Tps sensor!!!

[cp2295]

So I tried adjusting the thing with a voltmeter, got it .998 v at idle. But I kinda screwed up. I didn't know what I was doing and started touching random probes from the tps to its connector.. Finally I plugged in the tps connector into the sensor and stabbed the positive with a needle and got it to show my desired volts. Turned the truck on and now it's idling super high and when I let off the gas it goes up to like 2500.

So replaced the sensor and it's still doing it.. Did I totally screw up everything? Did I fry my computer?

It's showing p1506 idle speed too high

 

[Rearanger]

Why did you want to adjust the TPS in the first place?

 

[RonD]

No, you didn't fry the computer.

.9volts with throttle closed is correct, 4.9volts with throttle wide open is correct.
You do this test with key on engine off, and TPS connected.
Yes stabbing wire with needle is also correct, that is how to test "live" wires.

What you might have done was to tell the computer to "learn" a new TPS setting.

After working on any sensor, or pretty much any work on the engine at all, you need to tell the computer to "have a look" at any changes.
You can do that with a scanner/reader, via the reboot, or even easier, unhook negative battery terminal for 5 minutes then reconnect it, this reboots computer as well and it will then relearn sensor settings.
If you own any kind of computer you know that reboots are needed, lol.

Also check to make sure you haven't disconnected any vacuum lines while working on the engine, high idle could mean open vacuum.

When first started engine rpm should go up to 1,500, then it should go down to 1,000 if engine is cold or 750 if engine is warm.
The high idle at startup is the computer testing the IAC valve(idle air control), computer opens this valve all the way(big vacuum leak ) then closes it slowly to set idle according to ECT sensor(engine coolant temp) data, cold or warm.

 

[cp2295]

Well instead of dropping down to 750 like normal it dropped to 1100 once fully warmed up so I just said screw this and I changed the screw back to where it was and it seems to have worked

Before it was at .7 volts so I just brought it around there, maybe my butterfly valve is worn out so it is getting a lot more air at .9v as opposed to what it should be getting

 

[cp2295]

And I unhooked the battery for 20 mins after changing its setting

 

[Froggmann]

I had the same issue with my truck. It seems anything over .9v causes idle issues and revving between gears. Adjusting the TPS works great on Mustangs, on these trucks it's an item best left alone.

 

[cp2295]

Yeah I just brought the screw to just barely move the throttle

 

[RonD]

Well instead of dropping down to 750 like normal it dropped to 1100 once fully warmed up so I just said screw this and I changed the screw back to where it was and it seems to have worked

Before it was at .7 volts so I just brought it around there, maybe my butterfly valve is worn out so it is getting a lot more air at .9v as opposed to what it should be getting

This wasn't mentioned in the first post????

You don't use the throttle stop adjustment screw to set TPS voltage

You start already warm engine, then unplug IAC valve, idle should drop down to approx. 500-600 rpm, adjust throttle stop screw in or out to get that rpm range.
So if engine stalls when you unplug IAC adjust screw to open throttle a bit more and restart.

After you have that range the stop screw is adjusted.
Plug IAC back in and idle should go back up to 750rpm.
It is basically an anti-stall screw in case IAC valve fails.

TPS sensor should be below 1 volt with throttle plate closed and above 4.5volts with throttle plate wide open.
And as you slowly open the throttle plate the voltage should slowly go up, no jumping around, nice steady increase in voltage to wide open throttle.
Older TPS sensors had two screws on their case so you could rotate them slightly to set voltage, so you were not moving the throttle plate, you were moving the contacts inside the TPS.
This was similar to the old choke adjustment on a carb setup.

.9v and 4.9v are perfect ranges with calibrated volt meter and brand new wiring.
Computer doesn't care about that, it learns new low and high range as TPS gets older.

 

[cp2295]

Hmm well with the iac unplugged and taking the screw all the way off the throttle my truck doesn't die. It's probably at 650-700 rpms by listening to it.

 

[RonD]

Make sure throttle cable and/or, if so equipped, Cruise control cable are not holding throttle open a bit.
So engine off, open throttle pop off the cables and retest for low idle.

Although 650 should be fine, you just want it so the computer/IAC valve is setting the idle level, not the screw, or over tight cable.

There is a "cable mod" to shorten a stretched throttle cable, some take up the slack to far, lol.

 

[cp2295]

Yeah don't you use zip ties? Anyways I'll try removing the cable and giving it a go again, should my truck die if the screw isn't touching it?

 

[RonD]

Depends on how much air is getting in.

On an older engine I am sure there are a few air leaks.

The screw manually adjusts the air being let passed the throttle plate, so same as IAC valve but not a "controlled" air leak.
If you close off the throttle plate completely then engine will die if there is no other air source.
If throttle can't close all the way or can seal all the way then engine will not die.

That is an old way of checking for vacuum leaks, you would cup your hand over the intake and slowly close it off, and listen for the vacuum leak or the engine to stall

 

[cp2295]

I got a smoke test done and I have no leaks (according to the smoke test) but I got a lot of slack in the throttle cable, but the pedal Is pretty responsive. Engine doesn't die though when I back the throttle screw off and unplug the iac valve. I don't think the throttle plate is worn but I'll double check it closer. Maybe my iac is stuck open but my idle is alright and I have a new iac valve