Need Help - AMF TDI 75

C

Crash2474

New Member
Hello,

I dont have a A2 but have a Polo 6n2 1.4Tdi AMF, and have been have same problems, specialy the first start of the day or if the car sits when i go to work and get off after 8,9 hours.
The problem is that when o try to start if the glow plug light doesnt go off after +/- 1sec. and it goes out after a few secs. the cranking somes "heavie" or "low batery" when it starts the engine revs by it self to 1800/2000rpm, it doesnt happen every time by when it happens its annoying.
In VCDS the error recorded reports to the coolant sensor.

I already have replaced:
Coolant temperature twice (one with a non original but good make and recently with the original from VW)
Battery (VARTA)
Glow Plugs (Bosch)

Also have replaced that dont have nothing do with it.(i think)
Oil Pump chain and all of the sprockets (OEM)
Timming belt + water pump (INA)
Turbo rebuild
New alternator (Bosch)
Power Steering pump (Bosch)

The car after it starts the idle sits higher then when it doesnt happen.
Can it be the injectors?
Can i check in VCDS?

Any other idea? please
 
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So when the glow plug light stays on for longer than normal before you start, the engine idles at a higher rpm than normal?
 
CrispyEdd said:
So when the glow plug light stays on for longer than normal before you start, the engine idles at a higher rpm than normal?
Click to expand...
Hello CrispyEdd, thanks for helping.
Not allways, yesterday it happened even after the car beeing driven and the temp beeing at 90ºc but the idle was normal and it didnt rev by it self.
 
my money is on the anti shudder vavle being open. throttle control valve , as the pd 150 i had did similar , check the reading before you start the car with vcds ,
 
robskiA2tdi said:
What is the coolant temperature displayed in vcds or any obd phone app after long stay?
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Hi robskiA2tdi, thanks for helping.
With the old sensor i did see negative temperature -30ºC or close to -28ºC.
With the new sensor i changed it 2 days ago, i will check it.
 
will be under throttle body position sensor . i think. they get gummed up from egr dumped rubbish back into the intake ,
 
kraig22 said:
my money is on the anti shudder vavle being open. throttle control valve , as the pd 150 i had did similar , check the reading before you start the car with vcds ,
Click to expand...
Hi Kraig22, thanks for helping.
Do you know what measuring block is it um VCDS?
 
Crash2474 said:
Hi Howey, thanks for helping.
Will do this weekend.
Click to expand...
When you mention the elevated revs - does this manifest itself as the car occasionally spontaneously revving (ie, like a boy racer at the traffic lights) for a second or two immediately after starting up?

Classic sign of the injectors being worn and needing a refurb - result of an unmetered dribble of unburnt fuel being left in the combustion chamber when the engine is switched off. My AMF project car did this every few starts for the first year I had it until I got a set of suitable injectors second hand sent away to Darwen Diesels for a clean and refresh with report; they came back calibrated as a matching set and once fitted made a huge difference to the smooth running and fuel economy of the engine. This won't come up on VCDS because it is due to unmetered dribbling rather than actual instructed metering by the injectors themselves.

Concur with comments of others that the sluggish "low-battery-like" cranking is almost certainly the starter motor earth that needs to be either cleaned up at its contacts or the cable needing to be replaced. Had that problem as well on both diesel and petrol A2s.
 
Robin_Cox said:
When you mention the elevated revs - does this manifest itself as the car occasionally spontaneously revving (ie, like a boy racer at the traffic lights) for a second or two immediately after starting up?

Classic sign of the injectors being worn and needing a refurb - result of an unmetered dribble of unburnt fuel being left in the combustion chamber when the engine is switched off. My AMF project car did this every few starts for the first year I had it until I got a set of suitable injectors second hand sent away to Darwen Diesels for a clean and refresh with report; they came back calibrated as a matching set and once fitted made a huge difference to the smooth running and fuel economy of the engine. This won't come up on VCDS because it is due to unmetered dribbling rather than actual instructed metering by the injectors themselves.

Concur with comments of others that the sluggish "low-battery-like" cranking is almost certainly the starter motor earth that needs to be either cleaned up at its contacts or the cable needing to be replaced. Had that problem as well on both diesel and petrol A2s.
Click to expand...
It only does it immediately after starting up and not everytime, i notice it more when the day is cold (8ºC - 15ºC winter weather) in Summer rarely does it.
 
Hi,

Sorry that i didnt report in so long but only last month changed to coolant sensor (green) G62 for one from VW.
Cleaned the earth cable, changed the cable that goes from the battery to the starter for a thicker cable.

Now a keep getting this fault:
Screenshot 2024-03-25 020159.png


The temperature in ECU and cluster are the same, ive tried to clear the fault but it comes immediately up again.
Any other coolant Temp Sensor? This one is already the 3th one.
 
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Crash2474 said:
Hi,

Sorry that i didnt report in so long but only last month changed to coolant sensor (green) G62 for one from VW.
Cleaned the earth cable, changed the cable that goes from the battery to the starter for a thicker cable.

Now a keep getting this fault:
View attachment 121259

The temperature in ECU and cluster are the same, ive tried to clear the fault but it comes immediately up again.
Any other coolant Temp Sensor? This one is already the 3th one.
Click to expand...
do you have a chance to see voltages with multimeter on sensor plug pins when sensor in and out? it suggests that supply voltage is not there or signal wire dead
 
There is only one G62.

If the sensor has been replaced and is behaving but there are still error codes, the other possibility is that either the connector that the sensor attaches to or the wiring loom leading to the connector have a fault. I had this with the oil pressure switch loom - the insulation of the wire was cracked around 5cm away from the connector. I was able to source a new connector pre-fitted with a length of wire and replace the end of the cable, cover the join with heatshrink and seal it up. If there is an obvious crack in the wire insulation even taping this up cleanly may suffice to fix the fault.

If you do need one, Google / Ebay search for 4B0973712 - suitable wired connectors come up.
 
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Robin_Cox said:
There is only one G62.

If the sensor has been replaced and is behaving but there are still error codes, the other possibility is that either the connector that the sensor attaches to or the wiring loom leading to the connector have a fault. I had this with the oil pressure switch loom - the insulation of the wire was cracked around 5cm away from the connector. I was able to source a new connector pre-fitted with a length of wire and replace the end of the cable, cover the join with heatshrink and seal it up. If there is an obvious crack in the wire insulation even taping this up cleanly may suffice to fix the fault.

If you do need one, Google / Ebay search for 4B0973712 - suitable wired connectors come up.
Click to expand...
I concur with Robin above. The temperature sensor G62 is a thermistor. Basically a vairable resistor with heat. The colder it is the greater resistance of the sensor. So if previously VCDS was reading -30C for G62 as you reported near the start of this thread, that points to increased resistance in the sensor or wiring. Sounds like you had a crack in the wiring which has now snapped and is occasionally making contact.
 
Hello Guys,


Finally, i think i found the problem.
I Started by removing the loom from the sensor(back of motor) to the connector(Front of motor) and found 3 of the 4 wire pinched but not to the point if would fail with the multimeter in continuity but just in case a got a new connector to replace and rewire.

After rewired the new connector, i connected the car with vdcs and cleared the error code and it didnt came back so a moved the loom that goes under the battery and the error code came right back, so i started opening protection of the wires and just before the "T" that goes to the injectors i found 1 wire (white that goes to the sensor) just broke in my hand, soldered and isolated.
I did attach a image just for reference.


No more sensor error and the plug light goes out in a sec or less just perfect. No more hard starting:cool:

Thanks all
 

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  • Screenshot 2024-04-08 192644.png
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Crash2474 said:
Hello Guys,


Finally, i think i found the problem.
I Started by removing the loom from the sensor(back of motor) to the connector(Front of motor) and found 3 of the 4 wire pinched but not to the point if would fail with the multimeter in continuity but just in case a got a new connector to replace and rewire.

After rewired the new connector, i connected the car with vdcs and cleared the error code and it didnt came back so a moved the loom that goes under the battery and the error code came right back, so i started opening protection of the wires and just before the "T" that goes to the injectors i found 1 wire (white that goes to the sensor) just broke in my hand, soldered and isolated.
I did attach a image just for reference.


No more sensor error and the plug light goes out in a sec or less just perfect. No more hard starting:cool:

Thanks all
Click to expand...
That's really positive - congratulations on the repair!

The photo does underline how cramped the underbonnet area of the AMF Polo is compared to the A2 at the front end - I've been working in that exact area in my A2 over the weekend. The presence of the battery over the left side suspension turret means that there is so much more clutter in terms of cables, pipes and so on up in the air just there - I just had to remove the boost pipe and can get straight into a void over the gearbox casing next to the temp coolant sensor with just the ABS and A/C pipework causing a bit of interference.

Obviously, towards the rear of the engine bay in the A2 there is the cabin air intake trumpet that blocks access to things near the bulkhead such as heater matrix-linked coolant pipes, so we have our own troubles (strut top bearings and so on)..
 
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