Last Lemming

So I’ve been trying to track down issues I have been going wide-open throttle. I have the Vitesse racing MAF and MoMonitor, so I’m able to monitor several variables of the engine performance as it’s running.

What its logging is this: the throttle is closed at idle, but as soon as I engage the accelerator pedal, even a little bit, it shows a wide-open throttle condition on the MoMonitor, However the throttle plate is barely open. But if I open the throttle to wide-open throttle, the computer says it’s WOT but it’s showing the throttle plate still closed.

my TPS tested within spec at the throttle body, so that leads me to believe it might be the wiring or the connector off of the wiring, however, I have no idea how to test this how does one go about testing the wiring for the TPSC if it’s good or not?

is it possible for a TPS sensor to test good but yet still be bad?

orig944

I have no idea about the things you have put on your engine, but I have a few of questions to clarify for others more knowledgeable.

1) Does the equipment you added look at the throttle position switch, which only indicates throttle closed or throttle not closed?

2) Was the restrictive air flow meter flap removed from the intake path, and therefore the airflow meter itself? (Otherwise, why would you change to a MAF!)

3) Did you do your testing with the engine running or not? If not, and no airflow meter input, the zero airflow over the MAF would tell the "MoMonitor" that the the throttle is closed.

walfreyydo

You may want to check the settings in your Vitesse. I know in Megasquirt there is a setting to change from a binary TPS to variable TPS. Not sure if something similar exists within Vitesse? You verified the voltage coming out of the TPS is variable correct? What about the voltage for TPS at the DME plug, still variable? This would eliminate wiring (or bad TPS) as the possible issue.

PS - I saw in your other thread that the part number on the TPS confirms it is in fact the correct variable TPS for the 944 turbo, so it appears the TPS you have is correct, I think the question is why is Vitesse seeing it as binary.

Last Lemming

I can’t say I understand the how it all works exactly, and I don’t know if the coding is binary or not, but the system has a MAP sensor you wire to the DME, so, even if the TPS sensor is binary wouldn’t all the control of the air and fuel be controlled by the MAP sensor?

walfreyydo

I am not familiar enough with Vitesse to know what things the TPS has control over, but on megasquirt variable TPS is used for (better) Accel enrichment (over MAP based) and other controls such as over run fuel cut, launch control and others. Its not 100% needed but if Vitesse is thinking the TPS is variable and using that input for some of its controls, I see how it could cause problems. However, I have no evidence to suggest this is the issue why the car is stalling on decel, just a hunch, and figure its something to check.

Vitesse should have some sort of cable to connect to a computer and there should also be some matching software that can interface with the Vitesse ECU to do all the tuning and so forth. Unless I am misunderstanding all of this and you are just running some soft of MAF kit, but my understanding was that Vitesse is a full standalone system?

Are you running the VRT8x?
http://www.vitesseracing.com/

There must be some sort of software download and user manual which walks through this but dont see anything on the site.

fast951

The Vitesse MoMonitor reports the status of the TPS (and other sensors) as the DME processes the sensor(s).
THe TPS should go from IDLE to PT to WOT. If you are going from Idle to WOT, then something is off. The TPS status wording is displayed on the screen. Check the status with the engine running.

If you are going from IDLE directly to WOT then there is something wrong. It can be the TPS, Wiring, even (on the 951) the KLR or KLR chip. Isolate each to determine the root causemof the problem.

As a side note, and not saying this is the case here. I have experienced a TPS functioning 100% perfect when cold, bit once hot it acted up.

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Last Lemming

I’ve been working with John (Vitesse) to sort my issue and he has been more than helpful.

He informed me early when trying to sort this issue that what I could be experiencing is a boost leak. I thought I checked this thoroughly, but it turns out I did not!

When driving the other day, when boost was at its highest, I heard a woosh right before power cut out. Sounded like a pipe let loose. And sure enough the soft hose coming off the turbo could be pulled off with my hand quite easily. The hose was very soft and apparently very old. Go figure, a 30+ year old car would have old parts on it. Haha!

so I have a new hose coming to sort that out and I think the issue will be solved!