Hi guys,

Last week I had to adjust my tps as it was only reading 0.15 volts at idle (was a new tps so had to elongate the screw holes)

I set it to 0.53 at idle and did the relearn on the PCM. For a day it worked fine -transmission shifted lovely and at the right times and the TCC locked up as it should. The next day without having touched anything the shifts became delayed and the TCC stopped engaging. Checked the tps voltage which was as i left it - 0.53v. Did the relearn again and everything was back to normal.

The problem is that it's doing this every day now - one day it shifts fine after the relearn and then overnight it seemingly goes bad.

Why would this happen?

 

Have you had your throttle body ported? If the back stop was ground down too far it can throw everything out of whack. If that is the case you would need to drill and tap the back stop and install a set screw so you can be sure it doesn't open too far. If it goes over 4.7 volts it will cause issues. 4.6 at WOT is as high as you'd want to take it. Hope this helps.

Lonnie

 

The throttle body is a UMI 92mm throttle body coupled to a FAST 92 mm intake manifold. As far as I know it is not ported. at WOT the voltage from the TPS is showing around 4.38 volts when the throttle is fully opened against the back stop.


The delayed shifting and lack of TCC isn't really apparent at WOT, more on gentle driving and highway speeds when the TCC should lock. When I finally think its sorted and the car is behaving normally, it all goes wrong again the next time I start it up the next day.


Car is a 2001 Trans Am WS6 by the way.

 

Buy oem sensors, not china junk.

 

Not sure what TPS I have it was from a UK supplier. No marking on it.

Would a dodgy quality tps cause the PCM to constantly alter its perceived zero percent voltage?

 

Yes, they are **** right out of the box.

 

I've now ordered an ACDelco professional range TPS from rock auto. should be here in the UK within 10 days.

Is it totally necessary to elongate the holes and set the voltage on a new sensor?

how come they don't come with that facility?

Hope this fixes the fault but if not ill be at a loss as what to do next.

 

You shouldn't have to. Do a TPS reset on the pcm and it will relearn the new sensor.

 

Thanks again. I'll report back once it arrives and it's fitted.

 

My new AC Delco professional range TPS came yesterday and I've fitted it this morning. I'm still having the same/similar issue. First drive out the TCC acted as expected and was locking up above 45mph in 3rd and OD. After stopping, turning off and then coming back to the car and starting driving again the TCC didn't engage at all apart from being on the motorway at 70mph plus. The voltage remains at 0.53 volts on the signal wire at idle.

Can't understand why it always performs as expected the first drive after doing the TPS relearn but after that it seems to stop working. :-(

 

Also, probably worth noting that with my original TPS, the lockup at highway speeds was very noticeable but when it was locking up this afternoon on the motorway I didn't actually notice that it had locked up - it must have locked up ever so gently rather than the usual 300 ish drop in rpm.

 

Anybody? I'm at a loss.

 

Well I've found something !

The brand new TPS has broken damn it! The return spring has pinged off inside and is rattling around, the plastic which surrounds the throttle shaft falls out in my hand and when you press it back in the potentiometer output is all over the place. Another new one on order.

 

I had a similar issue. One of the pins in the connector going into the TPS had pulled out slightly. After 3 new sensors, The wire popped out of the connector when plugging it in.

 

Can't believe this will be the third one I've had!

If this doesn't fix it then I will be out of ideas.

Hard to believe the AC Delco pro one failed within 3 days

 

If the new tps doesnt fix it, something could be going on with the vss (speed sensor) in some way causing the vcm to get confused. The shifts and tcc lock up are speed related as well. Just a thought.

 

Had considered this, although my speedo is working spot on. I'm saving for HP Tuners at the min cos I'm gonna get no where without it! Just costs about £500 delivered to the uk with taxes etc so will be a couple of months before I can buy it

 

New TPS came and fitted.

Now no lock up at all.

Relearn procedure done. No SES.

Wish I'd never touched the TPS at all now as it was working fine with the original TPS (original one was giving me 7.5% at idle so transmission went hard into drive which is why I changed it. Since then it's not worked properly)

 

Just had a thought - does the PCM have a number of drive cycles to complete before any codes will age out?

 

The shift solenoid and tcc solenoid could be on the fritz as well.. they are pretty easy to replace and not very expensive.

Also if you have the old tps, try and put it back in the way it was and see what happens. Were you having problems before you changed it?