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Maf signal drop to zero and surges at around 38% throttle

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Hey Guys,

I have a 1978 Torana that has come to me with an LS 6.0 litre fitted. I did not fit the engine but am trying to get it sorted.

The issue it has is at 38% throttle the Maf sensor reading goes to Zero, the revs drop MAF reading returns and it cycles like this until the throttle is below 38% or so. More throttle makes no difference. To the best of my knowledge the vehicle has not been tuned only the VATS and some codes turned off. The vehicle also experiences a flat spot on sharp throttle inputs.

A spare maf sensor fitted made no difference. Maf unplugged it runs better but I suspect that is because going into limp mode.

I have not checked fuel pressure yet as it seems to cyclic for a fuel issue. I can check that though.

Difficult to road test to confirm fault in gear but owner states it does it on the road. (car is not street legal)

I am not aware of an engine protection that needs to be turned off and the report of the same occurring in gear makes me think it is not engine protection.

Happy for any input and will provide results of tests if necessary. Tune file and log attached.

Thanks

Attached Files

HI Guys,

For anyone interested I found the cause of the issue.

Clearly at some time in the past someone had been playing around in the Map. The high frequency table for the MAF sensor had been filled with zeros.

Ever time the airflow when from low frequency to switch to high the ECU would read zero and cut fuel.

Found the issue by using the compare map feathers in HP tuners.

Hope this helps some one some day.

Darren