LT1 throttle position sensor

Guys, when reinstalling the TPS, do you need to wind it on in some way?

The reason I ask is that looking at the position of the tangs and the position of the lever on the throttle body, it looks to me like if you just stick it straight on it'll never engage and rotate.

You can't rotate the body of the TPS to any degree because there's the PCV pipe fitting in the way. The FSM just says to make sure the tangs line up with the lever. Very unhelpful there.

Wow, nobody's changed these things? I must be lucky.

I thought I'd be clever and wind the thing with a pick, which I eventually managed to do through a great deal of frustration only to find that the sensor was either defective out of the box, or was broken by my installation. Code 22.

I have a suspicion I screwed it up- that the sensor may be "clocked and locked" at the factory and that once installed you can actuate the throttle releasing the lock so it works. It's just not possible to rotate it into position from it's 'home' setting with those three pipe fittings in the way.

There's no youtube videos, the FSM and Haynes say nothing interesting about it, so I must have botched something. Well that's $35 down the drain anyway.

Sorry I'm late... I just unbolted the old one and bolted on the new one and was done.

A brand new one, I assume?

straight R&R. I usually check it with a voltmeter afterwards to ensure 0 and 100% throttle are accurate.

Ok, I'll update this when I get another new one. I suspect a new unit is pre-set and I jacked it up when I put it in.

Ok. Verified. A brand new unit has its position locked so that it can be installed. Once actuated, the sensor cannot (easily) be reinstalled if removed.

It would really have been nice if something in the FSM or Haynes manual had mentioned this.

So if you're reading this, when you get your new TPS be very careful when handling it. Don't forget the rubber donut. Install it carefully making sure to line it up correctly so the tang gets pushed in the right direction. You can see on the old one where the pushing action is happening. Install it carefully, I would then test it with an ohmmeter to make sure you get a reading off of it, then fully open the throttle and make sure the resistance changes between the center pin and one of the others.

New unit on left, old unit on right. Note the relative home position of each sensor is different.

[You must be registered and logged in to see this image.]

lamune wrote:

It would really have been nice if something in the FSM or Haynes manual had mentioned this.

Don't take this the wrong way, but it doesn't mention it because it's pretty obvious for the intended users of the FSM. Hopefully someone can benefit from this, and you were able to bring back your defective TPS.

Yep, I totally get that. And if you R&R without even paying attention you'd have no problems, but I'm far too curious for my own good almost all of the time.

Generally speaking a manual like this will call out things that can't be reused, whether it's seals or bolts or washers, etc. Seems kind of odd to me to not call out that the TPS cannot be re-installed, and is essentially destroyed upon removal. Pretty glaring omission if you ask me.

lamune wrote:

but I'm far too curious for my own good almost all of time

Entertaining to read about you 'fixing' things,..

you usually get it right by the 2nd try,.

Nick,something told me you would make an appearance on this thread.

It's not just a car, it's a learning experience.

lamune wrote:

Generally speaking a manual like this will call out things that can't be reused, whether it's seals or bolts or washers, etc. Seems kind of odd to me to not call out that the TPS cannot be re-installed, and is essentially destroyed upon removal. Pretty glaring omission if you ask me.

Enough already. They are absolutely reusable.

It's unfortunate that reinstalling the TPS is giving you trouble, but to make the blanket statement they cannot be re-installed is not even remotely accurate.

I remove & replace them all the time, you just slide them over the shaft and then rotate the housing to align the bolt holes.

I'm at a loss as to why someone talented enough to recognize the need, then select and install a DIP inverter (including what appears to be a voltage dividing resistor and tying unused inputs to ground) into a electrochromic mirror housing has so much trouble with inserting and aligning a throttle position sensor.

- J

Hah! you make a persuasive argument. I could very well be mistaken.

Well, in any case I shouldn't make blanket statements. I have only one example to go by, and in my example there was no obvious way to reinstall the sensor once it's been tripped from what I'll call "storage position". It's entirely possible in other model years and component arrangements that reinstalling is trivial. I saw F-body YouTubers adjusting their TPSes with no difficultly, but their throttle body plumbing arrangement may be slightly different.

The three fittings on the throttle body - PCV, evap purge, and water- all extend out beyond the plane of the TPS. I couldn't get enough rotation on the tripped sensor to engage the tangs onto the shaft with those fittings in the way. If you can in your case, awesome. I tried. And tried. I couldn't get it lined up. In the storage position, the TPS goes straight on with no problems. I just dicked around with it to pre-test it not knowing it was locked in a special way, and that was dumb on my part. You can see from the pictures that the home position of new and used sensors is quite different- way more than the 5 or 6 degrees I could get before the sensor body is stopped by a pipe fitting.

Anyway, these may explain my case better than words. If there's another way, I'd be very happy to see it, it may save someone else some money.

[You must be registered and logged in to see this image.]

perhaps if you open the throttle with your other hand??

Opening the throttle turns the shaft the wrong way. If there's a way to go past the closed stop and turn the plates the other direction, that would work. Maybe that's a method Jay is talking about. I didn't want to attempt it.

K,... lets go back to square one,...

why you changing the tps??



Have you messed around with the throttle stop?

If you remove the intake boot,. can you see if the throttle blades are closing all the way?

Or has "someone" bent the throttle to stay open slightly more at idle?

"Somebody" might have given it more opening,.to cover up a different problem,. i.e stalling,.?

Oh, Nick, I already changed it, I'm just speculating as to how you could get a used sensor back on. I didn't touch the throttle stop, that seems like a bad idea to me.

As for the reason - I have a problem with the engine hesitating/stumbling from idle and the "chuggling" issue as the FSM calls it. The troubleshooting charts for both issues point to TPS and MAP issues as likely common causes for both issues, so I changed both.

I don't know if it solved the problem yet or not.