92 LT1 - TPS voltage/idle issues
03-19-2019, 01:20 PM
#1
92 LT1 - TPS voltage/idle issues
Hey, I have been chasing an issue. I had higher then normal idle, generally around 1100, on occasion at a light i could get it to drop down to 900ish. I was thinking the car was staying in open loop mode and just never going into closed loop. I replaced the IAC, cleaned out the passage etc, same thing. I got Datacat setup and saw the TPS voltage was higher .74-,84ish. I realized that someone had messed with the throttle plate screw and it was just holding it open to far. Easy fix, turned it down and the idle dropped down in the 800 range.
This is a 383 built motor with an aftermarket ECM program, so higher idle is what I expect. But my TPS voltage was only going down to .72ish, it does not have any adjustment on it, and sometimes the TB was sticking slightly open (0.4% ). So I took the TB off and cleaned it up really good. Now its showing closing to 0%, but idling down low enough it dies (when cold), TPS voltage is still .72v ish, AND when warm it wants to idle at 1500-1800, stab the throttle at a light, and it will pop down to 800rpm....
So NOW I am wondering if its ever going into open loop for warm up, and all this playing around has tricked the system into setting the 0 throttle in the wrong place.
With built lumpy idle motor, should I even be trying to get the TPS voltage to 0.54?
Also I found charcoal in the Evap line, so have a new Evap solenoid coming, and will clear out the line, replace the canister.
Sorry for the scattered thoughts, just trying to see if anything triggers people to say "Oh go look for XYZ".
Thanks
This is a 383 built motor with an aftermarket ECM program, so higher idle is what I expect. But my TPS voltage was only going down to .72ish, it does not have any adjustment on it, and sometimes the TB was sticking slightly open (0.4% ). So I took the TB off and cleaned it up really good. Now its showing closing to 0%, but idling down low enough it dies (when cold), TPS voltage is still .72v ish, AND when warm it wants to idle at 1500-1800, stab the throttle at a light, and it will pop down to 800rpm....
So NOW I am wondering if its ever going into open loop for warm up, and all this playing around has tricked the system into setting the 0 throttle in the wrong place.
With built lumpy idle motor, should I even be trying to get the TPS voltage to 0.54?
Also I found charcoal in the Evap line, so have a new Evap solenoid coming, and will clear out the line, replace the canister.
Sorry for the scattered thoughts, just trying to see if anything triggers people to say "Oh go look for XYZ".
Thanks
03-19-2019, 04:18 PM
#2
Adding more information.
After posting this I was thinking about it. I have an Edelbrock BBK 58mm throttle body. I realized that it being completely closed maybe just not at 0.54volts on the TPS, and thats ok. So maybe my stressing about that isnt an issue. The computer sees the .74ish volts as 0% throttle (according to datacat), so maybe thats already programed into the computer as its 0 point. And me trying to force it below that is just forcing the throttle butterflys to bind up some....
Does that sound feasible?
After posting this I was thinking about it. I have an Edelbrock BBK 58mm throttle body. I realized that it being completely closed maybe just not at 0.54volts on the TPS, and thats ok. So maybe my stressing about that isnt an issue. The computer sees the .74ish volts as 0% throttle (according to datacat), so maybe thats already programed into the computer as its 0 point. And me trying to force it below that is just forcing the throttle butterflys to bind up some....
Does that sound feasible?