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Discussion Starter · #1 ·
I am dealing with a K20A2 swapped Fiat X1/9 that returned to the shop with apparently a bad TPS.

What I have done:

Checked wiring continuity between TPS connector and ECU pins. All good.

Swapped whole TB with a presumed good unit from another car. Car runs fine.

Replaced TPS with new. Ran great for the 80 miles I have driven it. Boss drove it today and it freaked out.

The reason I still suspect TPS is that, as you see in the screenshot, MAP indicates that the engine is under steady load, but TPS sporadically goes to zero. When this happens, mixture spikes lean and injectors apparently are being shut down.

As I said, I checked wiring continuity from end to end. Should I suspect bad wiring or a bad new TPS?

**DEVELOPMENT**

Swapped presumed good TPS back into car and it acted up again. Datalogs show that I am losing TP signal, but a bad original TPS, a bad new TPS and a bad used OE TPS from another car all together seems far fetched.
 

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Discussion Starter · #2 ·
Here is a screenshot whose resolution I can't seem to fix.

At this point, I am led to suspect the wiring between the TPS connector and the ECU connector, even though I already checked it and it showed good at the time I checked it.
 

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Discussion Starter · #4 ·
I can do that, but the MAP signal is smooth in the datalogs. Every time I experience the hitching, the TP signal is zeroing out. At times I am in steady acceleration, say 15% TP, the TP signal drops out to zero, then, since the ECU thinks the throttle has closed, the ECU turns off the injectors and injector duty goes to zero.

Should I still play with the MAP sensor?
 

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My best understanding is the TPS and MAP work with one another. I agree with your statement but if the extra parts are around....I would definitely try it.

Edit: what the volt reading on TPS at closed AND wide open throttle? (key to "on" position but motor not running)
 

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Discussion Starter · #6 ·
Yes, together they are the ECU's load sensing input, but they are discrete circuits.

Has anybody had weexperience with bad solder joints on the ECU? KPRO here.
 

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Discussion Starter · #8 · (Edited)
Regarding TPS voltage, across which pins?

Preliminary answer is that KPRO shows 0% at closed and 102% at WOT on a factory sensor and TB from another car tthat I threw onto this one as part of the diagnosis. The new replacement TPS is 0% and 100%. If you think voltages will be more informative, I can do that as well.
 

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Discussion Starter · #9 ·
**Update**

Installed stock A2 ECU with K-Tuned immobilizer bypass. Car runs fine. This is not conclusive evidence of anything considering how this problem has disappeared and reappeared, but if the ECU solves the problem, then the fault must lie in the KPRO. Has anybody ecer had a bad one?
 

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Try the Kpro in another car, that should rule it out or confirm it.
 

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Discussion Starter · #13 ·
Hondata's customer service line might as well be an automated "EPH YOU!!" followed by a hang-up. I have zero positive experience with their customer service.

I will check the voltages.

I cannot install the KPRO in another car. We are a Fiat shop, and I only have one K20'd X1/9 running at a time. The next one is a couple of months off from being together.
 

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Try recording tps values in kpro?

You established the harness is good so I would guess next that there is bad connection at connectors on either end but you changed the ecu and the car ran fine so I would then make the assumption that the kpro ecu side connector needs to be checked inside and out. Bad solder joints are not obvious.
 

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Discussion Starter · #15 ·
I found that some of the TP connectors on the ECU end of the harness were not tight enough to make good contact with the ECU pins. I tightened the connectors a bit and the problem was solved.
 
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