The Dreaded Maf?

[Guest andeee]

I originally posted this in the Introduction Section but was advised that it may fit better here.

I'm on my 20th Ford and 3rd Galaxy. Progressed? from a '96 2.0 Ghia Auto through a '98 2.3 Ghia X to a late '00 1.9TDi Ghia Auto with 30K on the clock. I dont do many miles but do tow a caravan to Spain every summer so was interested to read the technical stuff about failing MAF sensors especially from those members who only suffered problems when towing. I set off on the annual pilgrimage to the Med and all went well until I hit stop start traffic on the M25. After a few miles of this I suddenly noticed a distinct lack of grunt and could only get upto about 35 on the flat. Got to the services at Maidstone and called the RAC. Two hours and and a blank diagnostic session later I decided to hole up for the night with a mate of mine who lives close to the M26. Said mate is in the trade and a few phone calls later his contacts came up with the MAF sensor theory, I had been thinking along the lines of overheating Auto box slipping. On the restart everything was OK so decided to take a sensor with me just in case the problem recurred. Tracked one down to Haynes Bros. in Maidstone for the princely sum of

[Masked Marauder]

Typically a MAF has two main components, a thermistor which measures the air temperature and a "hot wire" which works by current flowing through it causing it to heat up. The hotter it gets, the less voltage that it draws to heat up.

 

The hot wire voltage is sent to the EEC processor as a reading between 0 and 5 volts, depending on how much the wire is cooled by the air flow over it. So

by knowing the voltage and the radius of the MAF sensor the ECU can be programed to calculate the physical volume of air flowing through the sensor. And by knowing the volume of air, throttle position etc, the ECU controls the fuel input to the cylinders.

 

But how does this explain the problem? Well contamination of the hot-wire has always been a problem of this type of MAF with some cars worse than others. But if the problem cured it's self, is contamination the cause?

 

So perhaps your diagnosis is correct. The air getting hot in the engine bay being sucked in through the induction piping could be causing the sensor to read over the maximum threshold, that could make it trip out, putting the ECU into limp-home mode. Or perhaps it is just the design of the engine bay makes the MAF overheat. May be the inter-cooler is heating up from the radiator, actually heating the air to a point that the ECU can not believe the MAF so ignores it.

[Guest MATT]

Hi,

 

About your auto box problem, as someone has suggested try to get a oil cooler fitted, we had a ford Granada in the past and we had a similar problem, and eventually the box burnt out and needed replacing, but with an oil cooler. Now we have a ford galaxy 1.9tdi Auto, and there

[Guest andeee]

Thanks to The Masked Marauder and Matt for your replies. Certainly provides food for thought. In one way it is a pity I dont have to tow the 'van more often so as to replicate the situation when the problem occured but on the other hand I dont really want to run the risk of further frustration. The caravan was checked for suitability against my mothers 2.0 TDCi Mondeo so I would of thought the Galaxy should be able to cope with it. Kenlowe are adamant that you cant fit auto box oil coolers to any VW/Audi but I dont know if there are any other systems available.

I'll bear in mind the use of the Tiptronic box for starting off, especially useful in start-stop traffic which was when my problems occurred.