Unstable TPS signal, Brain MS2, so cannot setup boost control. - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-19-2012, 01:07 AM   #1
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Default Unstable TPS signal, Brain MS2, so cannot setup boost control.

Hey guys,

Got the car all up and running and the TPS working, but the issue is that the tps signal is not linear.

I set it using TS, and its wired to increase with throttle.

What happens is usually I get no TPS % until a couple centimetres of throttle, and then it starts slowly, and jumps to 100% (or 121 or 117 % or watever it feels like on the day) after 3/4 throttle.

Ive verified that the TPS infact works correctly and gives a stable linear reading on my multimeter.

Any suggestions?

Thanks,
Dann

Last edited by nitrodann; 02-19-2012 at 01:19 AM.
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Old 02-19-2012, 02:19 AM   #2
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Check the signal on the harness between the tps and the ECU. I had similar issues, which ended up being a bad wire in the harness.
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Old 02-19-2012, 02:42 AM   #3
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Yeah I just noticed that the signal is jumping around a bit in tunerstudios, as in, If i recalibrate closed throttle 5 times I get 5 different results, and i can physically see the blue bar jumping around.

And now it wont connect at all.

Thanks,
Anyone else have anything to test?

Dann
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Old 07-05-2012, 08:59 AM   #4
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I have the exact same issue with my car. Did you find a solution?
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Old 07-05-2012, 09:21 AM   #5
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I'm pretty sure you guy are using the stock 90-93 TPS, not a true linear TPS.
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Old 07-05-2012, 05:33 PM   #6
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I haven't been running the stock TPS for a few years.

Currently trying a NA8 TPS but I've been using NB8 TPS's previously.

TPS is wired according to the instructions on miataturbo. Are these instructions incorrect?
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Old 07-07-2012, 08:04 AM   #7
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I had a problem with mine that drove me ------- bonkers until I figured it out - granted, my setup was a bit weirder (94 car, 99 tps + tb) and trying to mix and match instructions didn't help me until I sat down and walked through it.

Just for fun - here's a graph of wired correct vs wired incorrectly looks like.



And my quick and dirty test rig..



But yes, I did try reading the various "how to tell how to wire" threads. And I'd recommend swapping your vref and signal lines, keep your ground the same - I think that was what my miswire turned out to be.
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Unstable TPS signal, Brain MS2, so cannot setup boost control.-img_20111205_012714.jpg  
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Old 07-07-2012, 11:20 AM   #8
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Spot on Bittetech,

I actually solved this a few hours ago with the help of another turbo MX5 owner in Brisbane. He encountered the same issue following the NB TPS instructions on this site.

At his suggestion swapped Vref and TPS signal and it's now working fantastic!

I'm running a BP motor in a NA6 shell with NB TPS now.
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