Throttle Position Issues... Kinda Urgent

Philbar71 · 03-08-2012, 10:23 AM

So on the way to work this morning Im driving through stop and go traffic and i notice all the suddenly the throttle is sticking. It starts to idle around 1000 RPMs (vs 600) in gear, in neutral it idles at about 1200 RPM. So I get to work and check the TB and the throttle is fully closing and opening properly.

I go back out on my break and read the TPS with my code reader and notice that when the car is off it reads 0.8% and when I start the car it jumps up to ~1.8% The throttle feels like its fully closed, thats the thing. Before I leave for home I will take off the intake and make sure nothing is obstructing the throttle plate or anything dumb like that.

But is this possibly a sign of a failing TPS? its fairly old, one from a mid 90s Quad TB too.

Anybody have any suggestions?

[ion] C2 · 03-08-2012, 10:39 AM

Yep TPS.

Or IACV issues.

Philbar71 · 03-08-2012, 10:46 AM

I had kinda figured, but the TPS does not actually open or close the valve right? How would that make it idle faster? Unless it is also the IACV dying at the same time. But, when I started up on my break, it idles high normally like it does when its cold and gradually slows down the idle speed to about 1200 and just sits there.

[ion] C2 · 03-08-2012, 10:51 AM

TPS just monitors throttle plate position. Based on this measured throttle position, other things happen. Since your TPS voltages are changing when the throttle is not applied, there is a definite issue witih the TPS.

IACV opens and closes a small hole to allow air in. Based on the TPS, it could change how far open it becomes. If the TPS is saying it's at 1-2% throttle, the IACV would open a bit too, causing your perceived vacuum leak.

This could also be a vacuum leak elsewhere, but in my significant experience with vacuum leaks, your problem seems to be solely with the electronics at the throttle body.

Shiwnath · 03-08-2012, 11:14 AM

I just changed the TPS in my Dad's sunfire yesterday for a low voltage code. Luckily for him when I bought my 65mm TB, the seller was awesome enough to include the IAC and TPS. The TPS was identical thanks to GM using the same sensor in many of its models around the same years. Doesn't the mid 90s TB us a slightly different TPS?

Philbar71 · 03-08-2012, 11:14 AM

Quote:

Originally Posted by [ion] C2

TPS just monitors throttle plate position. Based on this measured throttle position, other things happen. Since your TPS voltages are changing when the throttle is not applied, there is a definite issue witih the TPS.

IACV opens and closes a small hole to allow air in. Based on the TPS, it could change how far open it becomes. If the TPS is saying it's at 1-2% throttle, the IACV would open a bit too, causing your perceived vacuum leak.

This could also be a vacuum leak elsewhere, but in my significant experience with vacuum leaks, your problem seems to be solely with the electronics at the throttle body.

Ahhhh yes... That makes perfect sense. Thanks for the wisdom!

Quote:

Originally Posted by Shiwnath

I just changed the TPS in my Dad's sunfire yesterday for a low voltage code. Luckily for him when I bought my 65mm TB, the seller was awesome enough to include the IAC and TPS. The TPS was identical thanks to GM using the same sensor in many of its models around the same years. Doesn't the mid 90s TB us a slightly different TPS?

Yeah its slightly different than what the LD9 uses, similar in design just slight differences.