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Tech Area => General Buick Tech => Topic started by: Scoobum on April 03 2015, 05:47:20 PM

Title: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 03 2015, 05:47:20 PM

Got a call from Dan today and his car is running like crap...and the TPS via SM is erratic. Bad TPS?

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: earlbrown on April 03 2015, 07:21:49 PM

or wiring between the TPS and ECM.  Odds are it's the TPS.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 03 2015, 07:38:04 PM

Thanks Earl. Doing a Caspers order. Gonna get John to toss one in with the rest of the stuff.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: earlbrown on April 03 2015, 08:28:34 PM

It's always good to have a spare, but I'd back probe the one installed just to see.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 04 2015, 10:10:53 AM

Question. Dan picked up a modded ECM to run his old skool 83's. Is it possible that ECM is causing the issue? I have a known good ECM here I can try.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Steve Wood on April 04 2015, 11:44:59 AM

It can be......I have seen it do it once....you can also put a meter on the tps and see if it is giving you the same numbers as the scan tool

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 04 2015, 12:48:57 PM

Quote from: Steve Wood on April 04 2015, 11:44:59 AM

It can be......I have seen it do it once....you can also put a meter on the tps and see if it is giving you the same numbers as the scan tool

We both know I'm useless at electrical. :)  I'm assuming you want me to probe the ends of each of the three wires...and the value should stay steady.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: TexasT on April 04 2015, 01:42:40 PM

I believe the value should move as you open the throttle plate(the tps moves)
I think at rest it might be like .42v and at wot 4.5 or so and should move steadily as you open and close the throttle. If it jumps there might be a dead spot on the tps. I think you can read it on a scan tool also.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 04 2015, 02:05:14 PM

Quote from: TexasT on April 04 2015, 01:42:40 PM

I believe the value should move as you open the throttle plate(the tps moves)
I think at rest it might be like .42v and at wot 4.5 or so and should move steadily as you open and close the throttle. If it jumps there might be a dead spot on the tps. I think you can read it on a scan tool also.

Dan said with key on...the TPS value on the SM is jumping all over the place. It won't stay still. If you watch the TPS on PL you SHOULD see it move smoothly as you move the throttle. I'm gonna take my PL to Dans tomorrow and hook it up to this ECM I have. Figures the one spare part I don't have is a known good TPS.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: daveismissing on April 04 2015, 04:49:08 PM

Take a voltmeter and look at the wire that carries the 5v supply to the TPS -is that steady?

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 04 2015, 04:52:12 PM

Quote from: daveismissing on April 04 2015, 04:49:08 PM

Take a voltmeter and look at the wire that carries the 5v supply to the TPS -is that steady?

Will check tomorrow. Which is the 5 volt wire?

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: daveismissing on April 04 2015, 05:10:23 PM

When  you do what Steve asked you will have figured out the TPS and GND wires
So its the one left over...

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Steve Wood on April 04 2015, 06:06:37 PM

The dark blue wire is the signal wire :)

5.0v wire is the gray one

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 04 2015, 06:21:46 PM

Thanks Steve. I'll get at it in the morning. Gonna freeze my ass off in the 32F temps tomorrow.

Title: Re: Erratic TPS Reading And Running Like Crap
Post by: Scoobum on April 12 2015, 04:16:11 PM

Swapping in a known good ECM cured the issue. Thanks for the help guys.