagging my various mods for the benefit of whoever inherits this truck from me (such as "Dowel Pin Secured, 6/2004")... let's face it, these CTDs will outlive us all. And a tag on or near the mod is certainly the best way to go, since the poor sap staring at your mod will find the explanation right there. And I think I've just found the perfect medium to do it with:



http://www.labsafety.com/store/product_group.asp?dept_id=1797&cat_prefix=5WA



Blank Aluminum Labels and Tags

Create a lasting record by using any hard point to engrave information into surface. Long after ink would wear off, your message will still be readable.

Specifications: Aluminum foil Labels with adhesive backing stick to virtually any surface. 100/pkg. Double layer of aluminum laminated to tagboard gives you a durable, lightweight Tag that's oil-, solvent- and weather-resistant. Information remains legible even after painting, or in very dirty environments. Eyelets add tear-resistance. 25/pkg. 26-ga. galvanized Wires are 12 in. long (sold separately).



I found these at Lab Safety Supply, a company I've been doing business with for a few decades now, so I feel I can recommend them. Their catalog is a lot of fun.



I do believe I'm going to try this... .

 

[Joe G.]

Most of my mods are electrical so I don't think labels will work. I'm thinking of finding some software that will draw wiring diagrams and schematics. I have just finished building and testing an automatic pump controller for my aux tank. The service manual has wireing diagrams, connector pin layouts, part locations, connector locations, and splice locations. Plus a discussion of how something works. I have been thinking of creating something like that for my mods, electrical and mechanical (I'm starting to confuse myself). I'm going to build and install a TPS control like Howard built. It will go in my new relay box instead of an external mount. I could label my pump controller all I wanted to and very few people would even have a clue how it works so they could fix it if necessary. Labels would help for the KDP and things like that for sure.

 

[Howard Durand]

Joe, if you find a schematic drawing program, let me know. I have been using Adobe Photo Deluxe, a photoshop type program, to draw mine. It is too much trouble to draw zig zag lines for resistors so I just make small rectangles. True electronic symbols would be nice.

As for housing the potentiometer, there is any number of ways it can be done. Just make sure it can be kept dry.

Or, if adjustability is not required, a pot could be used to determine the exact resistance needed then replace it with a resistor of that value. That could be sealed with heat shrink tubing and RTV silicone.

Actually, any addendum I might write would be kept in a notebook that I keep in the truck where I record fuel purchased and mileage as well as any changes I make to the AFC star wheel and all service information.

 

[WBusa]

I'm thinking of finding some software that will draw wiring diagrams and schematics.

Joe, you might want to check out Visio ( http://office.microsoft.com/en-us/FX010857981033.aspx ). I've been using it for about a decade; best general-purpose technical drawing program out there - easy and very powerful. The 'standard' version, which is about $60, doesn't have all the nice electrical and mechanical engineering doodads that the 'professional' version ($130) has, but even with standard's basic 'block diagram' functions you can easily cobble together circuit schematics, etc... you just have more items to create yourself, and fewer drag-n-drop choices.



You can download a 30-day free trial of the standard version. I mostly use Visio to create accurate scale plans of woodworking, remodeling and landscaping projects, but (especially with the libraries the Pro version gives you) you can do just about any kind of technical drawing you can imagine. I always hate recommending a Microsoft product, but Visio is one that actually works (they acquired it from another company, of course).

 

[Joe G.]

I think there is some free stuff available. I was looking up what was involved in makeing a PC board with custom traces and found all kinds of free software for doing that. Not really worth the trouble to make a PC board for a one off thing, but it doesn't cost much. Anything that costs very much is not worth it for a few diagrams. I can do it with LViewPro if I have to. Better to have something that will make the symbols of course. Howard, if I find anything I will let you know. I may not get around to doing any searching for some time. Busy making up some genealogy packages for some newly discovered cousins.

 

[Dallass]

Potentiometer

Are you saying that if I put a potentiometer in series with the ground wire of the TPS and set the voltage at 1. 5 V I woudn'd need to use the mystery switch to lockup the TCC?. I had my transmission rebuild and put in a TransGo shift kit & Precision of NewHampton Diesel TC. The problem that I'm having is with the 1st and 2nd shift not working when pulling my 5th wheel. Had trouble when Dodge Boys replace the speed control senor and didn't replace the wire connecter back into the senor right. Would want to start in 3rd gear most of the time. Trans shop found the trouble and also replaced the governor solenoids. When I left this time with the 5th wheel, it would start off fine, but a few miles down the road I lost 1st gear. Had to put it in 2nd and shift up to drive for 3rd gear and overdrive. Shop scran said Gov Press sen CKT too high (P 1763) Also Gen Field not switching properly (P 0622) and trans volt relay CKT 0 or 5 (P 1765). I had the relay removed and jumper wire installed. They said voltage @ transmission w/key off not good for solenoids. They replaced the governor solenoid again, but said any more electrical problems are on me. So have not put the jumper wire back in. But if I can't lock up the TCC, my exhaust brake is of no use to me.

 

[Joe G.]

Could you tell us what year truck you have?