bmcr

I read to loosen the torx screws and adjust the sensor by rotating it. Maybe I'm just dense but can some one give me a more detailed explanation?
Are we loosening the two torx screws that hold the sensor into place?
How do you rotate the sensor?

Nathan Plemons

The TPS is attached to the throttle body by way of two torx screws. Loosen these slightly and the sensor should rotate around it's center axis allowing you to set it's base voltage reading. This works great for TPI cars, 85-91.

If, however, your car is an LT1/LT4, 92-96 the TPS is still held on with 2 torx screws but the sensor is not slotted so there is no adjustment because there is none needed.

What year is your car?

Joe C

that would help, the year that is...

on my 85, the TPS mounting point or points were slotted, allowing for rotation and adjustment, but my 90 wasn't. i'm guessing the factory re-designed it so the WOT and idle stop were at pre-determined values. not sure when they went from adjustable to non-adjustable TPS on the L98 engines.

65Z01

I believe '85-'89 L98s had slotted (adjustable) TPS, but '90-'91 did not.

Though factory procedure is adjust for .52Vdc at base idle I prefer to set .65Vdc at base idle or ~.75Vdc at normal idle of 600-700rpm.

For the top end just adjust for max value, as close to 5Vdc as possible.

I like to losten the top screw till loose and the just crack the bottom screw, so that it takes a little force to rotate the TPS unit.

Set the idle value first and then the max value; then go back to verify idle value has not changed.

Paul Workman

The LT5s use a modified L98 ECM and also have the slotted TPS as well. (The recommended voltage is ≈0.54. If I'm not mistaken, you can see the TPS (black thing) and it's torks screws mounting it to the TB at the upper left end of my avitar picture...How conveeeeenient!) Anywayz, I was just curious why you recommend the higher voltage setting for base operation?

My reason for asking is my idle is set to 750 rpm to boost the idle air speed a bit on a fully ported LT5, yet the recommendation remains the 0.54vdc value. I am experiencing a minor annoyance under decelleration at zero throttle angle - the idle "hunts" with the clutch engaged and occationally stalls.

A couple LT5 tuner friends of mine - one actually did the tuning - believe the fix amounts to a tweak to the low speed AF table, and they may well be right. But, your recommendation for a slightly higher setting comiserate with the higher idle rpm seems logical. So, I'm guessing the higher voltage at idle may be more the result of something else, e.g., setting the WOT voltage, and not by design, specifically, yes?

Thanks in advance,

P.

bmcr

Sorry guys, The car is a 1991

SunCr

'91 isn't adjustable. Old tech was, but not for any specific reason other than as resistance increases in old wiring, sensing voltage drops. The range simply allowed for that wear and the established spec was at the mid point of the range. New tech handles the wear by accepting startup voltage as idle voltage. TPS wear is minimal until about 200,000, maybe 300,000 miles and easy to diagnose with a analog voltimeter. Digital and anything on a scanner will average values and not give you the whole story.