I purchased a new TPS but it came unadjustable for my 91 5.7 litter engine. As is, it measures 0.86 volts at idle. I keep reading about setting it to 0.54 at idle for earlier models.

Any ideas whether I should enlarge the mounting holes and adjust it or should I leave it as is as perhaps 90 and later model TPS are actually unadjustable? Thanks.

 

90 up nonadjustable me thinks

 

SD is unadjustable. The ECM reads it at closed and considers it zeroed.
No need to enlarge the holes.

 

That's good info to know. I've never messed with mine and it reads about .80V. The service manual says it's supposed to be below 1V closed and above 4V when wide open, that's it. I wondered where the .54V rule of thumb came from. I guess it's a MAF thing.

 

Ok. Obviously I was inexperienced enough to ask this question before AND I have enlarged the holes to set it to 0.54 as it was for pre-90. Basically, no matter how I set it, it would not have mattered as the ECM zeroes it when closed, you are saying.

So I have set it to .78 yesterday before I read your reply as I remembered its value being somewhere around 0.8 before I messed with it Can I leave it as is, and also any voltage adjustment between 0.4 and 0.9 (in case it slides on the enlarged holes over time due to shaking and plastic body deformation due to heat etc.) and still be fine?

 

As long as you still get your 4+ volts at WOT you'll be fine.

 

got it. Thanks much for the info.