thanks for posting up for the searches to find! glad you got it

 

And thank you for the positive feedback. Its satisfying to know that I was able to help. Very few people take the time to post the final resolution of the problem, or to thank anyone.

 

How many grounds are there on the car?

 

I'm bringing this back from the dead, chasing a similar problem myself, right now.

 

I had this problem for a while. I got autotap and adjusted my throttle blades on the car to compensate for my IAC position. Then I adjusted the TPS to compensate. One reason for my problem is that I had replaced my throttle body and I just went ahead and bought another tps from autozone and slotted it etc to adjust for the new throttle body(this tps was not OEM). Eventually I got the old stock one back out and slotted it and put it on and I have not had the problem since. So if you have to replace the tps make sure you do it with and OEM GM part..

 

I have a slotted OEM GM (NEW) TPS on the car now. I also have a Holley 52mm TB. How did you adjust your throttle blades through auto-tap. I'm using the Aeroforce interceptor gauge to read my TPS voltage on the top and the bottom. I checked it before adjusting, closed it read .39v and WOT it read 4.54v. I adjusted the closed setting to .58v and my WOT went up to 4.74v ( I believe this is to high ). I started throwing codes almost immediately as soon as I would go WOT with the car. I'm wondering if the HOLLEY TB has a slight bit of play on the center shaft, I could actually get the closed TPS voltage to change slightly from .39v to .23 by grabbing the throttle blade cam and closing it a touch more ( almost like a nudge ). It's got me thinking that the TPS voltage is moving about .20v at closed or open. So, when I set the closed correct, it's adding .20v (roughly) to the 4.54v it should have as WOT (4.54v + .20v (center shaft play) = 4.74v) which I believe is way over and will throw the TPS code for high voltage. I might have to send the TB to Holley and see what they can do about the problem. Any suggestions or does my logic seem sound. I was under the impression the closed voltage should be in the range of .55v to .60v and the WOT 4.47 to 4.55 ?

Thoughts please.....

Maybe Engineer can shed some light on this problem ?

 

I am pretty sure that anything under 4.9V is fine.. What codes are you getting?

 

I had the same problem with the Holley 58mm TB.... the problem was the stamped metal throttle "stop" lever was sitting in a slot milled in the thick aluminum throttle body accel cable quadrant. The lever would move slightly in the slot. I had to pin the metal stop to the aluminum quadrant.

What code do you get when you have the 4.74V WOT setting? You shouldn't be getting a code, unless its got a voltage "spike" somewhere in the throttle sensor when you rotate it. You mention that your TPS is already slotted. Are you sure its the correct one? The LT1 TPS is not slotted.

 

Injuneer,
It sounds like you have had a similar problem to what I'm experiencing with my 52mm Holley. I can actually grab the throttle cam (drivers side) at the (supposed) closed position and get it to move just a tiny bit which translates into that .20v change. I'm wondering if the .20v change is jumping by that amount on the WOT run. 4.74v when I check it, then when I go WOT if it moves that .20v (roughly) it would be 4.74v + .20v (give or take a little) = 4.94v minimum (maybe a spike like you suggested). I'm wondering if this is the problem ? As the throttle stop closes after the WOT run I'm wondering if I don't get the .20v reduction back on the bottom end. My closed voltage is now set at roughly .56v to .58v.

My TPS sensor was not slotted as new, I had to slot the unit to adjust the TPS into range on this throttle body. If I had just left the (new) OEM LT1 TPS sensor and put it into the Holley TB my closed TPS voltage was something like .19v and it would throw codes like crazy for low voltage. Not to mention the throttle was very lazy at that closed TPS voltage.

Codes: (When I adjusted the TPS voltage to .58v (closed), 4.74v (WOT)
0123
1121
1664 (I believe this to be un-related to my problem)

Codes: (original position TPS voltage .39v (closed), 4.54v (WOT)
I can't remember the two codes but they were something to the effect of low TPS voltage and I still got the 1664 (I think this is un-related to my problem).

 

P1664 indicates your skip-shift solenoid is disconnected. Why not put a 2000 ohm resistor in the harness connector for the solenoid, to eliminate that code?

Everything points to the erratic TPS voltage. My Holley problem was a major issue, because I run an aftermarket ECU that requires that I input the closed throttle and WOT TPS voltages, so the ECU can interpolate the throttle percent position. So +/- a few tenths of volt could cause problems. But the stock PCM is supposed to be able to accept TPS voltages in the range of 0.20-0.90V and set that as the baseline for the TP % calculations.

Have you watched the TPS voltage as you s-l-o-w-l-y rotate the throttle blades through their full range of motion, looking for that spike that is causing the problem? Recognize though that the voltage would have to exceed 4.90V for at least on second to set the code. An intermittent short between the gray 5V reference supply wire and the dark blue signal wire would be a more likely cause.

 

Injuneer,

I reset the TPS sensor position so it reads .45v closed & 4.74/76v @ WOT. Cleared my codes and now the car seems to run perfectly fine, I'm still getting a p1664 code, could my skip shift eliminator (about 5 years old) be failing after all this time ?

 

Good possibility there is a problem with the wiring to the skip shift eliminator, or the eliminator itself. Its only a 10-cent resistor in a plastic housing.

 

I suppose after 5 or 6 years of service I should just replace the $10 item. Thanks for the help Injuneer....