Failing airflow meter on V70 TDI - Symptoms ?

I have a 1997 2.5 TDi V70 (diesel), approx 168,000 miles, and wondered what
the symptoms are if the mass air sensor is failing.
Do they get dirty and need cleaning ?

Thanks,
Nick

 

a failed or dirty MAF usually gives the symptoms of the engine goes flat
just as the turbo spools up- a lack of power over say 2500-3000rpm.

If unplugging it brings back 85% of the power, then replace it.

Yes, but cleaning is often short lived.

Also always replace it with the genuine Bosch article. The cheaper ones are
cheaper for a reason...

Tim..

 

Hi Tim,

Sounds like it may be what I have - around 2300 to 2700 rpm it is hesitating
as if the "mixture is wrong"

Does this sound like it could be the MAF ?

Thanks,

Nick

 

Nick as I said, the usual symptom is a lack of power under load when the
turbo is spooled and creating extra airflow- the MAF is not signalling to
the ECU that this is happening, so it underfuels. A clean exahust is also a
sign - i.e. no trail of soot under hard acceloration.

Tim..

 

OK - thanks for the reply..

I don't think I have underfuelling unless it occurs just at this rpm are..
it seems quite "pokey" at WOT and higher revs,
although I don't seem to get a visible exhaust trail, just a bit hesitant
around 2500 rpm and light throttle..

Thanks,

Nick

 

Ahh!

Then check the TPS and more likely the EGR valve. (preferably blank it off
alltogether)

Tim..

 

I have heard about blanking off the EGR but also rumours that some
damage might occur, so I haven't. If the only negative might be that
under some conditions the emissions might be a tad worse, then I am
OK about it, but I don't want to overheat or in some other way harm
the lump.
I guess the TPS is just a pot and a multimeter across the terminals
to check for smooth / progressive operation is what needs to be seen
?

Thanks,
Nick

 

No harm at all, infact usually more responsiveness at smaller throttle
openings, better MPG, less soot, and alot less bunging up of the intake
system with soot, that you have to clean out.

Yes- exactly.

Tim.
..

 

Great ! Thanks,

I will have a go later then.

Nick

 

Will blanking the EGR off cause the Check Engine light to come on?

THNX.