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Adjusted TPS to 0.54, now idles at 1300

Old 06-01-2018, 08:21 PM
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Originally Posted by TheBlaster9001 View Post
Third time (or TPS) lucky, I hope.
Nope... Picked up my new Delco p/n 213-905, checked it first by running the 10g jump wires from 5v reference and ground, then measured middle pin output. WOT: 3.2v. Literally not kidding.

It seems like on all of these bad sensors, the first 20-25% of lever travel produces no voltage. I still installed it to try something. Installed and angled all the way up, with the set screw completely screwed in, the most it'll read at "idle"' was .30. At this point all I can do is laugh. I don't believe there is a way I can adjust the actual lever. Maybe I need to hit the junk yards tomorrow and find an authentic period correct 3 wire GM TPS
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Old 06-01-2018, 08:28 PM
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Originally Posted by JasBass View Post
Nope... Picked up my new Delco p/n 213-905, checked it first by running the 10g jump wires from 5v reference and ground, then measured middle pin output. WOT: 3.2v. Literally not kidding.

It seems like on all of these bad sensors, the first 20-25% of lever travel produces no voltage. I still installed it to try something. Installed and angled all the way up, with the set screw completely screwed in, the most it'll read at "idle"' was .30. At this point all I can do is laugh. I don't believe there is a way I can adjust the actual lever. Maybe I need to hit the junk yards tomorrow and find an authentic period correct 3 wire GM TPS
Bad batch certainly isn't out of the question. Back in the early 2000's aftermarket clutch slave cylinders were manufactured with the plunger installed backwards!

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Old 06-01-2018, 08:41 PM
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Originally Posted by GREGGPENN View Post
Bad batch certainly isn't out of the question. Back in the early 2000's aftermarket clutch slave cylinders were manufactured with the plunger installed backwards!

This whole thing just blows my mind. Two bad BWD TPS and a bad Delco. I'm not even sure I want to order a new unit anymore, it seems the manu. tolerances are garbage. Third gen Camaros tend to plentiful around here, especially in the JY
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Old 06-01-2018, 08:41 PM
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Originally Posted by JasBass View Post
Nope... Picked up my new Delco p/n 213-905, checked it first by running the 10g jump wires from 5v reference and ground, then measured middle pin output. WOT: 3.2v. Literally not kidding.

It seems like on all of these bad sensors, the first 20-25% of lever travel produces no voltage. I still installed it to try something. Installed and angled all the way up, with the set screw completely screwed in, the most it'll read at "idle"' was .30. At this point all I can do is laugh. I don't believe there is a way I can adjust the actual lever. Maybe I need to hit the junk yards tomorrow and find an authentic period correct 3 wire GM TPS
Jesus. We did confirm that the signal wire had low resistance right? At this point it may be worth finding a 5v power supply and bench testing the TPS sensor. That way we can know if it's the wiring or not. Alternatively, you could jumper +5v and ground from any other 5 volt sensor's connector (MAP or MAF, for example) and measure the signal voltage.

i.e., a test lead from MAP or MAF 5v pin to the tps bottom socket, a test lead from MAP or MAF ground to pin top socket, then measure voltage between the signal and ground wire.

I'm not 100% convinced the sensor is bad, doing a bench test or using differnt wiring would help shift the blame off the TPS. The no tps voltage uptake until 25% just reminds me exactly of what happened when I wired my MAP sensor backward. Because my MAP and TPS shared a ground, the backwards wiring (5v to ground, ground to 5v) on the MAP threw the TPS off.
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Old 06-01-2018, 09:01 PM
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Originally Posted by TheBlaster9001 View Post
Jesus. We did confirm that the signal wire had low resistance right? At this point it may be worth finding a 5v power supply and bench testing the TPS sensor. That way we can know if it's the wiring or not. Alternatively, you could jumper +5v and ground from any other 5 volt sensor's connector (MAP or MAF, for example) and measure the signal voltage.

i.e., a test lead from MAP or MAF 5v pin to the tps bottom socket, a test lead from MAP or MAF ground to pin top socket, then measure voltage between the signal and ground wire.

I'm not 100% convinced the sensor is bad, doing a bench test or using differnt wiring would help shift the blame off the TPS. The no tps voltage uptake until 25% just reminds me exactly of what happened when I wired my MAP sensor backward. Because my MAP and TPS shared a ground, the backwards wiring (5v to ground, ground to 5v) on the MAP threw the TPS off.
I think a good bench test is def in the works. I was incredibly careful to make sure I ran wires appropriately for this test. I made sure it was getting 5v from reference and confirmed it stayed 5v throughout the range. The MAF is a new Bosch unit and the connector only fits in one way. Chances of that being messed up?? And yessir, confirmed I had 0 ohm resistance on the signal wire (we went through the de-pinning process). I started to think it was the car, but then I realized that the BWDs read different outputs, one below 2, the other just over 2, and now the Delco reads 3.2. If the car was at fault, I would imagine it would be failing at similar voltage outputs?
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Old 06-01-2018, 09:28 PM
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Originally Posted by JasBass View Post
I think a good bench test is def in the works. I was incredibly careful to make sure I ran wires appropriately for this test. I made sure it was getting 5v from reference and confirmed it stayed 5v throughout the range. The MAF is a new Bosch unit and the connector only fits in one way. Chances of that being messed up?? And yessir, confirmed I had 0 ohm resistance on the signal wire (we went through the de-pinning process). I started to think it was the car, but then I realized that the BWDs read different outputs, one below 2, the other just over 2, and now the Delco reads 3.2. If the car was at fault, I would imagine it would be failing at similar voltage outputs?
Unlikely that the MAF itself is causing it, but you could try to see how high the TPS will get with the IAC and MAF, and IAT off. If I remeber correct all those share a ground, it could be telling to test with these all off, then just one off at a time. The IAT is on the underside of the intake.

If the issue was like mine, I would suspect consistent outputs from the TPS sensors. But if there was a bad ground, the signal voltage could be different.
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Old 06-02-2018, 02:00 AM
  #67  
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Originally Posted by JasBass View Post
I think a good bench test is def in the works. I was incredibly careful to make sure I ran wires appropriately for this test. I made sure it was getting 5v from reference and confirmed it stayed 5v throughout the range. The MAF is a new Bosch unit and the connector only fits in one way. Chances of that being messed up?? And yessir, confirmed I had 0 ohm resistance on the signal wire (we went through the de-pinning process). I started to think it was the car, but then I realized that the BWDs read different outputs, one below 2, the other just over 2, and now the Delco reads 3.2. If the car was at fault, I would imagine it would be failing at similar voltage outputs?
I thought you did the bench test already with cranking the TPS arm all the way or did I read you wrong?
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Old 06-02-2018, 08:32 AM
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Originally Posted by aklim View Post
I thought you did the bench test already with cranking the TPS arm all the way or did I read you wrong?
I was thinking an off-car bench test - that would tell us if the sensor is acting up with the most certainty.
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Old 06-02-2018, 09:35 AM
  #69  
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How about checking resistance of the units off the car?
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Old 06-02-2018, 10:25 AM
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Originally Posted by aklim View Post
I thought you did the bench test already with cranking the TPS arm all the way or did I read you wrong?
You're right, I did. I phrased that bad in the post. I was coming off a 30 hour shift... TPS off the car and arm cranked all the way down got me like 3.4.

Originally Posted by TheBlaster9001 View Post
I was thinking an off-car bench test - that would tell us if the sensor is acting up with the most certainty.
So here is what I just did. Sensor off the car, I did use the 5v feed from the connector, but then I grounded out the top pin to chassis to remove any other sensor interference. Confirmed it was receiving and grounding 5v. Measured voltage from the middle pin and received exactly the same as I did from the initial test. To even get to 0.54v, the arm was like halfway through the rotation. Only thing that all this comes back to is bad manu. tolerances of these "new old" parts. Going to hit the JY later this morning and see if I can find an original TPS

Originally Posted by JimLentz View Post
How about checking resistance of the units off the car?
About to do that as well. With such a nice day today, I was looking forward to getting some miles in
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Old 06-02-2018, 11:49 AM
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Originally Posted by JasBass View Post
You're right, I did. I phrased that bad in the post. I was coming off a 30 hour shift... TPS off the car and arm cranked all the way down got me like 3.4.



So here is what I just did. Sensor off the car, I did use the 5v feed from the connector, but then I grounded out the top pin to chassis to remove any other sensor interference. Confirmed it was receiving and grounding 5v. Measured voltage from the middle pin and received exactly the same as I did from the initial test. To even get to 0.54v, the arm was like halfway through the rotation. Only thing that all this comes back to is bad manu. tolerances of these "new old" parts. Going to hit the JY later this morning and see if I can find an original TPS



About to do that as well. With such a nice day today, I was looking forward to getting some miles in
Sounds like another bad sensor then. What a headache.
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Old 06-02-2018, 02:26 PM
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Originally Posted by TheBlaster9001 View Post
Sounds like another bad sensor then. What a headache.
Junk yards were fruitless. Stopped by a friend's shop that used to be a gm dealership back in the late 80s and early 90s, the parts room is untouched since it shut down. No TPS in the old stock. But found some sweet stuff in there. Old SBC heads never installed still in their factory wrap.
Stopped off at advance and talked to them about the issues. We talked over some options and they found an alternate part number for a BWD TPS using 3rd gen L98 Camaro info. It was like twice the price of the other one, ACDelco territory. I'll have it in the morning and we'll roll the dice on this one. Worst worst case, i'll stop off at the dealership and see what they think
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Old 06-03-2018, 01:18 PM
  #73  
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New alternate pn for the TPS and got 3.4 at WOT. I ohm'd both of the TPSs (BWD and Delco) and got the below results. They seem in line from the ones referenced earlier in this thread. I just want to bang my head. How can this be this difficult, 4 TPS reading low voltage when receiving 5v reference...

BWD
A-C: 6.79
A-B: 3.3
C-B: 9.8

Rotating sweep
A-B: 3-8
C-B: 9.8-2

Delco
A-C: 6.74
A-B: 3.4
C-B: 9.8

Rotating Sweep
A-B: 3.4-8.3
C-B: 9.8-1.5
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Old 06-03-2018, 03:24 PM
  #74  
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n Autozone Duralast should work fine. Mine has been fine for over a year.
I do notice they start in the more rotated position to get .54, but you have to move the tps sensor around a little more than stock.
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Old 06-03-2018, 03:59 PM
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Originally Posted by xrav22 View Post
n Autozone Duralast should work fine. Mine has been fine for over a year.
I do notice they start in the more rotated position to get .54, but you have to move the tps sensor around a little more than stock.
Getting to 0.54 isnít really the issue, itís the fact that none of the 4 brand new sensors Iíve bought will read over 3.5v at WOT. They all read low at WOT. Iím curious now if I can notch the cut off nub that stops it at ďWOTĒ so the lever can continue to progress and get higher voltage
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Old 06-03-2018, 04:23 PM
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I am pretty sure WOT is anything 3.5 and over. Start it over .54 and get an error. Here is a read on the subject.
https://www.corvetteforum.com/forums...ain-still.html
I have never checked mine other than it went up and down smooth.

Last edited by xrav22; 06-03-2018 at 04:25 PM.
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Old 06-03-2018, 05:13 PM
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Originally Posted by xrav22 View Post
I am pretty sure WOT is anything 3.5 and over. Start it over .54 and get an error. Here is a read on the subject.
https://www.corvetteforum.com/forums...ain-still.html
I have never checked mine other than it went up and down smooth.
That was a decent read. I just sorta ran a little backyard mechanic experiment and failed . Took the original TPS that was overly messed up and notched the cutoff and tried to see if it would read more volts if the lever went more. It read like .2 more before it must have reached a cutoff and lost contact internally; it dropped to 0. I emailed ACDelco for an opinion to see what they have to say. I posted out to the parts section to see if anyone is selling a TPS that had been bench tested good. It still concerns me that the TPS at max lever only reads 3.4
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Old 06-12-2018, 10:40 PM
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Ok...Update. Bought an original working TPS from another forum member from an 88. It actually works! Got it installed and went through the entire idle reset process, followed every word. Took it out for a spin and everything seemed like it was on track, idled between 7-8, great throttle response, car just felt more alive. Stopped for gas, obviously turned the car off, filled up, then restarted the car and it immediately idled at 1500
It absolutely would not kick down to anything less than 1500. Came home and popped the hood and I heard a little hiss that I hadn't heard before. Seems like I have a vac leak at the brake booster vac line elbow. Pushed in on the fitting and the hiss stopped, but the high idle did not. I'm confident the idle set screw and TPS are where they need to be. It worked well before tuning off. With IAC pintle fulled extended (A+B jumped, disconnected, etc.), it'll idle between 4-5. I know vac leaks can lead to a high idle, but I don't think 1500 would happen from a vac leak like that would it?
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Old 06-12-2018, 11:06 PM
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Originally Posted by JasBass View Post
Ok...Update. Bought an original working TPS from another forum member from an 88. It actually works! Got it installed and went through the entire idle reset process, followed every word. Took it out for a spin and everything seemed like it was on track, idled between 7-8, great throttle response, car just felt more alive. Stopped for gas, obviously turned the car off, filled up, then restarted the car and it immediately idled at 1500
It absolutely would not kick down to anything less than 1500. Came home and popped the hood and I heard a little hiss that I hadn't heard before. Seems like I have a vac leak at the brake booster vac line elbow. Pushed in on the fitting and the hiss stopped, but the high idle did not. I'm confident the idle set screw and TPS are where they need to be. It worked well before tuning off. With IAC pintle fulled extended (A+B jumped, disconnected, etc.), it'll idle between 4-5. I know vac leaks can lead to a high idle, but I don't think 1500 would happen from a vac leak like that would it?
Good lord, it really was a bunch of bad sensors. What a mess!

I was working on the girlfriends 86 this weekend, chasing a high idle. The idle reset process worked for it, but it would jump up when the engine light for IAT sensor came on when idling for ~30 secs after warming up.

So for whats it's worth, check for any trouble codes. A big enough vac leak may have set a code.

A bolt recently shook it's way out of my plenum, which led to an idle that was either 500, or 1200, it would jump up and down. That was a big leak, but is an example of how goofy the computer can respond to a leak.
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Old 06-12-2018, 11:27 PM
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Originally Posted by TheBlaster9001 View Post
Good lord, it really was a bunch of bad sensors. What a mess!

I was working on the girlfriends 86 this weekend, chasing a high idle. The idle reset process worked for it, but it would jump up when the engine light for IAT sensor came on when idling for ~30 secs after warming up.

So for whats it's worth, check for any trouble codes. A big enough vac leak may have set a code.

A bolt recently shook it's way out of my plenum, which led to an idle that was either 500, or 1200, it would jump up and down. That was a big leak, but is an example of how goofy the computer can respond to a leak.
Checked for codes and throwing none. As much as I love these cars, these older computer systems really can be a pain when something isn't right. I'll hit the elbow with some RTV in the morning and try again after work. I swear, I feel like I can hear the IAC motor on when turning the car off. Re start and it idles high. I will not be defeated by a car!
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