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The mkiv Supra Owners Club

Fuel cut problem


Parry_10
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hi, I have a tt bpu and im hitting fuel cut at around 5000rpm

 

I have a 2inch ristrictor ring and I have a hks fuel cut defender on setting 9 and when I hit fuel cut im hitting around 1.1-1.16 bar of boost and have my boost controller set to a max of 1.25bar.

 

I have a hks sqq bov and the sound of the air releasing to the atmosphere changes sometimes I get a chattering sound- dont know if thats of any relevence

 

anyone got any ideas?

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really? I have ngk bkr7e plugs in mine. and it only happens on high rpm and for a couple of seconds, definatley seems like fuel cut to me as the engine light comes on whilst it does it as well and then I get an error code for turbo pressure malfunction

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If the engine light is on it does sound like fuel cut, mines wasnt doing this just hesitating (slight misfire) which was down to having the wrong grade plugs in when i bought her - smooth as a nats butt now - good luck getting it sorted mate.

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really? I have ngk bkr7e plugs in mine. and it only happens on high rpm and for a couple of seconds, definatley seems like fuel cut to me as the engine light comes on whilst it does it as well and then I get an error code for turbo pressure malfunction

 

Fuel cut is like hitting a wall, the engine will suddenly lose all power for a moment, a misfire you will hear/feel as a series of misses, not a sudden cut in power.

 

When the boost is raised to 1.2bar you need to fit a cooler grade of plug or reduce the plug electrode gap to prevent misfire. See Spark Plug FAQ for more info.

 

If it is a misfire (and not fuel cut) and new plugs doesn't cure the problem then the other cause could be the coil pack connectors, overtime the plastic connectors become brittle and disintergrate from the engine bay heat which can cause misfire. See coil pack connect refurb guide HERE, if yours haven't been done then I'd do them at the same time as fitting new plugs.

Edited by Nic (see edit history)
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Very good post as i was confused when i got the slight hesitation from having the wrong grade plugs... really did think it was fuel cut!

 

It's easy to distinguish between fuel cut and a misfire once you have experienced both.

 

Fuel Cut - ECU receives signal of >1bar from the MAP sensor, it cuts ALL fuel to the engine causing complete loss of power.

 

Misfire - 1 or more plugs causes a miss in 1 or more cylinders, this is felt/heard as a hesitation in the revs. A misfire is usually caused either by worn/wrong plugs or broken coil pack connectors, symptoms usually only occur at high rpms/high boost, the car can run fine at lower rpms/boost levels.

Edited by Nic (see edit history)
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I'm glad you brought this up and thanks Nic for putting a link to refurb the coil pack connectors... I had this problem prior to deploying. Now I should be able to get her running smooth, along with new wires and spark plugs since I don't know the last time it was done, before shipping her off to the UK. Many thanks!

Edited by LolaBoost94 (see edit history)
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