Hot Maf

[bilko0795]

I have just gone to the garage to change the Maf over for a borrowed one. I placed my hand on the metal part of the Maf to hold it steady and burned my finger and thumb enough to leave a scald mark Surely this can't be right the car has been in the garage over night and on trying to start it this morning it was dead so I left it until id change the Maf and then was going to charge the battery.

Any idea's why this could be.

[Error404]

Hotwire is shorted and constantly on? Check the pins for corrosion etc would be my first step. Sounds like this is your random current drain issue.

[BosnianS2]

I know that that our ECU's apply the voltage to "hot wire" after the engine is turned off for some short time in order to burn off any dirt or residue that has been accumulated while air was flowing through. Maybe Ecu is holding the power constantly there for some reason making your MAF hot. You should take wiring diagram and check this.

[bilko0795]

Just checked for any live feed and found the pin that is to the right of the empty one on the plug is perm live. So I take that the ecu is at fault as I have just changed it with one I got from a member on here also would the maf being hot cause running issues as when I changed the ecu for the homfry one the car felt really quick and now it's seemed to have calmed down a bit not as quick would a dodgy maf cause this.

[bilko0795]

Just went and changed the Ecu's back over and the homfry one was really hot to touch . And now my ecu is back on the perm live feed has gone

[UrS4boy]

Holding Relay and its importance/MAF info

I have just gone to the garage to change the Maf over for a borrowed one. I placed my hand on the metal part of the Maf to hold it steady and burned my finger and thumb enough to leave a scald mark Surely this can't be right the car has been in the garage over night and on trying to start it this morning it was dead so I left it until id change the Maf and then was going to charge the battery.
Any idea's why this could be.

Sounds like the Holding Relay in the ECU has failed at least partially. One of its purposes is to supply power to the hot wire after the engine is off in order to burn off crud. But this is only supposed to go on for around 5 seconds. Sounds like the relay got stuck closed, at least on that function. Swapping ECUs swapped out the failed Holding Relay at the same time.

Holding relay info: http://forums.quattroworld.com/s4s6/msgs/102009.phtml

G70 MAF info: http://forums.quattroworld.com/s4s6/msgs/20442.phtml

[UrS4boy]

Just checked for any live feed and found the pin that is to the right of the empty one on the plug is perm live.

Hmm....not sure about your S2 situation but on an AAN, the MAF connector has five wires in positions 1 to 5, with 6 empty. The holding relay burn-off wire is in Pin 4/6 as a green wire with a violet stripe.

MAF info: http://forums.quattroworld.com/s4s6/msgs/20442.phtml

[bilko0795]

Hmm....not sure about your S2 situation but on an AAN, the MAF connector has five wires in positions 1 to 5, with 6 empty. The holding relay burn-off wire is in Pin 4/6 as a green wire with a violet stripe.

MAF info: http://forums.quattroworld.com/s4s6/msgs/20442.phtml

Just had a look at mine and it's pin no 5 blue wire black stripe so basically the same just colour of wire different.

[Rusty]

Sounds like you've found the cause of your issues. PM prj and see if he can have a look at your ECU

[prj]

No interest in having any more broken ECU's at my house, already got a stack of them.

[Rusty]

...or not then...

[UrS4boy]

Just had a look at mine and it's pin no 5 blue wire black stripe so basically the same just colour of wire different.

Can you post up a photo equivalent to mine to show the wiring that you have? Seems strange at this point.

[bilko0795]

Here we go maf 012.jpg

[UrS4boy]

Here we go

Thanks. I am pretty sure the burn-off signal wire is still in No. 4 of your MAF harness connector, i.e. the blue one with the violet stripe.

[UrS4boy]

Thanks. I am pretty sure the burn-off signal wire is still in No. 4 of your MAF harness connector, i.e. the blue one with the violet stripe.

Accessing Paul N's ADU wiring diagrams, the answer is "YES", the blue/violet wire does come from Pin T55/25 in the ECU, i.e., the holding relay power signal to the burn-off function for the hotwire.

The wiring listing for the ADU MAF connector is:

Position 1 = Brown/yellow to (138) ground (probably the intake manifold?)
Position 2 = Black/green from Pin T55/26 in the ADU ECU (looks like this one might be a white/green wire for an ABY)
Position 3 = Black/white from Pin T55/7 in the ADU ECU
Position 4 = Blue/violet from Pin T55/25 (holding relay) in the ADU ECU
Position 5 = Blue/black 12V power wire connected to the injector wire power circuit which is connected to Pin T55/37 in the ADU ECU (actually from the Holding Relay in the ECU)

There should not be power in Position 5 until the ignition is turned on. As with the hot maf (from power going through Position 4 long after the normal 5 seconds of engine off), this is a bad sign that the Holding relay is fubar'd.

RS2 G70 MAF Schematic: