Im working on tuning a car that has a cable drive nw 102 tb and with the tb blade all the way closed it still reads in the high .6x range. The problem is i need to crack the tb blade open to get more air in at idle. I have already notched the mounting holes on the tps a little to adjust the voltage down but its still not enough. Im trying to not drill a hole in the blade. has any one else ran into this issue? the car has a fast 102 intake with a 408 and ls3 heads and pretty healthy cam. The car has had this issue with a stock tb also. After talking to the owner the stock tb that was on the car when it was a heads and cam ls1 the tps was notched by another tuner that ran into the same issue. That tuner just drilled a big hole in the tb blade. Im just wondering what would cause this. I have never seen this on any other fbody before. usually you have plenty of adjustment on the throttle cracker.

 

Had one like this also. If you backed it down to .55 voltage, it would bottom the blade out and stick. I ended up leaving it around .60 and drilled a hole in it.

Doubt it's related to the throttlebody at all, but I had to idle this one in open loop to lean it out enough to get it to idle well. Just mentioning it in case you run into something similar.

 

We're thinking it has to be something in the electrical system. I had another (very shady) shop do some work to it a few years ago, and I'm thinking they jumpered something either when they installed the nitrous system, or when I was having problems with the transmission downshifting at WOT (both could have diagnostic issues through the TPS).

I really have NO idea where to start looking for this.

Darril (bigfatls6) says that the TPS creeps up when you turn the key off. He can zero it out, fire it up and it will go back up to 2% or 4% without giving it any throttle. Seems to me like the voltage isn't constant for some reason

He also said that with the key off, he can connect HPTuners to the computer, but it doesn't read anything. Like the computer is always hot, or is storing energy or something

Also, for some reason the transmission (4L80E swap) is always showing to be in first gear, even when it's in reverse

And it's throwing an alternator code as well. Darril could come in and specify which one

I do know that I have something draining the battery with a constant draw, and it's been doing that for a long time. I'm sure whatever is doing that is causing the rest of my misery

Someone please help me with this freakin nightmare so we can get this car right finally. Lol

 

I doubt your issues reside in the TPS voltage, though it is best to be in the .5x range. After building an engine I had an issue with split BLM's at idle and was able to correct it by boring out the IAC passage, turning down the TPS volts to around .55, and keeping IAC counts around 120 when warm. It was a delicate process for sure, there is a write up somewhere out there on how to do this, I'll try to find it.

 

I just realized that I'm not on the LT1 subsection, so this might be different for LS motors.

 

I have put 4 different tps sensors on the car so I know that's not the issue. with the tb all the way closed to where it is just open enough not to stick the tps voltage is still damn near in the .80 range. I slotted the holes on the tps and adjusted the voltage back to about .58 and cracked the throttle body open until voltage was about .65. I can reset the tps back to 0% but as soon as you start the car it will pop back up to 2-3% and stick there until you reset it again. I have even done nothing but turn the ignition off and back on and it would jump from 2-4% and stick there. I have tuned a quite a few cars and have never ran into this issue before.

 

any body know what would cause the high tps voltage? What all effects the tps voltage? The car does have a p1637 code that pops up even though the code is set to 2 no mill light. The code is a generator L-terminal circuit.

 

Here's what I know about troubleshooting a TPS, maybe it'll put you on the right track. The TPS has three wires, the power, signal, and ground. Power should feed it 5v. Signal is what the PCM see's of that 5v while the potentiometer (actuation of the TPS) turns. The ground shouldn't read anything, or very low voltage at most. No more than .01v. Besides checking for the full 5v and voltage fluctuation as the TPS moves, check the ground wire for voltage. If its there, you probably have a bad ground in the PCM.

 

I had the same problem with my SS.

 

there could be a few other sensors sharing the same circuit, as is typical with many systems, however, the multitude of problems points to something else. so, exactly, wht is the timeline for all 4 events? the tps, gen term l, and trans happen after the nitrous instal? after trans swap? all at once, or developed over time, at different times? big stereo installed? good body grounds in and out, and engine ground strap? programing proper, like the trans gear select module adjusted for, if not stock, or actually moving with the actuator shaft? i don't remember 100%, but do believe the l-circuit is the "load sensor" that communicates with he pcm to reference voltage at the pcm vs power cable, or load, etc. i still haven't fully mapped out the features and functions of these delphi alternators. if the circuit has not been modified, and nothing about the nos stands out, that might actually the easier circuit to troubleshoot to point you at the "mogwai".... (source of your gremlin problem)

 

What fixed it??

First, to be clear, the car has been down for 2 1/2 years and has basically had everything changed drivetrain wise. Went from cam/boltons LS1, 4L60E, to now being a 408, 4L80E.

The idle surging and battery killing that it is doing, it was doing the EXACT same thing when we pulled the original motor out.

Going back in time to the original set of mods on the original motor:

Nitrous had been installed for a while when the TPS problem started. It began to occur a little while after the cam swap and the transmission was "stage 3 built" (turned out to only be a shift kit). It surfaced at first when I would be rolling and go WOT and the car would fall flat on it's face for 2-3 seconds and then just pick up and scream all at once. I remember them jacking with the TPS sensor trying to fix it (slotting it as described earlier in the thread)

No big stereo, it has always been stock down to the speakers

Just emailed the tune to HP Tuners and had a segment swap for the 4L80E. Darril hasn't even started trying to tune on the trans yet because he can't until TPS issues get resolved. The shift linkage is all 100% stock...as for the module? I think everything on the 4L80E is as it came..although I do feel we might need to adjust the linkage a little bit (which I understand could be causing some of the problems)

When you say load sensor circuit, are you referring to that single red wire that goes from the alternator to the PCM? We are planning on troubleshooting that, as well as maybe looking into the alternator possibly shorting itself out on the inside.

The only wire I see spliced up by the computer nitrous wise is where they picked up the tach signal, unless it's not getting a good connection (because of the way they spliced it, we plan on looking at that as well)

 

they also spliced into the tps wiring I guess for the throttle activation for the nitrous system. this thing is the craziest thing I have ever seen. i back the throttle cracker back as far as it would go until the blade started sticking and with out slotting the holes on the tps it was still in the high .7x range if I remember correctly. i slotted the tps and backed the voltage down to like .59 as low as I could get it and the tps % woould still change when you would start the car. hell you could do nothing but turn the key to the run position and then back off and on again and the tps would go to like 4% with out the ccar even running. When the car was idling all jacked up and the tps % was at 2% you could back the throttle body craker closed until the tps% would 0 and it would start to idle right but as soon as you turn the key off and on again the tps % would go back up again.

 

Changed out the alternator today, still no improvement....

Edit: The alternator code it was throwing did go away. Everything else is still suckville

 

i had four different shops work on it no one could figure it out. i sold the car and months later i ran into the person who i sold it too. he told me it had to have been a short to ground in the harness. replaced the whole harness and he claimed the car was fine. i find it hard to believe. but that's what he said. maybe try that? Good Luck

 

Last year my car had high idle issues and shift issues that came and went. Ended up being tps. sw, Replaced it and all was good. When I first started it it would idle fine but as you drove it would reset base voltage and idle high. When it was shut off or a little while it would reset and idle fine again. Not sure if its the same issue that U have.

 

I am not surprised at all. Seen that before. Sure hard to convince a guy to do that.

 

You should be able to shoot the wires to see if there is a short to ground instead of replacing a whole harness. All you need is a meter.