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The mkiv Supra Owners Club

Dirty Map / Maf sensor?


how_supra

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The MAP will not get dirty, its just a pressure sensor that's connected to the manifold. Fitted to J spec Supes.

 

The MAF sensor on the other hand is either a hot wire or thin film sensor, fitted to UK spec.

 

If it gets dirty (due to crud getting through the air filter and burning onto the hot wire or depositing on the film) then it will start to under read (as it won't sense the air flow past it as the crud acts like insulation).

 

This will make mixtures go lean outside the range that the oxygen (lambda) sensor works in. This will mainly be at the higher power levels.

 

When it really goes bad the ECU will flag up an air flow error and give the check engine light and the warning triangle.

 

The effect isn't usually much, with a variation of about 5% between new & worst crudded MAFs. Still, its enough when you're running close to detonation.

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