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The mkiv Supra Owners Club

FBW Problem?


Markie

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Hi all,

 

Had the problem twice now. Car will start but engine management stays lit and even with pedal full on I get tick over revs.. Turn off and try agai. And things back to normal..

 

Any ideas?

 

Is there some FBW sender unit or something that can play up or go?

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Sounds like it's in safety mode...I had this before. Mine would go into limp home mode during a journey.

 

Although I never found what afflicted mine I'd say you need to get the OBDII codes read (if I recall correctly the vvti doesn't work with the pin shorting method of getting the codes).

 

I would expect that a sensor is not working properly. Or the Throttle Body needs stripping and cleaning.

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Would it be MAF sensor cleaning as well? Or do you think Throttle Body?

I was wondering if there is a FBW sender unit or something which is known to play up.

 

Thinking about it, the other day it did start reving higher than normal tick over when just left running for a few minutes.. Like as if the AC had been turned on.

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The VVT-i's electronics are more advanced and more interlinked...so I don't think anyone will diagnose it without the OBDII codes being read. But yes it could be the MAF...or the coolant flow...or the DBW TPS or the crank position sensor or a bad earth or....

 

Cleaning the MAF isn't really possible...too easy to damage it further I would guess, I don't know if anyone else knows.

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There's a redundancy pot (two pots) on the pedal, and a redundancy pot on the TB. One or more will be sending false signals to the ecu, either because a pot is faulty, a connector is faulty, or the loom is faulty. If the signal from the 2 pots don't agree the ecu sees trouble and goes to safety mode. FBW is a PITA.

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Thanks Chris... Any pointers of where exactly these "pots" are so I can do some basic checking?

 

How did you come to these units from the error codes.. They sound like two different things..

 

Ahh these things? throttle body potentiometer

 

I'd hope it's not loom :(

Edited by Markie (see edit history)
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One pair is on the acclerator pedal, the other pair on the throttle body. The "pairings" are in one housing. You *MIGHT* get away with a multi meter that reads Ohms and volts. Measure the resiatnces as you get someone to slowly press and release the acceleratotor. Also measure the voltages at the ECU (0 to 5 volts or very close), If you are not confident get someone who is to do it. You just *COULD* knacker the ecu. Google Motec webinars, and on YouTube, they may have a webinar on checking FBW stuff, not sure.

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One pair is on the acclerator pedal, the other pair on the throttle body. The "pairings" are in one housing. You *MIGHT* get away with a multi meter that reads Ohms and volts. Measure the resiatnces as you get someone to slowly press and release the acceleratotor. Also measure the voltages at the ECU (0 to 5 volts or very close), If you are not confident get someone who is to do it. You just *COULD* knacker the ecu. Google Motec webinars, and on YouTube, they may have a webinar on checking FBW stuff, not sure.

 

the accelerator pedal pots are on the throttle body and are operated by the throttle cable ( most cars that are DBW have the acc pots on the throttle pedal), first thing I would do is clean the multi plug on the throttle body, as I had problem with my car (supra vvti) sitting at the traffic lights when the mil light came on and lost the DBW control, which then only gives you about 1/4 throttle which you get from the throttle cable. I cleaned the multi plug and its never happened again. good luck and regards Chris

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