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The mkiv Supra Owners Club

2jzgte hesitating under boost


jza800

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Aha, that's really bad :) If the vac reference hose wasn't on the stock FPR but it was still in place, it would form a constant restriction and therefore give a constant fuel pressure regardless of intake vacuum or boost pressure. The FPR fitted in series after that can only *increase* the restriction. I think, though, if FPRs work how I think they do, that means you'd mess up the vacuum fuel pressures as it can't ereduce fuel rail pressure, but not really affect the on-boost pressure - which is sort of the opposite to what the problem you have sounds like.

 

However you really are in uncharted waters having two inline FPRs, one of which has no vac reference. Who knows what kind of weirdness it would cause - hopefully removing this clears up your problem :)

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the stock fuel pressure regulator, was still connectet to the vacum line as stock.. so hose from stock fuel pressure regulator, to map sensor , they meet on a 3 line connector, so one side fuel pressure regulator, other side map sensor, and the last goes to the intake plenum. that was how it was fittet WITH the aftermarked fuel pressure regulator..

 

i hope too that fix my problem..

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Ian, with vacuum the regulator reduces the ignition on, engine off line pressure, (spring pressure in the regulator). Engine running with atmo on the reference line from the plenum the fuel pressure regulator still gives spring pressure, and under boost pressure in the reference line the regulator closes off the return hose and rail pressure should increase at a 1 : 1 ratio with boost pressure. The "Sputnik" damps out low RPM pulsations in the plenum, and also stops intake backfires rupturing the diaphragm in the FPR and MAP sensor.

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chris what do you mean with sputnik?? is it the gas filter you are talking about?? it is screwed in to the plenum?? and the map sensor and the fuel pressure regulator is connectet to it??

 

And do you think that with this aftermarked fpr, could be the problem??

Edited by jza800 (see edit history)
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now this is strange:

 

when the engine light is off, the car hesitating under boost.. but if the engine light is on, no hesitating at all under boost ???

 

the only error code i have is 42 speed sensor and comes after a couple off sec over 100 km/t or 62 Miles per hour

 

can it be the gizzmo ms-2 fuel cut defender that is my problem off the hesitating?? as i am thinking that when the engine light is on the engine goes in safe mode somehow. and the ecu dont take the voltage info from the gizzmo anymore.. because it have somekind off a safemap in the ecu and it run that nomatter what else others sensor is telling the ecu ???

Edited by jza800 (see edit history)
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Yes i now that and i will do, but that is only so i have a kind off understanding how the ecu work when the engine light is on?? because if it have a safe map in the ecu that activate when the engine light is on, and somehow close what other sensores are sending back to the ecu when it is in safemode, then it make sense that the car run normal with the engine light on, and hesitating when it is of because the gizzmo sends the wrong voltage to the ecu..

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Yes i now that and i will do, but that is only so i have a kind off understanding how the ecu work when the engine light is on?? because if it have a safe map in the ecu that activate when the engine light is on, and somehow close what other sensores are sending back to the ecu when it is in safemode, then it make sense that the car run normal with the engine light on, and hesitating when it is of because the gizzmo sends the wrong voltage to the ecu..

 

You're a budding "Gizzmologist". :D

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As far as I understand it if a sensor gives a wildly unexpected or out of range signal, or no signal at all, the engine light will come on, and a fault code will be logged. Does the light behave normally, as in it comes on when the ignition is at the key on, engine off position, then go out very shortly after the engine is started?

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yes, when the ignition is on the engine light is on, and goes out shortly after you start the engine, have now taken the gizzmo ms-2 fcd of, and put the wirring together on the ecu.. same problem as before.. only when the engine light is on, the car act normal..

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Are both ecu to engine earth tags bolted to the intake manifold? I have a feeling if the ecu is missing a ground it just *MIGHT* do something like this. DavidP once posted a photo of where the two eyelet tags should bolt. They can be felt for, but are hard to see with the engine in. As such, it's easy to forget to bolt them up if the engine has had the loom removed..

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and i can see on the air/fuel gauge that when it is hesitating/spark blow out or what we can call it, it goet out to lean, first it was on the right way to rich then the hesitating/spark blow out or what we can call it, the gauge go to lean 16.+ range about 2 sec, then the gauge did go back to rich 10.8 to 11.5, and it pull fine to redline with no problems at all..

 

but again, when the engine light is on, there is no problem what so ever, is pull like normal, and the air/fuel gauge goes to rich like i should..

 

so i really dont now what to do from here...

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