Engine management light and misfire

[swany99]

Hi all,

i checked a vw polo 1.2 3cyl 2005, has been an on going fault of engine management light coming on when idling and engine misfiring. eventually i was there when fault occured which was mis-firing, did not have my scan tool to check codes so checked old fashioned way pulled the plug to coil packs to and only cyl 1 coil never make noticible engine note difference, so suspect mis-fire on number one so swapped coil packs one and two and fault still stayed at one so coil pack ok, number one was sparking between coil pack and top of plug so wiring ok to number one. when dis-connected number 1 injector made no difference to engine note. I suspect either;

1; Spark plug - not checked yet but due to being intermitant fault doubt this is the fault
2; injector 1 as all feeds to all injector are the same line.
3; cyl 1 deviation or low compression

any one got any ideas or experience of this fault on this engine or anything else that think could cause this.

[kenney]

you are on the right track,can you swap the injectors

[swany99]

i will have you any idea how these are removed. looks like x2 allen bolts and a clip on each injector to release fuel rail is it just a matter of pulling injector out after that or something else hold them in?

also has anyone got a resistance of injector as it will just be a solenoid type injector and all solenoids usually have a ohms resistance?

[kenney]

It is as you have stated remove the fuel rail 2 screws and the clip to each injector,there is no given resistance for the injectors,you can measure the resistance on the other ones,the correct method to check the injectors is to measure the amount of fuel they deliver

[swany99]

ok thanx for info mate will try it and report back on thread what find.

[swany99]

checked polo today engine management light came on checked codes with reader which was p0301-mis detected on cyl 1 and p0351 - ignition coil a
primary/secondary circuit malfunction. First of all i changed the spark plugs which took away error p0351 but mis-fire on cyl1 still present. checked feed going to
injector which was ok, also checked with magnetic field detector which lights up when one detected. 2 and 3 were ok but nothing at inj 1 so swapped injectors 1 and
2 and run fault still on cyl 1 so next swapped wiring plugs with 1 and 2 when error came back checked with magnetic field detector which one and 3 were ok number 2
was down so it tells me its the wiring so metered cables out which was 13.7ohms which is within spec according to auto data. as all 3 injectors share the same feed
and checked feed which was ok i can assume this ok, i assume the ecm gives each individual injector its earth can anyone confirm this?

has anyone had any fault like this and are the ecms common problem?

is there anything else that could cause this?

any info back would be appriciated

also forgot to mention it only seems to be at fault when idle ie; when just sitting at house and traffic lights etc.

[swany99]

anyone?

[Crasher]

So you still have P0301? What is your engine type code?

[swany99]

yes and engine code; bmd

engine will run ok then when sit idle engine management light will come on and it will be code p0301 and as said before its the wiring and as all 3 cylinders have same feed the ecu must give switched earth.i suspect myself its the ecu but not wanting to change just incase thats why asking if any other ones with same fault.

[Crasher]

If you have no injector or coil fault codes the first thing I would do is a compression test and I would also be thinking about pegging the engine for a valve timing check as these engine have a nasty habit of jumping a tooth on the cam timing although not as much as on the 12v. Wiring would be a possibility but it is unlikely, a faulty ECU would be right at the bottom of my list, next to meteor impact. Pulling coils on a running engine can kill a coil instantly. Loss of compression is top of my list, either from a burnt valve or skipped cam timing, most likely a burnt valve, compression test first in my opinion.

[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.

[Crasher]

Yes, jumped cam timing would be a constant fault and a failing exhaust valve would be more constant than what you describe. If you are 100% sure that the earth signal to the injector is intermittently failing it can only be the wiring or the ECU but I would still be extremely surprised if it was the ECU.

[swany99]

well first i'll meter out the earth/signal wire back to ecu and do wiggle test if ok i think i have to try a ecu. i'll let you know how i get on crasher and thanx for input.

[Mariusgti]

well first i'll meter out the earth/signal wire back to ecu and do wiggle test if ok i think i have to try a ecu. i'll let you know how i get on crasher and thanx for input.
Hi, did a new ecm module solved this problem? I have just the same problem on my vw polo 1.2l 2005.

[batteryman]

I had a poor idle but no engine management light on a 1.4Fsi. The car's part throttle performance was terrible at the low end but great when given the boot. It turned out to be a dirty throttle valve - I used throttle valve cleaner spray and a toothbrush together with lots of tissue, taking care that only liquid went into the engine's inlet tract. I fired up the engine and revved it for a while and the fault cleared. I had an engine warning light (emissions) due to the cleaner having gone through the engine and burnt but it cleared after 3-4 startups.

[stevem365]

Hello. Forgive me if this is resurrecting this post but wanted to make sure before I buy the parts and start removing the head on my missus VW Fox.

The car is a 3 cylinder 6V engine code BMD.

Is running terribly and barely makes it to the end of the road and back. Loss of power and showing missfire on cylinder 1 when scanned with VCDS.

I have replaced spark plugs and coil packs and fault remains. After reading lots of posts on here and other forums it would seem it has the common exhaust valve failure.

I purchased a compression tester to check cylinders and got 14 psi on cylinders 1 and 2, and 10 psi (slower build) on cylinder 3.

Do the above readings indicate worn exhaust valves/guides, as I thought it would be lower? or should I be checking something else before breaking out the socket set (and all the other tools required...)

Thanks Steve

[Crasher]

The figures should be 10>14 Bar so 150PSI and above so do you mean Bar instead of PSI?

[stevem365]

Yes Crasher I do mean Bar, doh!! Thanks for the reply - it was you I was hoping would see this...

[Crasher]

Yes you certainly have a compression problem on 3 which is hopefully the exhaust valve as there is nothing that can be done with bottom end. You will need new exhaust valves and guides but the inlets should be fine. I would use Febi parts.

[stevem365]

Thank you Crasher. Help much appreciated. Will get ordering the valves, guides and seals...

[Crasher]

And timing chain kit, gasket kit, head bolts, sump sealant, oil filter, cam fingers and hydraulic lifters.

[stevem365]

I know you are right, but was planning to do the exhaust valves, guides x 6, valve seals x6, headset, head bolts and re-use the timing chain as am on seriously tight budget!!
Car has done about 77K...

[Crasher]

So you won't be upset if the hydraulic compensation elements pump up and smack a valve into a piston or the chain jumps a tooth or three and does the same? I do the full Febi kit for £119 or the basic kit for £80 if the gears are not worn, a set of Febi lifters is £40.55 and a set of fingers £56.21.

[stevem365]

Well that would be slightly annoying :-)
What do you think about the reconditioned head services on fleabay for £225?

[Crasher]

I would rather use a local engineer. When we do them we try and get people to have a VAG exchange head but this gets more difficult to justify as the car ages. Three valves, three guides and a skim would be about £150 at most engineers, that is all there is to a recon head, the rest is dressing.

[stevem365]

Crasher, thank you for your help and advice on this...

[Seifer]

Hello everyone, especially Crasher who is always helping out :)

Yesterday I encountered a similar (if not the same) problem discussed here.
I have a 2007 VW polo 1.4 TDI Bluemotion with around 130.000km
Yesterday I had a main belt change (complete kit) and an oil change.

5 minutes after I drove out of the mechanic garage I noticed the glow plug/engine management light flashing (blinking) and a reduced power to the engine. The engine did not stutter, it just did not accelerate as it did before.
31792
I called up the mechanic who did the work and he said that I should try turning off the car and then back on. After I did it, the glow plug/engine management light stopped flashing. However today, while driving to work it started again.

I read from one of Crashers posts:
"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."

So any thoughts? What should I do? I intend to drive my car to the mechanic this afternoon but I'd love some insight to what might be wrong.
I also read that coilpacks could be the source of the problem...

[Crasher]

This thread and your quote of my post are not relevant to a TDI. Your car will have a BMS code engine and the symptom you describe sounds like a boost control error so it is possible he has left off or incorrectly connected a boost control vacuum hose. The sensible first step would be to have a fault code read done as this will help pinpoint the reason for the "limp mode" it is going into.