Possible MAF Failure?

[whitenemesis]

Recently noticed car seems less responsive to throttle at low revs, then surges at around 2000rpm. Gear changes are less smooth and seem to be hesitant, sometimes hunting if held at around 2500rpm.

Starting, cruising and mpg unaffected just the seems reluctant to pick-up from lights and junctions.

Car going in for MOT on Saturday and I have mentioned this problem, dealer says they will check it out but "forewarned is forearmed", so any advice greatfully received!

 

[Baron_Samedi]

Have you tried disconnecting the sensor and seeing if it makes any difference?

 

[BlackC55]

Don't disconnect the sensor as this will produce a fault code. Get it read on a Star and see what comes up.

This seems like a MAF issue but it could be other things too, like split vacuum pipes etc.

 

[Baron_Samedi]

<gets coat and heads for door>

 

[Dieselman]

Meter pin 5 on the MAF. Expect ~2v at idle rising to ~4.8v at full chat.

 

[stevesey]

<gets coat and heads for door>

Disconnecting is a normal diy check, but if the cars going to the dealer on Saturday you don't want to confuse the issue with false stored fault codes.

 

[racall]

As ollie said check those vacumn pipes.Mine was rubbing on a metal pipe and had a small hole in it.

 

[whitenemesis]

As ollie said check those vacumn pipes.Mine was rubbing on a metal pipe and had a small hole in it.

Did you get any air noise with the leak? I have a second (and perhaps quite possibly related) query

 

[BlackC55]

A split boost hose is a distict possibility. You get a whooooshing noise when accelerating hard under full boost.

 

[welland99]

What does MAF stand for?

 

[BlackC55]

Mass Air Flow (sensor)

 

[whitenemesis]

Update

MB Tech phoned to ask if I could bring the car in today ahead of the MOT tomorrow so he could have a quick check on the running problem...

He took it for a quick blatt down the service road and straight into the workshop. 15min later he handed the keys back..

Top marks to Olly and racall, it was a split intercooler pipe! Pipe replaced FOC and 5min later I was giving the car an "Italian MOT" to clear the system of unburnt fuel (caused by the split fooling the ECU into over-fueling).

Car drives as new now! :bannana:

Another example of excellent service from MB Swindon

MOT tomorrow but Service-Plus will take care of that

 

[BlackC55]

Do we win a prize?

 

[whitenemesis]

Yep! The pleasure of my company on the 16th May

 

[BlackC55]

ha ha.

See you then.

 

[whitenemesis]

I'm looking forward to it, always a great day out

 

[zishan03]

Hi Guys,

I am having the EXACT same problem. Any chance you could post a picture of the pipe they changed so I can check it over myself?


Thanks in advance.
Zishan

 

[BlackC55]

Look at the rubber pipe that goes into the EGR valve/inlet manifild.

 

[racall]

Mine was a small half inch rubber pipe that runs from a small round plastic thingy to the turbo on the left side front of the engine.It was chaffing/rubbing on a small black metal pipe.

 

[whitenemesis]

The MB tech removed the pipe during the emission test in the MOT to demonstrate the effect the split would have whilst I had been driving.

OMG!! the black cloud that came out of the exhaust was unbelievable!!