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AFM Failure - Weak mixture on boost

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Old 26 November 2005, 08:09 PM
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wintn
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Default AFM Failure - Weak mixture on boost

Looking at previous threads on the topic I got the impression that a faulty AFM affected the idling/slow running. Beware that it can give a very weak mixture on boost with no other apparent symptoms. Idle and general running was smooth.
This was confirmed during my Tec3 remap (at Powerstation) last week and they had to fit a new one.
Could be nasty if you persist in booting it and don't notice the AFM reading (or don't have one). You should notice that performance feels weak though, also improved fuel consumption.
Old 26 November 2005, 08:12 PM
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ALi-B
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Yes, this is often the cause of melted pistons, amongst other detonation related failures as it is under high boost conditions where lean mixtures can cause these failures. The bain of post MY98 scoobs.
Old 26 November 2005, 08:29 PM
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wintn
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I forgot to mention this, the strange thing is I have a Knocklink and it showed virtually no activity (yes it is working, lots of activity before AFM went and some after replacement and remap). I would have thought weak mixture/overheating would have caused det?
Old 26 November 2005, 08:34 PM
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It can, but the ECu will compensate and retard the ignition. But you still have higher combustion temperatures. And this would not nessecerily show any drastic rise in coolant or oil temps
Old 26 November 2005, 08:36 PM
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Originally Posted by ALi-B
It can, but the ECu will compensate and retard the ignition. But you still have higher combustion temperatures. And this would not nessecerily show any drastic rise in coolant or oil temps
Thanks. Still sounds like a trap for the unwary.
Old 27 November 2005, 11:19 AM
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Andy.F
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Originally Posted by wintn
I forgot to mention this, the strange thing is I have a Knocklink and it showed virtually no activity (yes it is working, lots of activity before AFM went and some after replacement and remap). I would have thought weak mixture/overheating would have caused det?
Normally a failing maf would cause increased knock activity until the ecu pulls the timing back. You will still run lean though, unless the ecu switches to the hi det fuel map which will only happen in extreme cases.
After your new maf and remap you should have no knock activity. (by no knock I mean no more than green leds)

Andy
Old 27 November 2005, 11:38 AM
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Thanks Andy, yes I only get the odd 1st or 2nd green in mid range after remap.
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