Maf sensor

[Almo2015]

My car as no power(runs poorly) when maf sensor is plugged in, if I unplug maf sensor car runs fine? Purchased new maf from europarts plugged it in no power? What can be the problem?

[Hell Razor5543]

It is not unknown for parts from ECP to be of less than optimal standard.

[Almo2015]

Didn't buy cheap maf sensor I bought Siemens one.

[myglaren]

Could still be a duff one, possibly damaged, have you had a look at the fine wires in it. If it has been dropped it is almost certainly kaput.
Odd that it is Siemens as they spun off that business to VDO some years ago now.

[Mandrake]

Check very carefully for air leaks downstream of the MAF sensor, especially tears/splits in any rubber intake ducting.

Any air that gets into the induction system after the MAF sensor is un-metered air, this will cause the injection time to be too short for the amount of air flow. (The engine runs too lean)

When you disconnect the MAF sensor the ECU can no longer use the MAF reading and will use a backup strategy to estimate how much airflow there is from engine RPM and other factors, so the engine runs "OK" in this partial limp state, (since it no longer matters if the air gets in past the MAF as it is not being used) but will not run as efficiently as normal.

If you can't find any air leaks you're going to need to do a Lexia diagnostics session to measure the MAF sensor output and check for any fault codes.

[Paul-R]

As it's an HDi most of the time it'll be under pressure rather than vacuum so air will escape out rather than in. This should mean that any mix will be rich rather than weak surely?

[electronmirror]

...but the MAF is upstream from the turbo so will be under vaccuum.

Downstream from the turbo will be under pressure and it's not unknown for splits to develop in the rubber pipe from turbo to the intercooler and intercooler to manifold.

Getting the car onto a Lexia will show exactly what the MAF is doing and prove whether the new one is duff or not.

[Paul-R]

Ah, my bad. Quite right, it's just after the air filter. I suppose what I was thinking of was exactly what you mentioned with splits in the hoses after the turbo allowing air out rather than in.

[Almo2015]

Thanks for reply chaps, I'll have a look at hoses for vacume leaks, also my car as no Egr solenoid it's been blanked off? Is this normal? Thanks again Sean

[GiveMeABreak]

Thanks for reply chaps, I'll have a look at hoses for vacume leaks, also my car as no Egr solenoid it's been blanked off? Is this normal? Thanks again Sean

It sounds like someone has previously blanked it off to avoid cleaning or replacing it. By their nature, they will ultimately need cleaning or replacing due to the build up of deposits.