Quantity Adjuster problem

2003 Mk4 AHF. Something odd is going on with the QA. (car is 300 miles away so working on it as I go back and forth)
Problem started with the engine cutting out after a few seconds when starting. Initially I thought it was an immo problem (no spare key to test with) so I deleted the immo. Tested the deleted immo ecu by running it in another AHF and all was fine there. But the cut out after a few seconds persisted in the problem AHF. I then stripped and cleaned the QA including cutting and soldering the joints that have to be cut to open up all the way. No difference. I've brought the suspect QA home and fitted it to my AHF Wagon and it runs but the timing goes full advance and while it does idle it cannot be driven safely. Reverting to the other QA and the problem goes away so this points to a faulty QA. In a day or two I'll head back to the stranded AHF taking my wagon QA to fit and test. (Might take the whole IP just in case)

Both QA coils ohm out with the same readings . Both respond in the same way when the ignition is cycled on and off and both are easy to adjust to set the voltage (.680 volts) when setting up for a first start. IQ cannot be set on the problem car as the motor doesn't run for long enough but its set to the scribed marks made before dismantling.

Faults:
G149 modulating piston (timing) Electrical malfunction-intermittent.
QA N146 Lower limit reached.

The faults follow the faulty QA from vehicle to vehicle. I'm curious as to how the QA alters or affects the timing as there seems to be no direct connection. In other words how does the faulty QA cause the idle SOI to go to full advance? (35 degrees BTDC)

2003 Mk4 (AHF) ???


Bajan

red16vdub said:

2003 Mk4 (AHF) ???
Bajan

Click to expand...

ALH is 90 HP
AHF is 110 HP

The ecm see's the fault and adjusts itself in order to run.

The QA doesn't say anything to the ecu except where it's at, the ecm responds by advancing timing as much as it can.

I might have found the problem. The coil that drives the QA ohmed out okay but failed a megger test to earth. Just need to double check if it should be isolated from earth.

Turns out there was a short in the QA servo windings which only showed up using the megger. Fixed with a spare unit but I'll be rewinding the sevo unit shortly. No fault codes other than QA upper / lower limit reached. Motor behaved as if it had an immo problem.

Refresh my memory; a megger checks resistance with a couple hundred Volts, no?

You said you check the coil resistance in your first post but did you check for a short to ground with the Ohm meter? I know they are only a few Volts but the QA operates at less than 12.

KLXD said:

Refresh my memory; a megger checks resistance with a couple hundred Volts, no?

You said you check the coil resistance in your first post but did you check for a short to ground with the Ohm meter? I know they are only a few Volts but the QA operates at less than 12.

Click to expand...

No short to ground showed up testing with an ohm meter. Only the megger showed the insulation had failed at some point. The megger tests the insulation covering the wire by inserting around 200 volts.

I rewound the QA servo coil. It's 209 turns of .8mm wire. It's a simple job and can be done by hand (I used a 4 jaw chuck in a lathe) I've not fitted it to a running motor yet but will report back when I do.

Mako said:

I rewound the QA servo coil. It's 209 turns of .8mm wire. It's a simple job and can be done by hand (I used a 4 jaw chuck in a lathe) I've not fitted it to a running motor yet but will report back when I do.

Click to expand...

Nice, I have a buddy that loves to wrap coils.
They don't take as much effort if you do it like you did and use a low speed machine to turn it.

Sent from my Armor_2 using Tapatalk

Quite the find, quite the repair!
Must feel good to repair a $900 part for 99 cents.