TPS. Dial in the voltage or leave well enough alone?

[any4xx]

‘95 Sierra K1500.

My drivability issues are all ironed out so now I’m in the tinkering phase. Today I checked the voltage coming out of my TPS. .8v with the throttle closed. After confirming that the voltage climbs appropriately with throttle actuation I decided to slot the TPS mounting screw holes a bit to see if I could get it closer to .5v at idle. I managed to get it down to .47v but the truck idled horribly. I was up against the clock so instead of disconnecting the battery to clear the computer I just rolled the TPS back up to its “stock” position and drove it away.

But NOW I’m wondering if I shouldn’t roll it back to read the proper idle voltage and let the computer relearn or just leave it at the .8v position.

What say ye expert types? Get it on the money or just be happy the truck is running well?

 

[PlayingWithTBI]

Get it on the money or just be happy the truck is running well?

Personally, I'd dial it in, what voltage do you see with it WOT? It s/b ~4.5

 

[any4xx]

Personally, I'd dial it in, what voltage do you see with it WOT? It s/b ~4.5

I don’t remember the exact number but it was over 4.5v.

 

[PlayingWithTBI]

I don’t remember the exact number but it was over 4.5v.

OK, at least you have full range on it. I'd still adjust it. When it's reading too high the 'puter won't think you're at idle when you're there. Your high voltage will come down a little too.

 

[evilunclegrimace]

I would second the adjusting of the TPS, after you get it down to around.5V try adjusting the throttle plates and see if it likes it.

 

[PlayingWithTBI]

after you get it down to around.5V try adjusting the throttle plates and see if it likes it.

^^^this AND, watch your IAC steps. You want it ~10+ when fully warm and without A/C running.

 

[any4xx]

^^^this AND, watch your IAC steps. You want it ~10+ when fully warm and without A/C running.

Unfortunately I do not have an OBD-1 scanner so I’ll not know what the IAC motor is up to.

 

[Schurkey]

If you adjust the TPS to reduce the voltage to what you want it to be, and THEN you screw with the base idle screw...


...don't you have to go back and re-adjust the TPS to put the voltage back where you want it after you've changed the idle throttle shaft position?

Screwing with sensors and not having a scan tool is time consuming and leads to errors. You'd do well to invest in the scan tool before you start spending time on the sensor and idle speed adjustments.

 

[any4xx]

Yeah… I’m striking out on finding a “real” OBD-1 scanner. I’ve got an older Windows laptop sitting around so it’s time to buy the cheap cable and download the diagnostic software to see if I can make that sing. Many years ago I tried a similar system and never could get it to work properly and I’ve still got that prejudice in my head.

 

[Pinger]

Yeah… I’m striking out on finding a “real” OBD-1 scanner. I’ve got an older Windows laptop sitting around so it’s time to buy the cheap cable and download the diagnostic software to see if I can make that sing.

Many years ago I tried a similar system and never could get it to work properly and I’ve still got that prejudice in my head.

Is that the knock-off Delphi system?