Playing with TPS
 

Well I've tried adjusted my TPS in both directions but after 3 starts/trips the ECU detects the change and compensates. The result is the car behaves exactly as it did before the adjustment.

My question is the following: Who else has changed the position of the TPS, what did it change on your car and did the changes stay?

p.s. I guess that's 3 questions

I've adjusted mine - same results with learning but you can make it go into power mode easier by adjusting it one way. I can't remember which - it was a while ago.

Actually I've found that I can get power mode just as easily regardless of adjustment. I've adjusted just about to the limits both ways.

I've adjusted mine, I do not see TCU compensating (but I've got one of the very earliest 92 cars), ECU does compensate and idle revs eventually become normal.

If I rotate it counter-clock wise (lesser voltage), 1-2 shift becomes smoother, but 2-3 shift with little throttle produces rev surge.

If I rotate it clock wise, 1-2 shift becomes very quick and jerky,
2-3 shift surge disappears. Downshifts become noticeable when gradually braking coming to a stop. The same effects happen if I do not rotate TPS, but simply drive at altitudes ~ 6000 feet. (Less oxygen in the air, more throttle required, ECU compensates because it has atmospheric pressure sensor, TCU does not - no pressure sensor and no information link from ECU).

Before you asked - mine is still a car, not an airplane :-)

i gave up on mine and ordered a new TPS. :mad:
according to the resistance measurements i'm getting, the car shouldn't even be driveable! it drives just slightly "weird". hopefully a new TPS, and a good cleaning of the IAC valve will have it driving like a new one again.

In my initial post I did mean ECU and not TCU (edited).

So if I wanted to set the TPS properly what is the exact resistance at idle? I may play around with more settings though.

While not exactly answering your question, i.e., resistance at idle, here's the simplest method I've seen - with thanks to Trevor:)

http://www.subaru-svx.net/forum/show...&threadid=8918

Yep, 0.5 volts is exactly where I ended with mine.

The best way to measure it is to insert a small thin wire into the middle contact of harness connector and put the connector back on TPS. I think I still have the wire hanging out there.

Since the total voltage supplied to TPS is 5.0 volts, you could, in theory, measure the total resistance between end pins and then adjust TPS to 10% of the total resistance between the middle and one of the end pins. The only problem is to get the ohmmeter leads in there.

Well have a look at the link above to Trevor's post.

I recently did mine using the pins through wires system that Trevor advocates. Worked very well. First I checked the voltage of the centre wire of the old TPS. It was 0.48 volts. The resistance across the two end wires, red and black, was 4800 ohms.

I put in the new TPS, set the voltage at 0.50 by rotating the position, and tightened up. The resistance across the new potentiometer was the same, c.4800 ohms, so I set sail.

Gear changes are a lot better, very smooth, and for a set throttle opening, it will tend to hold 2000 rpm, and the speed seems to wind up by magic as it seamlessly changes up, and uses the TC as a multiplier.

However, I still have a problem. It sometimes revs up to 5000 or more RPM when charging away from a junction. No rapid forward thrust, just revs, I ease off, it catches a gear, up around 60 it's like there never was a problem.

Any ideas??

You would think it was the 2-3 flare, maybe it is. But put it manually in 2, give it welly, and it goes rapidly with no slippage, no high revs, then ease off, and you get engine braking, just like a manual gear. So I feel it is not ratio 2 slipping

Any help much appreciated.

Joe

Just a quick heads-up on a couple items. Almost every car is the same when adjusting the TPS. If it has three wires, generally the center wire is the signal wire. Backprobe that center wire ('backprobe' means slide a pin or similar alongside the wire and into the back of the connector - piercing automotive electronic wires is a serious no-no, corrosion/resistance build-up), and connect a good digital voltmeter. Key on, engine off with throttle at rest, adjust the TPS to .5v DC +/- .1v. Using resistance to adjust the TPS can occasionally screw you up. I learned my lesson... ;)

Well, if you're right about this Beav, because I haven't backprobed the TPS socket, I've buggered it.:rolleyes: :D

What do you think of my problem above?? I was really hoping the new TPS would solve that one. The tranny was rebuilt last December, oil is not smelly or burnt [although I am about to get it replaced as a matter of course, for peace of mind], and the big rev-up only seems to happen a lot in D when I try to rev away from slow speed in 4. It will also happen from a standing start in a hurry though.

Slipping band on 2 & 4??

Joe:confused: :confused:

Your results with the TPS may vary. :D

It just plain wore out.

Joe, I just use a dab of silicone sealer on the puncture wounds I find on customer's cars. I wish I could be of more help with your tranny issue, but besides it not being my forte, my back has been aching to the point where I can't concentrate on much. If something pops to mind I'll post back.

Thanks Beav, will do.

How have you been, haven't seen you post for a while?

Back giving you trouble? Or is it the weight of the mortgage for the new house?:D I am assuming you must be installed by now.

Keep well,

Joe:)

Usually I do pretty well, it's just the past couple days that I've had some sort of spasm under my right ribs. The docs keep running up the tests for everything, but I always come out on top. :)

Yes, I've left the life of idle times and become a homeowner once again. Fortunately, I'm the creator and editor of my own to-do list. ;) Unfortunately, I find something new to accomplish each time I turn around... I'm beginning to feel as though I'm my own man AND my own woman at the same time. ;) :D