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AFM problems - I think?

caminperth

By caminperth,
in Western Australia

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caminperth Grand Master

caminperth

Posted
Posted

Hey guys - got a problem to report - wondering if anyone can help out.

Last night me thinks - it's cold, 0.9 bar is going to be waaay safe so I dial it in and plant it in fourth. At this point a few things happened - which have happened before:

first boost comes up - ok, all good

then suddenly everything cuts completely for about half a sec - felt like I'd turned the key off!

then it cuts back in...

then it misfires around 5000rpm - which I'm guessing is the plugs and I'm hopefully going to fix that problem today...

the first problem of the engine/revs cut I'm thinking is the AFM going past it's voltage limit and shutting down.. does this sound right? what can I do to fix it? I've sprayed/cleaned it with heaps and heaps of electrical cleaner which didn't seem to make much difference..

Any ideas?

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DanielGTST Apprentice

DanielGTST

Posted
Posted

Caminperth,

I had the same thing happen to me when I had my car at about 13psi while mucking around. It was fine on the dyno but as soon as it was on the road it would start to have the problem you described.

The guy told me that it would be even worse on a colder day due to the fact that there was too much air getting into the engine and the air/fuel ratios where not adjusting correctly on my stock ecu.

A SAFC would probably fix your problem, I have a simple Pivot air/fuel meter (1 universal setting) and adjusted it to make it a little bit leaner and it has fixed the problem for me.

I am no mechanic/tuner so it is just a suggestion ;)

Daniel

caminperth Grand Master

caminperth

Posted
  • Author
Posted

aidwin - as you said man - it's not the speed cut..

b005t - yea - i know what the speed cut is like and this ain't it. :rolleyes: and yea - am still running stock cooler...

adrian - could be - but it's fully intermitent..

bam - i wish i could afford the gtr!

daniel - i've got an afc and itc (old skool apexi fuel and ignition controllers) and that should sort out the fuel issuses at higher boost...

i fixed up the plug issue today - tho can't really try it out in this weather.. :)

still at a loss as to what it could be.. still got an inkling it's the airflow meter maxing out... will do it more when there's cold weather due to more air due to the density change... sound right?

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
Posted

Cam,

It's the boost cut/fuel cut. The boost controller has nothing to do with it, it's the AFM that tells the computer when it senses too much air flowing, which means too much boost, and it will hit boost cut, resulting in a nasty sudden halt to the car:D

You'll need to replace your ECU or get a fuel cut defender to stop this happening. It is worsened by the fact you have a stock cooler, and cold air is denser, thereby the AFM senses more air flowing:D

Hope that made sense (and is true)

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