Geerhed

iTrader: (1)

I went to Wiking's excellent CarDomain page and read several of his write-ups on 3rd Gen systems (great information - I've lost the link but perhaps he'll post it again in this link).
His information on the TPS caught my eye because I've had an issue with my transmission bogging down in Overdrive and not kicking down when it should (causing the engine to stutter like a 5-speed in 5th gear at 15 MPH).
I removed the TPS, cleaned it (not for the faint of heart, and, in this case, not necessary), and upon re-installation noticed that the top screw hole was slotted -- AHA! So, I could finagle the switch slightly to fool the engine into thinking I was slightly more into the throttle, and possibly get it to kick down sooner?
BOY, was I right.
I rotated the TPS as far as I could clockwise(there's like 1/4" play, which equates to about 20% throttle), so that the TPS would show more throttle angle. Turns out this was WAY too much because it shifted like I was heading out of the pits at Daytona on Power setting. Good news is that, at this "extreme" angle, the tranny kicked down with very little throttle demand and the car was very responsive. Tranny shudder is gone. Downside is very hard shifts at light throttle, especially when cold.
Tomorrow AM, before I head out I intend to 'split the difference' on the rotation and see if I can zero in on the optimal setting. I like the ready tranny response, but dislike the hard shifts.
This adjustment can be made with a small (7 or 8mm) wrench and/or an offset phillips screwdriver. On the VG, the TPS is right on the top front of the engine, on the intake opposite the two throttle cables. Adjustments can be made very easily.
If you rotate the sensor the wrong way, it will take FOREVER to kick down and drive like Grandma's Buick (and I'm not talking about the Roadmaster with the LT-1).
Careful not to remove the bottom screw (although you'll need to loosen it to adjust) -- it's a biatch to replace.
If anyone knows of damaging effects of messing the the TPS, please let me know! I'm sure I'm messing with the fuel mileage, but my other car is a 98 Tahoe, 5.7L with a Whipple Supercharger, so anything over 20 is gravy to me.

Happy Motoring

internetautomar

iTrader: (30)

Have you been reading jeffs threads again?

Wiking

Nice to hear! Link is here again. Btw. How did u clean u TPS???

Adjusment:
TPS contains zero pos switch for engine idle ctrl. Adjustment should be done based only on that... Alas, stock TPS resistor is/was set up wrongly, starting from 2.5KOhm. I repositioned the plastic control to get in specs = 1KOhm at zero (VG).
see the pages:
http://www.cardomain.com/memberpage/748507/6


Hard shifts might be possible if u have not yet cleaned ALL tranny related connectors.
click to see: http://www.cardomain.com/memberpage/748507/15

.

Geerhed

iTrader: (1)

Removed the unit from the car, removed the cover (that was the most difficult part), hosed it with electronics cleaner, let it dry, cleaned it up, put a light coating of dielectric lubricant on the contacts.
There was very little wear and tear (my car has 175,000 miles), and the unit was in good shape.

Internetautomar: I don't know which of Jeff's threads your referring to, however, when I first made the comment about "Grandma's Buick", I remembered that there is a certain Wolf in Sheep's Clothing in the Buick line so I needed to account for that!
For those who don't know what I'm talking about: in the early 90's, one could order the Buick Roadmaster with the LT-1 (Corvette) engine option. The result is a Wednesday-Go-To-Bingo Blue-Hair car that will literally melt the rubber off the rear wheels.

Wiking

How was it: Was the original zero postion reading 2.5KOhm like my TPS was, did u check. If so, did u make any mods.

There is no way my TPS could have ever been inside the specs; just look at where the contacts have bee sliding. Wear is seen oly on 2.5-11KOhm resistor surface area.


click: http://www.cardomain.com/memberpage/748507/6

I am very interested; you're the very first commenting on this issue anywhere.

goon9

iTrader: (13)

so that sensor does nothing for 5-speeders?

Wiking

My experience is only for automatic: btw. Maxima Automatic super ! I encourage ALL to Swap into it....

The FSM tells these:
- TPS is used for engine ctrl while engine cold
- After warmup O2 'takes over', TPS not used but if O2 fails
- Autotranny TCU calculates gas pedal movement speed from this, gearchange results - IF.
- Gearlock is based also on TPS input
- kickdown sw not used (!)
- zero pos sw is used on WHAT? [FSM is really pearl harbour -shy on detailed info]

Geerhed

iTrader: (1)

I didn't check the resistance at the original setting -- just rotated it a bit and checked the results.
Mine was worn closer to the "1K Ohm" spot you showed on your pic. But, like yours, it can't be showing 1K Ohm's at idle. I've moved it now, so there's no way to tell what it was set at.
I moved it back 1/2 way between straight and fully rotated CW, seems to be shifting better, but still has good response. I may move it further back slightly after my commute home this afternoon, but I think I've about found the optimal spot.

Wiking

Thanks!

Its good to know that there are original TPS boxes on the market that are bad from the beginning (mine). That is mechanical impossibility that my TPS has fulfilled ever that 1k zero pos criteria. I had to melt and mod the plastic slider with my welder. Before that, its always been 2.5k as starting point... No wonder the gearbox was hysteric when I got the car. ...Bad quality management at factory...

Now I think its the best tranny I've ever driven - and been testing 'some'.