mxw128

I reinstalled my TPS to my 94 LT1 and got some codes. When I checked it out, the PCM wasn't seeing a good voltage from the TPS. I checked the sensor with it removed and powered and it provided the expected voltages. (I moved the sensor as I read the voltages)

The picture is of the back side of the TPS, the side that mates with the throttle tab and I marked (red in the pic) where the sensor "tangs" needed to be during IDLE and at WOT to get the right values. These do correspond to where the throttle tab is during idle and at WOT too... (the throttle tab is shown as the blue bar and this is the position at idle) The direction of rotation is shown too, so from idle, the throttle tab rotates counter clockwise in the pic to line up with the mark at almost 12 o'clock.

The problem is that since the sensor is spring loaded and returns to the position shown in the pic, simply bolting it up puts the throttle tab on the wrong side of the tangs. So directly bolting it on, the throttle tab does not turn the TPS at all... It's almost as if the sensor needs to be installed at 45 degrees then rotated into place and bolted up. This doesn't work because of interference with the Canister Purge nipple on the throttle body... This appears to be purely a mechanical problem Any ideas how to install the TPS?



**UPDATE**

OK, got the new sensor today, here's a pic:



Comparing the "tangs" with the old one, this one would be MUCh easier to install. Somehow the old one must have gotten shifted, and when I removed it returned to a position further back than where it started..... and the old sensor still was good, once you figure out how to get it installed...

mxw128

OK, I got it...

No matter what I did, the sensor would not install properly. Rotated all the way clockwise until it hit the canister purge nipple wasn't enough to get the throttle tab on the correct side of the tabs inside the sensor. I wonder if the tabs got distorted somehow and the new ones would have a taper of some sort. So I ordered a new one... while waiting for that one I took the old one (the sensor itself is still good) rotated it past the WOT position, held it there and drilled a small (like 5/64 small) through the plastic shoulder and into the cup where the throttle tab sits. I inserted a piece of wire to hold it there, installed it and then pulled the wire out allowing the sensor to snap back against the throttle tab. The hole is covered by the foam gasket and the hole will never actually line up in operation (it's past the WOT position)... works like a charm, car runs fine. I checked the voltages and all is well, and no more check engine or ASR lights.

Daredevil95

Seems like you had a hard time, when I replace my TPS, I had someone hold the TB linkage open a little bit and the TPS lines right up and insert the 2 screws. I've done it by myself a few times, holding the TB linkage open myself and install TPS/screws but, it's definitely easier to have someone hold open the linkage. Whatever works is good.

mxw128

My problem was though that holding it open only moved the tab further between the tangs inside the sensor, I would have needed to move the throttle " more closed" to help with this one. I'm curious to see if the new one is oriented differently...

Daredevil95

Yea, that doesn't seem right, usually the TB linkage is opened then slip in the TPS and close slightly until screws line up, I never seen a TPS install that went past the TB close position to line-up/install, I would agree that the sensor is not oriented correctly but, if your getting the correct voltage of around .4+ at closed TB position and 4.5+ at WOT then all is good but, it doesn't seem as though the sensor is oriented correctly.

mxw128

Yep, the sensor was off.. I updated the original post with a pic of the new one. What's strange is that the sensor won't rotate in that direction, so I don't know how it could have moved...

Daredevil95

that's good....easy fix!

mxw128

Did you do the tps relearn procedure? There was a paper with the new sensor saying its required but you need the Tech1 tool to do it...

Daredevil95

No, plugged it in, erased the code history and checked the parameters with my scanner and everything checked out ok at closed and WOT positions and the code never came back. I installed AC Delco unit.

1937Chevrolet

I see this is very old but in case this helps another user thats all good.
It would appear that you may have the wrong TPS, the correct part number is 17106681, the unit you show is possibly a 17106682 and is for a counter clockwise rotation and this is why you had much trouble getting it to install as it is technically working backwards in its rotation which may leed to issues in the near future.
This TPS unit 17106681 is a clockwise rotation and is typically suited to most applications and would slip into position with the throttle position at idle or there abouts.
Regards, Jeff.