D4D Maf Sensor

January 6, 2012

Hi all,

I'm new to this forum so forgive me if I'm going down a well trodden path. I have noticed my MPG drop a few points from circa 52mpg to circa 47mpg (all motorway runs) on my 2.0 d4d. I was also suffering from a sticking EGR (power loss), and have since cleaned this and got my horses back. But my MPG has stayed the samel. Last time this happened it was sticking brake calliper, but not so this time. I have borrowed a ecu obdII gizmo, and my MAF shows 1.3 lb/min cold at 950 rpm, this goes to circa 10 lb/min when accelerating on the motorway (pedal floored), and settles to 0.8 lb/min when warm and idling at 800 rpm. can anyone say if these are normal MAF readings?

many thanks

January 13, 2012

Update,

Maf sensor seems to compared with other diesels. wrt OBDII logs, however, MAP sensor seems to read low at 100KPA. Have removed and cleaned intake and ran a log file with the pipe to the sensor from the manifold connected and disconnected. The "load PCT " is always at 100%. Me thinks the MAP is faulty but at £130 a go don't want to commit. The MAP reads 121kPa when reved to 3k. The log file reads 225kPa with the sensor disconnected (obviously gives a engine management warning)

any thoughts from the experts?

January 13, 2012

haven't a clue about the MAF figures but it's normal for mpg to drop over the winter (& not just because you are using demister, heater/aircon more) & especially so on diesels.

January 14, 2012

Good Point Heidfirst, but have not notice this problem over the past 4 winters. OBD2 log files are showing that the engine is running continuously at 100 percent load. The ecu thinks i'm driving up a steep hill, and is compensating by adding more fuel. It would be brill if some kind avensis 4D4 2.0 owner could provide me with a good diagnostic graph/logfile of REVS/MAF/MAP/PCT LOAD, for comparison purposes.

My thoughts are still leaning towards MAP sensor (100 Kpa is near normal atmospheric pressure) or manifold problem i.e. Vac/turbo

Thanks for taking the time to comment, its very much appreciated.

January 14, 2012

Give the MAF a clean with electric contact spray ( OR CRC) and if that doesn't work change the MAF. The air filter is clean I take it?

January 15, 2012

Thanks for the advice Taff, I have removed and cleaned the Maf with contact spray, the air filter is less than a year old but will be replaced next week. There is still no marked difference, and I'm reluctant to Shell out for a new MAF sensor until i know for sure it is faulty.

Will try and link to my odb2 readings