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gomi_otaku, Technician
Category: UK Car
Satisfied Customers: 3462
Experience:  VW Technician, VW FastTrack, VW Academy, VW Certified
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Ok story but will try to be as informative as possible. I

Customer Question

Ok long story but will try to be as informative as possible. I have my mums 2003 vw polo 1.2, 3 cylinder petrol. She has had it around 2 years and was bought with engine management light on as was told it was o2 sensor and it didnt affect it. It hadnt all this time. last year before mot i reset the light with my very basic obd2 reader, It went out for maybe a day and keeps coming on. so before this mot i scanned it again and 2 codes came up, the o2 sensor on the manafold and the engine coolant temperature sensor. we bought the coolant sensor and refitted that but because the o2 sensor is so expensive we didnt go for it as we have had absolutely no problems with the wee car. so then i done the other bits it needed cv boot and suspension arm (wishbone) and a track rod end. Take the car off the jack and get ready to test drive it. Oh i cleared the fault codes before fitting / refiting the parts. I also had the battery earth disconected for some time. I got in started it up as normal and we noticed it was smokey (white petrol smelling) it was ticking over then just died. I tried to restart it but no luck, very odd. That was a couple of days ago and i am working on the road outside my house. We have tried the obd2 and showing no faults. Got new spark plugs and put them in. plugs wher slightly sooty and wet. testing after few cranks new plugs where also wet. we have checked and it is getting good spark to all 3 plugs. checked compression and no 1 and 2 where 180 psi and 3 was around 170 so decent compression. my neighbor thinks the injectors are giving too much fuel but the do seem to be squirting and stopping in a rythem, what we have noticed it if we pull the injectors and fuel rail off it will start breifly and cut out as obviously not getting fuel, also if we take the fuel pump fuse out it will also try to start, every time plugs are checked they are wet. fuel pump is buzzing as i think it should when the ignition is turned on and we know it getting fuel just too much. we have also tried starting in flood mode with gas pedal pressed. No i was wondering if i had erased the memory from the computer and the throttle body wasnt working right but it seems to be opening and closing fine, i havent removed it to clean it yet, also heard the egr valve could get clogged i was intending taking this off along with the throttle body and intake manafold to check and clean them but in the car everything looks fine and getting power but could these lead to wet plugs and not starting all of a sudden. have also heard these 3 cylinders can jump the chain easily or burn the exhaust valves but compression ok ? so also thinking timing but there is no easy way to check it seems the pullys and all have to come off and sump to check timing and could the timing cause the wet plugs ? I am baffeled and so is my neighbour who is a mechanic.
Submitted: 1 year ago.
Category: UK Car
Expert:  gomi_otaku replied 1 year ago.

Since you had the battery disconnected for a long time, it is possible that the ECM has forgotten the throttle settings. I would first make sure the faults are cleared, and then turn the key on, off, then on again (engine not running) and depress the gas pedal all the way to the floor and hold it there for about a minute, turn the key off while still holding the pedal down. This should adapt the throttle range in the ECM.

I was thinking maybe the crank speed sensor was going bad, as that often will not set a fault- but you normally would not get spark either, which you say you have.

You should be able to get it started by holding the pedal to the floor, as that kickdown position will cut off the fuel and open it up to more air to purge out the fuel flooding.

Customer: replied 1 year ago.

No just tried it twice there and no change, i did try something similar, the flood mode i mentioned but that was just holding the pedal down before turning the key but the on off on didnt happen either, im still thinking timing, fuel pressure regulator or throttle body etc clean,

Expert:  gomi_otaku replied 1 year ago.

I don't think the throttle body is going to change it, if it doesn't start with the pedal down. Timing you would have to be able to lock the cams in place, though you can at least figure out where TDC is by inserting a long dowel into the spark plug hole and turn the crank slowly until it rises to it's highest point. Make sure you do not turn the crank backwards, only clockwise.

Customer: replied 1 year ago.

Thanks I was leaving that to last, do i just check the timing via the two caps i take off at the cam or do i need to strip the covers and pully wheels etc of at the other side and check them timing marks. Thanks Also if timing was off would not get poor compression

Expert:  gomi_otaku replied 1 year ago.

You should be able to set it up at TDC, like I said, just by inserting a wooden rod into the cylinder through the spark plug hole and turning the engine slowly until the rod is at it's highest point. If the cams don't line up correctly at that point, turn the crank one more turn (the cam turns once for every TWO turns of the crank)