Slipping transmission?

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Nordin

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Yeah, didn't understand that graph either. I suppose the vertical axis is TPS value? While looking at the graph or screen, press the gas pedal about 1/4 way and the TPS should be 25%. Ditto for 50%, etc. Should be pretty consistent.

Does your app allow you to record data? Go for a drive and then review information such as fuel trims. I'm certain a misfire will cause fuel trims and O2 sensor to show some spikes or dips of some data. At least it will hopefully give you an idea if the problem is on bank 1 or bank 2.
Going to test that tomorrow, both press de gas a quarter, half and full.

Yes it does record data, will do a recording and get back to you, doesnt understand that much of fuel trims and O2 sensors to be honest, or atleast not the readings from them.
 

Schurkey

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Why would he use a voltmeter when he has a scan tool to draw a graph?

That's like starting a fire with a flint and a steel, when you have a working Zippo in your pocket, and a flask of vodka on your hip.
 

GoToGuy

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So as you describe normal acceleration to highway cruise speed. As it attempts to shift to overdrive, it hesitates as in not shifting to overdrive or is it an engine miss? Have you test driven same way process, except drive using 3rd hold versus normal D drive? Does it react the same way? Did you mention what year and engine size?
 

GoToGuy

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Your graph appears to have time and voltage value. Can you change display to voltage only real-time. Then depress throttle idle to wide open in 5 seconds and watch voltage smoothly increase. No gaps, zero indications. Then same in reverse. There have been reports of TPS failure in position where it holds same position long periods as in highway cruise. Just one of many causes to drill down to find failed part. Good luck.
 

Schurkey

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can you make any sense of that graph at all?
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That graph?

Looks to me that there's either noise on the signal wire, which would cause problems all by itself; or someone was tapping the gas pedal now and then.

If you had your foot OFF the gas pedal, I'd re-run the test. Any more spikes like that--especially combined with the engine running goofy at the same time--and I'd be looking for reasons that the TPS or it's wiring harness is transmitting contaminated signal.
 

tinfoil_hat

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Maybe try driving in 3 so it won't shift into OD. See if it still happens. I had a problem with my old burb with the 700r4 that turned out to be a torque converter problem. A few seconds after shifting into 4th it would vibrate like I was driving over a washboard road. Not sure if that's what you are describing but it's an easy thing to rule out.
 

udidwht

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Why would he use a voltmeter when he has a scan tool to draw a graph?

That's like starting a fire with a flint and a steel, when you have a working Zippo in your pocket, and a flask of vodka on your hip.
Due to the fact he already was having issue understanding what the graph was putting out. A volt meter is simplicity. Starts at .5 and goes to ~ 5 volt (watch for smoothness)
 

honkon

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Due to the fact he already was having issue understanding what the graph was putting out. A volt meter is simplicity. Starts at .5 and goes to ~ 5 volt (watch for smoothness)
I think if this guy can't understand a simple XY graph he should take this truck to a reputable shop.
It's easy to hook up a scanner to the diagnostic port and have a computer draw the graph for you. You could even do the test sitting inside with the engine running and AC on.
Much preferred to test components without touching them at all...
 
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