What should my MAF sensor read?

[nealegray]

I'm hoping someone can shed a light on if my MAF sensor needs replacing.

My car started idling very badly the other day travelling from Brighton to North Yorkshire in the inevitable hold up on the M25. I was only half way there but still managed to drive the remaining distance and then back again a couple of days later. The car runs fine at higher revs its just idling and at lower revs that its a problem.

When idling, the revs drop to around 800 rpm then increase to around 2000 then drop again. Looking at other posts I think it could be the MAF sensor. I have a draper diagnosis tool and have the code P0171 System too lean Bank 1. The draper tool allows me to track the MAF output I get the following readings.

RPM MAF in g/s
800 8 g/s
1500 15 g/s
2000 20 g/s
3000 23 g/s
4000 34 g/s
5000 43 g/s

Do these readings look right? I cant find any list of the MAF readings other than peak readings for you guys with modified engines. I should maybe say that the car was stationary when I did this and the air filter was disconnected, I dont know if that would make any difference to the readings.

The car is a standard Leon Cupra 240bhp.

Any help greatly appreciated.

 

[mty12345]

Sounds pretty high at idle. Usually closer to 3g/s would be a normal reading for an engine of that size.

This may be of some help.

https://www.alldata.com/sites/default/files/file-attachments/maf_sensor_testing_110918.pdf

I would check all the intake and vacuum system for leaks before condeming the maf, and if you replace it then make sure you buy a bosch one from a reputable source.

 

[nealegray]

I might have found my problem. The other failing part that seem to commonly come up is the PCV valve. On another forum someone suggested removing the pipe from the Inlet maniford to the PCV valve and capping it off, then seeing if the idle problem reoccurs. I removed the pipe from the PCV valve swung it around so it was accessible with the engine cover on and started the engine. The pipe is a vacuum line so I just sucked the lid of an oil bottle onto the end and my car is now idling perfectly.

So it looks like I need a new PCV valve.....

 

[mty12345]

Yeah vaccum leaks can cause all sorts of idling issues.