Engine management light and misfire

[vc-10]

Crasher, what would the symptoms of jumping a tooth be? I've got a 12v 1.2 Polo, hope that doesn't happen to me anytime soon!

[Crasher]

It runs like a bag of ****!

It often happens if oil changes have been neglected or unfortunately (for the mechanic doing the job) just after an oil change. I am always extremely cautious with the 3 cylinder engines when doing an oil change, I like to crank them over plugs out (coil packs disconnected from the harness) and get oil pressure up on the starter before running them up.

[swany99]

i have intermitant fault code p0301 as stated, also as said it is electrical not mechanical ie;timing chain as when fault occurs losing earth to power cyl 1 injector and when swapped 1&2 injector plugs lost earth to cyl 2 and cyl 1 was ok, as said suspect ecu just need to know if there common failure on the 1.2 3 cyl engine before buy one?????????

[VAG-tech]

Some engine management systems run a strategy where in the event of a single cylinder misfire being detected fuelling will be shut off to that cylinder to prevent catalyst damage, this could be what you're seeing.

[vdubus]

Have 2005 Polo BKY engine 1.4 petrol runs very bad at low revs almost stalling & doesn't take the boot too kindly, Engine management light on (orange). Has had oil, oil filter, air filter & plugs replaced less than a month ago, would this be coil packs?? Whats the best way to eliminate the bad one?

[Crasher]

The BMD doers have cylinder misfire shut down strategy but swany, first of all I was replying to vc-10’s question and secondly,

16685 (P0301) Cyl 1 Misfire recognised 035 – 001 Sporadic fault

is not an electrical fault. If the misfire moves to another cylinder when parts are swapped, then one of the swapped parts is at fault. If the misfire does not move, then another area is at fault. A common fault on the BMD is exhaust valve failure, injector failure does happen but is not common and ECU failure is almost unheard of. I can’t tell from what you say if the misfire does move or if it is always on number 1

[Crasher]

Have 2005 Polo BKY engine 1.4 petrol runs very bad at low revs almost stalling & doesn't take the boot too kindly, Engine management light on (orange). Has had oil, oil filter, air filter & plugs replaced less than a month ago, would this be coil packs?? Whats the best way to eliminate the bad one?

Yes, as the coil packs have been off, it is likely to be a coil pack, a code rear will tell you which one. It is probable that the other three will fail later so I advise you to replace all four.

[swany99]

i know where you are coming from with mechanical failure on cyl1 but this fault only happens now and again and only at idle and runs fine any other time with no lag which with a dogey exhaust valve you would expect fault to be there all the time and would expect to lose a bit of power if exhaust valve was looking as compression down. Can you tell me if it is the ecu that gives injectors earth on/off and is there anything else in the system that could cause it to stratigically cut-off power to cyl 1 like ie;maf sensor fault?

[Crasher]

The BMD does not have an Air Mass Meter (MAF), it has a “Thrust sensor” which is a combined Inlet Air Temp sender (IAT) and Manifold Absolute Pressure (AMP) sensor.

The injectors have a common power feed on the red/yellow wire, which changes to a blue/white at a 14 pin connector in the engine bay and then goes into another connector on the bulkhead before getting power from a 10 amp fuse at position 25, itself fed by the fuel pump relay. The injectors are earth triggered directly from the ECU with no connections which reduces the possibly of a poor connection being the problem.

The coil packs are earth fed from a common earth on the head and another earth in the harness with a common power from fuse 37, itself powered by the main ECU relay. The coil packs are individually trigged by the ECU with no connectors in the lines.

[swany99]

so what you think about what i said about if exhaust valve or timing were incorrect would be constant fault and power loss? could any other sensors on this engine cause it to shut down number 1 cylinder? as stated before suspect ecu as earth signal drops off to injector 1 wiring and only intermitant can go 1-2weeks without the fault then happen but only ever at low idle then most times go to drive off again and it will stall switch ignition off and back on start up and drive ok like re-booting ecu and it will be fine again.