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TPS, might be going bad by 88Ironduke
Started on: 08-04-2003 09:57 PM
Replies: 8
Last post by: stuartlowery on 08-07-2003 02:40 AM
88Ironduke
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Report this Post08-04-2003 09:57 PM Click Here to See the Profile for 88IrondukeClick Here to Email 88IrondukeSend a Private Message to 88IrondukeDirect Link to This Post
While checking out my stumbling problem on my V6, I decided to start checking out sensors and stuff.

I've got a new cap/rotor, plugs/wires, ignition module and coil. I haven't changed the pick up yet.

So, things I have found.
The ECM is throwing no codes,

IAC very difficult to move in and out. Cleaned the ports with EFI cleaner, got the IAC moving a bit better after fooling with for a couple of min. I just read a post by the ogre on testing the IAC, will do that tomorrow.

checked the resistence on the TPS. Ohms were nice and steady on the meter untill about part throttle, it went O.L. on my fluke but started giving a reading again at about 3/4 throttle. I assume this means a bad TPS. Its not throwing a code though, how can this be. If I accelerate slowly & smoothly, its fine. If I nail the gas, it stumbles and then accelerates.
Its not throwing a code, so I am a little puzzled. Anyone else found this on a TPS?
Thanks
88Ironduke

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SpideR W
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Report this Post08-05-2003 12:16 AM Click Here to See the Profile for SpideR WSend a Private Message to SpideR WDirect Link to This Post
Sure sounds to me like a bad TPS. Anytime a POT does that, it isn't right. What is possible that the heat, airflow, and vibration found in the engine compartment allow it to make intermittant contact through the bad range, and so the ecu doesn't lose it long enough to throw a code? Dunno if that would cause the stumbling either, but from the readings you got, I would replace it.
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stuartlowery
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Report this Post08-05-2003 01:39 AM Click Here to See the Profile for stuartloweryClick Here to visit stuartlowery's HomePageClick Here to Email stuartlowerySend a Private Message to stuartloweryDirect Link to This Post
I'm not sure what FLUKE you have bt I've had a digital meter do the same. Thsi was due to the meter switching ranges. Then I used an analog and noticed the TPS was fine. Back up your findings with an analog meter and watch the needle.
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jelly2m8
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Report this Post08-05-2003 01:52 AM Click Here to See the Profile for jelly2m8Click Here to Email jelly2m8Send a Private Message to jelly2m8Direct Link to This Post
 
quote
Originally posted by stuartlowery:

I'm not sure what FLUKE you have bt I've had a digital meter do the same. Thsi was due to the meter switching ranges. Then I used an analog and noticed the TPS was fine. Back up your findings with an analog meter and watch the needle.

Yep, always use a good old analog meter for checking these things.

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GTDude
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Report this Post08-05-2003 04:42 AM Click Here to See the Profile for GTDudeClick Here to Email GTDudeDirect Link to This Post
GM recommends using ONLY a DVOM to check any wiring going to an ecm system. You DEFINITELY have a bad TPS if it skipped like you said. Good luck.

Phil

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86 FIERO SE 2.5 AUTO
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If you found my advice helpful, please take the time to give me a positive rating. Thanks

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88Ironduke
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Report this Post08-05-2003 06:01 AM Click Here to See the Profile for 88IrondukeClick Here to Email 88IrondukeDirect Link to This Post
Thanks
I don't have an analog meter, so I have to wing it. I'm going to put in new TPS and see how it runs. I hate trouble guessing, but I don't have any codes and I know this thing can run better than it is.

88Ironduke

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DRH
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Report this Post08-05-2003 08:23 AM Click Here to See the Profile for DRHClick Here to Email DRHSend a Private Message to DRHDirect Link to This Post
The ECM won't set a code unless it's less than .2 volts for 2 seconds or more than 2.5 volts for 2 seconds (with RPM below 1600 and MAP < 70 kpa). It's possible it's not staying in the bad spot long enough to set a code.

But... It really sounds like the meter is giving that reading as it switches ranges. Does it have a way to override the auto range and lock it in to a certain range?

Edit: What if you hook the meter up with it at WOT, then slowly drop it back to idle? (Might cause the meter to stay in the higher range)

[This message has been edited by DRH (edited 08-05-2003).]

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kyote
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Report this Post08-06-2003 07:27 AM Click Here to See the Profile for kyoteClick Here to visit kyote's HomePageClick Here to Email kyoteSend a Private Message to kyoteDirect Link to This Post
My 86 was "stumbling" as well.. Only mine did it when I was going 50 mph or above. And it didn't do it all the time, just occasionaly, and it seemed like it was only when it it was up to operating temp. I swapped it out with the TPS on my 85, and it hasn't stumbled yet.

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stuartlowery
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Report this Post08-07-2003 02:40 AM Click Here to See the Profile for stuartloweryClick Here to visit stuartlowery's HomePageClick Here to Email stuartlowerySend a Private Message to stuartloweryDirect Link to This Post
 
quote
GM recommends using ONLY a DVOM to check any wiring going to an ecm system. You DEFINITELY have a bad TPS if it skipped like you said. Good luck.

This is for checking wires that are connected to the ECM not the DISCONNECTED SENSORS. A digital will jump around when it switches ranges. Une an analog on sensors use a digital on ECM connected wires. The analog meters send out voltage to check ohms the digitals do too but they send out less. A sesnor is usually nothing more than a varable resistor so an analog cannot hurt them.

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