TPS reads 2.4% when throttle is closed. WTF?
07-06-2007, 12:51 PM
#41
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Mine has been doing this worse than ever the last few days. But I think I found the solution. Yesterday it was misfiring and doing the high-idle thing, throwing SES and no ASR and I just pulled into the local Chevy dealer, bought a new TPS and installed in the parking lot. The problem disappeared immediately and with over 180 miles later and several run cycles, it hasn't come back. Idles like a different car now.
07-12-2007, 07:42 PM
#43
I had a 99 TA with a similar issue that another shop installed a FAST 90/90 setup on. Initially the blade to crank arm retainer was loose allowing the blade to move more then the crank arm casuing the voltage to vary. That was fixed and now intermittently it will still hang the idle and show 1% throttle.
On this car the voltage at idle can be .60 volts and 0% throttle with the key on not running, but when started and running the TPS will go to .064 volts and show 1% throttle and hang at 1200-1400 RPM. I mention this mainly to show a small voltage change can tell the PCM there is throttle input. If you are seeing a voltahe resolution of only tenths of a volt (.01), you could very well be .08 volts different and show 2-3% throttle. I have seen cars vary back and forth .02 volts and not change the throttle position and it seems a .04 volt change begins the throttle percentage change up from the base setting.
The shop is installing a new Holley 90mm TB to see if this helps as everthing else has been checked similar to what everyone else has done. Of course it is always the tuners fault
Mike Norris
On this car the voltage at idle can be .60 volts and 0% throttle with the key on not running, but when started and running the TPS will go to .064 volts and show 1% throttle and hang at 1200-1400 RPM. I mention this mainly to show a small voltage change can tell the PCM there is throttle input. If you are seeing a voltahe resolution of only tenths of a volt (.01), you could very well be .08 volts different and show 2-3% throttle. I have seen cars vary back and forth .02 volts and not change the throttle position and it seems a .04 volt change begins the throttle percentage change up from the base setting.
The shop is installing a new Holley 90mm TB to see if this helps as everthing else has been checked similar to what everyone else has done. Of course it is always the tuners fault
Mike Norris
07-29-2007, 12:37 AM
#44
We have been chasing this problem for a few years on a few cars. Both 1999 car BTW. What we will see is 0% until you start the car. Once you start the car the voltage drop from starting the car will reset 0% to a lower voltage then it was before the start. Once driving the car it can some times be zero and other times 1-4%.
when we get zero Percent both cars idle perfect. I have asked here and other places a few times but no answers. We will try upping the "TPS throttle position % to disable the main timing tables" to get the idles dialed in but would really like to fix the issue. we have checked grounds and tons of other things. We have had 0% TPS at .56v one moment and 4% at .56v the next.
We have changed TPS sensors, PCMs, grounds, batterys, battery cables, wiring and more things then I can remember over the years.
I hate to see a problem but it is good to see others digging into it!
when we get zero Percent both cars idle perfect. I have asked here and other places a few times but no answers. We will try upping the "TPS throttle position % to disable the main timing tables" to get the idles dialed in but would really like to fix the issue. we have checked grounds and tons of other things. We have had 0% TPS at .56v one moment and 4% at .56v the next.
We have changed TPS sensors, PCMs, grounds, batterys, battery cables, wiring and more things then I can remember over the years.
I hate to see a problem but it is good to see others digging into it!
07-29-2007, 12:39 AM
#45
Yup ALWAYS the tuners fault! 
Good luck with the TB change. We tried that today just to see and no luck
Keep us up to date man!
Good luck with the TB change. We tried that today just to see and no luck
Keep us up to date man!
Originally Posted by Mike Norris
I had a 99 TA with a similar issue that another shop installed a FAST 90/90 setup on. Initially the blade to crank arm retainer was loose allowing the blade to move more then the crank arm casuing the voltage to vary. That was fixed and now intermittently it will still hang the idle and show 1% throttle.
On this car the voltage at idle can be .60 volts and 0% throttle with the key on not running, but when started and running the TPS will go to .064 volts and show 1% throttle and hang at 1200-1400 RPM. I mention this mainly to show a small voltage change can tell the PCM there is throttle input. If you are seeing a voltahe resolution of only tenths of a volt (.01), you could very well be .08 volts different and show 2-3% throttle. I have seen cars vary back and forth .02 volts and not change the throttle position and it seems a .04 volt change begins the throttle percentage change up from the base setting.
The shop is installing a new Holley 90mm TB to see if this helps as everthing else has been checked similar to what everyone else has done. Of course it is always the tuners fault
Mike Norris
On this car the voltage at idle can be .60 volts and 0% throttle with the key on not running, but when started and running the TPS will go to .064 volts and show 1% throttle and hang at 1200-1400 RPM. I mention this mainly to show a small voltage change can tell the PCM there is throttle input. If you are seeing a voltahe resolution of only tenths of a volt (.01), you could very well be .08 volts different and show 2-3% throttle. I have seen cars vary back and forth .02 volts and not change the throttle position and it seems a .04 volt change begins the throttle percentage change up from the base setting.
The shop is installing a new Holley 90mm TB to see if this helps as everthing else has been checked similar to what everyone else has done. Of course it is always the tuners fault
Mike Norris
07-31-2007, 10:02 AM
#47
I seem to have solved the problem. I separated all the wires going from my TPS all the way back to my pcm. I also did this for the wires going to the IAT sensor, MAF and alternator (they're in the same loom). After pulling apart some wires that were stuck together then re-taping, the problem seems to have gone away.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
07-31-2007, 02:19 PM
#48
I Had A Similar Problem But It Turned Out The The Spring In My Tb Just Wasnt Closing 100% When My Car Was Off I Could Reach 0%tps But Every Now And Then Id Be Driving And My Tps Would Read 3-5% With My Foot Off The Gas.. I Called Tsp They Gave Me A Better Spring And Problem Soolved
08-01-2007, 05:49 PM
#49
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Originally Posted by Patrick G
I seem to have solved the problem. I separated all the wires going from my TPS all the way back to my pcm. I also did this for the wires going to the IAT sensor, MAF and alternator (they're in the same loom). After pulling apart some wires that were stuck together then re-taping, the problem seems to have gone away.
08-05-2007, 09:55 PM
#50
I would love to know the fix for this crap. My car started doing this crap last year. I had a MS3 and had it idling good as a **** and was proud of the job I did tuning it. Well one day my car wouldnnt hold idle to save its life once it went into closed loop. I scanned it and noticed that my TPS was 2%. I reset the TPS and it went back to 0%. Started the car and it idled good again. I patted the gas a few times and when the rpm's came back down the TPS was at 2% again. I tried a new TPS and it didnt help.
Now maybe the TPS being at 2% makes it idle high because of changing the spark tables but I tell you something else it does. If you have 2% throttle input the PCM figures the IAC isnt needed and it will go to the 0 position. Now with the IAC closed its gonna be impossible to get a good idle unless you have a big hole in the blade or have the blade opened up a pretty good way with the set screw.
I had ported my TB and there is a little thin washer that goes between bearing and the TPS and I was not sure I put it back. I had originally thought that was the reason my TPS wash anging at 2% but now it looks like it a different problem.
My car is a 99. I thought I read where all of the cars with this problem were 99's?
Now maybe the TPS being at 2% makes it idle high because of changing the spark tables but I tell you something else it does. If you have 2% throttle input the PCM figures the IAC isnt needed and it will go to the 0 position. Now with the IAC closed its gonna be impossible to get a good idle unless you have a big hole in the blade or have the blade opened up a pretty good way with the set screw.
I had ported my TB and there is a little thin washer that goes between bearing and the TPS and I was not sure I put it back. I had originally thought that was the reason my TPS wash anging at 2% but now it looks like it a different problem.
My car is a 99. I thought I read where all of the cars with this problem were 99's?
08-06-2007, 12:36 PM
#51
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Originally Posted by Full-Force
I would love to know the fix for this crap. My car started doing this crap last year. I had a MS3 and had it idling good as a **** and was proud of the job I did tuning it. Well one day my car wouldnnt hold idle to save its life once it went into closed loop. I scanned it and noticed that my TPS was 2%. I reset the TPS and it went back to 0%. Started the car and it idled good again. I patted the gas a few times and when the rpm's came back down the TPS was at 2% again. I tried a new TPS and it didnt help.
Now maybe the TPS being at 2% makes it idle high because of changing the spark tables but I tell you something else it does. If you have 2% throttle input the PCM figures the IAC isnt needed and it will go to the 0 position. Now with the IAC closed its gonna be impossible to get a good idle unless you have a big hole in the blade or have the blade opened up a pretty good way with the set screw.
I had ported my TB and there is a little thin washer that goes between bearing and the TPS and I was not sure I put it back. I had originally thought that was the reason my TPS wash anging at 2% but now it looks like it a different problem.
My car is a 99. I thought I read where all of the cars with this problem were 99's?
Now maybe the TPS being at 2% makes it idle high because of changing the spark tables but I tell you something else it does. If you have 2% throttle input the PCM figures the IAC isnt needed and it will go to the 0 position. Now with the IAC closed its gonna be impossible to get a good idle unless you have a big hole in the blade or have the blade opened up a pretty good way with the set screw.
I had ported my TB and there is a little thin washer that goes between bearing and the TPS and I was not sure I put it back. I had originally thought that was the reason my TPS wash anging at 2% but now it looks like it a different problem.
My car is a 99. I thought I read where all of the cars with this problem were 99's?
But to no avail. 
Still seeing 2% TPS at idle. Back to the drawing board. 
08-08-2007, 09:53 PM
#54
My car is an 02 and it is doing the same thing for the last few months since I had my engine rebuilt. Its driving me nuts! I have replaced the IAC, f-ed around for hours with the TB set screw, and reset the TPS with no change. I have a new TPS on the way and I hope that resolves it. When I put that in I will also try pulling all the wires apart as someone else said. If anyone can figure this out I will take you out and buy all your beers all night long. And if you dont live near me I will put a case of the beer of your choice in the mail. NO JOKE! 
08-08-2007, 10:49 PM
#55
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I hate this F%^^$$^&^ computer.
After reading this thread I wonder two things.
1. How is throttle % calculated? map,maf,tps...or just tps or map and tps? I m betting map and tps, cause you can get a ses for a non relation between the two.
2. It seems like many of those in the thread have had the intake off, or are older cars, which raises the possibility of a vacuum leak. Maybe the map oring, brake booster line etc...anything, that may even be related to bumps in the road. This would cause a % rise in th even though the th blade is fully closed if the th % is calculated using more info then just the tps.
After reading this thread I wonder two things.
1. How is throttle % calculated? map,maf,tps...or just tps or map and tps? I m betting map and tps, cause you can get a ses for a non relation between the two.
2. It seems like many of those in the thread have had the intake off, or are older cars, which raises the possibility of a vacuum leak. Maybe the map oring, brake booster line etc...anything, that may even be related to bumps in the road. This would cause a % rise in th even though the th blade is fully closed if the th % is calculated using more info then just the tps.
08-09-2007, 12:16 PM
#57
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Originally Posted by Patrick G
I'm checking all connections this weekend. I'm convinced it's some kind of electrical gremlin and most likely a loose or corroded connection somewhere. If I fix it, I'll definitely post back.
08-09-2007, 01:07 PM
#58
Originally Posted by 1320
I hate this F%^^$$^&^ computer.
1. How is throttle % calculated? map,maf,tps...or just tps or map and tps? I m betting map and tps, cause you can get a ses for a non relation between the two.
1. How is throttle % calculated? map,maf,tps...or just tps or map and tps? I m betting map and tps, cause you can get a ses for a non relation between the two.
and last i checked the regular cable driven throttle doesn't do any calculations, it's just a map of voltage to TPS%. electronic throttle cars are a different story of course.I dont have the manual on me right now but it think the code will be thrown if your TPS voltage at idle is above 0.65volts. you can monitor your TPS voltage from HPT/EFI scanner. it's best to do it with two people, one sits in the car with the laptop yelling out voltage readings, the other person tweaks the idle screw so you know when you hit the maximum adjustment without going over the 'legal' voltage so it doesn't throw codes. once you find a happy setting, don't forget to reset the TPS so the computer learns where the new '0%' is; i know it's a silly thing to mention but i can think of dozen cases where that was the only piece of the puzzle missing.
if you get a SES with less than 0.65v TPS voltage (again please check manuals for the precise value, i haven't played with that in person in a while) then it's a different issue. TPS sensors sometimes just die very slowly causing all kinds of strange symptoms that don't look like they're TPS related, just ask any 04-05 Yamaha R1 owners (http://www.sportbikes.net/forums/showthread.php?t=7320)
08-09-2007, 03:12 PM
#59
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I have monitored the voltage and the throttle %. With the same voltage I have seen the the % can change. Does anyone no how the PCM calulates this. I will bet the is more that a table. I would love to find out.
RedHardSupra how do you reset the TPS? I have done the unpulg and turn on and turn off thing alot with no results.
Thanks for the help
RedHardSupra how do you reset the TPS? I have done the unpulg and turn on and turn off thing alot with no results.
Thanks for the help
08-09-2007, 07:01 PM
#60
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I just got finished working on a 98' having the same problem. Decided to check the fit of the TPS on the throttle shaft. Found that it was loose and had absolutely no press fit. What I done was wrapped some clear tape around the shaft til the sensor went on tight. Then reset the TPS by unpugging it and turning key on. Problem has completey gone away and the car runs great now.
I am not saying this is the fix for everyone, it just happened to be the cause of this cars issues. Hope this helps.
Nick
I am not saying this is the fix for everyone, it just happened to be the cause of this cars issues. Hope this helps.
Nick