Whilst driving my 04 BCGT this morning, it felt a bit uneven on idle. Still drives ok, just a bit lumpy. Got home and plugged in the OBD Reader and it came back with one code, namely P0102. Mass or Volume Air Flow A Circuit Low.
Any suggestions or advice would be gratefully received. Thanks. Beo.

 

There are a couple of possibilities with a P0102 On the early W12s in Bentley. Check these first before you replace the MAFS.

Most common problem is an air leak somewhere past the MAF. A common cause is one of the 4" tubes has slipped off one of the charge air coolers.

Second most common problem is a bad MAF connector. The RS/primary MAF is a 4 wire; the LS secondary is a 5 wire. There is an improved replacement connector that is a heavier gauge pigtails with better connector contacts. I've replaced both of mine with the newer ones.

If neither of these works, then it could be a MAF going lazy or defective. You could first try cleaning both with an Electronics contact cleaner as sometimes a dirty MAF will not produce a constant Hz signal throughout the RPM range . But if you decide a MAF is bad it is better to replace both, not just the bad one.

 

Any update?

Let me add a little as I am guessing you do not have a permanent MAF issue, but maybe only an intermittent one or an odd "one off".

If you ran a little lumpy briefly and did not see a CEL then probably one of the MAFS had a temporary "out of range" in some place in the RPM range. When the ECU loses input from the MAF(s) intermittently (or permanently) it will revert to a fixed fueling table or use a speed density table backup. These fixed tables tend to be overly rich (for engine preservation). Speed density tables actually work actively, in conjunction with a MAF frequency input to produce a stoichiometric AFR The ECU will return to MAF fueling if the input returns within a given time period and a CEL output will not be given.

Since you have no CEL from your first post, it really leads to an intermittent P0102. So, if it were mine, I'd delete the code, drive it to see if I could recreate the original conditions to see if a P0102 is reset (especially if it resets w/o a CEL). If that is the case, then I would be leaning towards a bad connector at the MAF or a dirty or lazy MAF and NOT a permanent MAF failure, or especially not likely to be an air leak past the MAF.

Just some additional FYI.

 

Mine had similar issue that was resolved by following the driver side maf wires down and locating the splits. You have to peel off all the oem tape and shield crap that is all hard and will flake off practically in your hand. The wires inside were arcing because the heat from turbo and all else in the very tight spot. If you can get the upgraded connector great but if not, with some hockey tape and a little patience you can get your car going again. You have to just go pretty deep down there is all. Mine I actually re-routed wires and tie wrapped away. Once again you have to get deep down as that is where mine was having issues. Since fix I haven't had issues again!

There was also a $40 sensor in front of engine bay that is relatively easy to get to that has gone on me that triggered funny codes. Try the bwings suggestion of upgraded connector or take a look as per my description above. I liked the hockey tape as it sticks better than electrical I find under hood.

 

Removed the air filters and boxes. Removed the MAF`s. Gave everything a thorough, but gentle clean. Wire condition and plugs looked in remarkably good shape.
Re-fitted all components, cleared the codes and so far, so good ! Fingers crossed !!
Thanks for all the advice, its greatly appreciated.

Beo...

 

Mr. Beo - Glad to hear back from you and good news that you appear to be sorted!

Mr. DMaffo - That is good new info and a very good find on your part. Typically what has failed on the MAF connectors is the female side of the connector. The spring connector fatigues over time from many heat cycles causing an intermittent failure in the connect. They were a poor design in the first place as these should last forever. The issue is very hard to diagnose as the connector looks good. Here is a pic of mine from the RS (4 pin). Poor photo but the top spring conn is a slightly larger gap as this is the connect that would fail occasionally.

 

Nearly a week past now, and it has been used everyday, still looking good ! Don't want to tempt fate tho…..

Once the weather warms up a bit, I am going to make a point of investigating all these troublesome bits. Prevention being a wise move.

Thanks again,

Beo………..

 

Good info right here. Does anyone have a source for the updated pigtails or parts number? Like many, I like to do some PMS so she runs better and longer. Gate to be on a road trip and something happens that could have been prevented.

 

This is the one (quantity 2) that I purchased. It replaces the early model ones used in production. They are 5 wire, so, for the RS 4 wire, just clip off the fifth pigtail. Just MAKE SURE you clip the correct wire.