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Discussion Starter · #1 ·
Before you give me the obvious answer...

That it switches at a point barely off full closed throttle, and switches again at WOT...

Just what happens when it does those ?

ie: the middle wire on the switch is power. (Blue w/ red)


The top wire and the bottom wire get power only when the switch is in the fully closed, or WOT positions.

So what happens when the top wire gets power ? (Fully closed throttle)

What happens when the bottom wire gets power ? (WOT)
 

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From the manual, kind of abbreviated where possible to shorten the post:
The TPS is connected to the throttle shaft and is a potentiometer with one end connected to 5 volts from the ECM and one wire to ground. A third wire is connected to the ecm to measure the voltage from the tps. At a closed throttle the output of the tps is low, about .48 volts. As the throttle is opened, the voltage increases until it reaches about 4.5 volts at wide open throttle. By monitoring the output voltage from the tps the ecm can determine fuel delivery based on throttle position (driver demand). A broken or loose tps can cause intermittent bursts of fuel from the injector and an unstable idle as the ecm will think the throttle is moving. Hope that helps.
 

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The 2.8L uses a full potentiometer and changes the voltage the ECM sees from idle to WOT. But the one for the 2.6 looks like it just tells the ECM when it has reached idle or WOT but nothing in between. At idle it will reduce fuel and maintain the desired idle speed and keep timing up. At WOT it would go into fuel enrichment mode to richen up the mixture to make the most power possible.
 

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I'd imagine that since the I-TEC engine has a way of telling how much air is entering the engine real-time, regardless of throttle position (mass airflow sensor), the only thing it needs to know is when the throttle is fully open or fully shut.

Unlike the GM TBI system, where the exact position of the throttle butterflies is a very important piece of info for the ECM.

Cheers........ed
 

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Did you get the memo that were putting the new cover sheets on all of our TPS reports?
 

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stusvend said:
Did you get the memo that were putting the new cover sheets on all of our TPS reports?
damn. beat me to it
 

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PolarStar said:
stusvend said:
Did you get the memo that were putting the new cover sheets on all of our TPS reports?
damn. beat me to it
Well, you know. Great minds and all. :D

love that movie
 

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Discussion Starter · #8 ·
stusvend said:
Did you get the memo that were putting the new cover sheets on all of our TPS reports?
???
 

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Selador said:
nfpgasmask said:
Selador said:
stusvend said:
Did you get the memo that were putting the new cover sheets on all of our TPS reports?
???
Really? Office Space? Its a classic.

Bart
Never watched it.
Oh please do yourself the kindness then and give it a couple hours of your time. Well worth it.
 

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I just..........just........just want my stapler. Has anyone seen my stapler?????? :confused2:
 

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Discussion Starter · #14 ·
nfpgasmask said:
If you have ever worked in an office environment, this movie hits the nail right on the head.

Bart
But it doesn't do a damn thing for the TPS. :wink: :wink: :wink:

So apparently...

As I said above, this TPS is simply a double switch. Switches at both WOT, and throttle completely closed.

I wondered where the 'signal' went from there, and why.

I think Betterthanyou pretty much hit it on the head. It goes to the ECU. Which then decides to either cut the fuel down a bit, or add more, depending on whichever end of the throttle cycle it is on.

On mine, the bottom end is "switching" at a point that is "into" the throttle pedal travel by a bit. Just far enough in, that it is in the middle of the "sweet spot" that I use, when coasting along at any given regular speed.

Causing it to act like I have stomped the brakes, every time it goes below, and then act like I stomped the gas, the instant it goes back above.

I wondered why it would act like that. The 'goes into idle mode, and turns the gas delivery down', pretty much answers that question.

If the engine is all of a sudden, trying to "idle", (which is generally 900 to 1000 RPM), and I am coasting along at 2400 rpm at about 55mph... Then it is like using the clutch and engine to "brake" the vehicle with.

Go that thousandth of an inch back up, and it suddenly has all the gas and rpms it needs at that speed.

I pretty much knew that was happening. And knew the cause of it. I just wanted to understand the "why" of it.
 

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Discussion Starter · #15 ·
Well, I hope I haven't spoken too soon.

I just finished 'adjusting' the TPS again, and I swear that thing was already adjusted correctly.

Maybe it is something else causing the jerking backward and forward ? It just seemed logical that it was the TPS. I mean, let it down past that certain point, and the truck very seriously nose-dives like it is 'clutch-braking'. And the only reason I can think of for that is the ECU going into 'idle' mode.

Well, if it remains as bad as it was, I'll replace the TPS.
 

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According to the book...

-When the idle switch is closed at a high enough speed the ECM enables deceleration mode and reduces the injector pulse width to save fuel and prevent afterfiring.
-When the switch moves off idle while the engine is cold, the ECM provides transient enrichment.
-When the WOT switch is closed the ECM goes to an enriched open loop mode.
-When the WOT switch closes while the car is moving AIR injection will turn on for 10 seconds to oxidize exhaust gasses from the enriched misture
-When the idle switch closes AIR injection is disabled for 2 seconds to prevent afterfiring
-Supposedly there's some impact on ignition timing, probably to control idle timing
 
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