Random misfire 1.4 Petrol AUA

Bargepower

A2OC Donor
Finally get my EML light out with a new NKG pre-cat lambda and now I have a random misfire.
This started before the lambda was fitted, so it's not that.
When it happens, it's between 1700 and 2200 rpm but only if the car is not under heavy acceleration.
If I give it plenty of right foot, it stops. It is also more pronounced when running uphill.
There are no error messages in VCDS.
It started a week last Wednesday as I was on the M4 in torrential rain - it was more like a canal than a road.
I'm thinking it may be water induced, but being a novice working on an A2, I'm not sure where to start looking :confused:
Any pointers to get me started from the A2 gurus here?

Cheers
Ian
 
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Finally get my EML light out with a new NKG pre-cat lambda and now I have a random misfire.
This started before the lambda was fitted, so it's not that.
When it happens, it's between 1700 and 2200 rpm but only if the car is not under heavy acceleration.
If I give it plenty of right foot, it stops. It is also more pronounced when running uphill.
There are no error messages in VCDS.
It started a week last Wednesday as I was on the M4 in torrential rain - it was more like a canal than a road.
I'm thinking it may be water induced, but being a novice working on an A2, I'm not sure where to start looking :confused:
Any pointers to get me started from the A2 gurus here?

Cheers
Ian

Buy a can of WD40 and spray that liberally all over the plug leads and both ends (Spark plug and coil pack). That should get rid of any moisture (if there is any)

If that makes no difference then it is something potentially more serious.

See if you can somehow try a swap of the coil pack and see if that resolves it (don't just buy one on the off chance that it will fix it, try a swap first)

Changing the spark plugs MIGHT help.

If all of that does nothing there is a possibility that it might be burnt / sticky valves, but that is a last resort (it does often happen, the valve stems on the 1.4 are so thin they look like nails and they can cause problems)

Steve B
 
I'll give that a go with the WD40 in the morning.
I was wondering about the coil pack. I have a money off voucher for a parts supplier (long story involving a Fiat, so we won't go into that) as such I could get a new Bosch one for less than £30, so probably worth changing anyway.
I was recently speaking to the previous owner, they ran the car for 2 years on Asda petrol.
Probably worth bunging some Shell Optimax or Tesco Momentum 99 in the tank?
 
I'll give that a go with the WD40 in the morning.
I was wondering about the coil pack. I have a money off voucher for a parts supplier (long story involving a Fiat, so we won't go into that) as such I could get a new Bosch one for less than £30, so probably worth changing anyway.
I was recently speaking to the previous owner, they ran the car for 2 years on Asda petrol.
Probably worth bunging some Shell Optimax or Tesco Momentum 99 in the tank?

I always recommend using the super fuels like those, just in one tank in four at least.

They do clean the system reasonably well.

You could also try a bottle of injector cleaner on one tank too, once you have pushed a few gallons through take the car for an "Italian tune-up" (a run down the motorway at highish revs just to blast some of the muck out.

Steve B
 
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LOL, I guess not!

That is what happens when like me you have 7 TDIs to look after!

Sorry

Steve B

No problem!
One car is enough to look after in West London.
It's £130 a year just to park on the road outside - and £40 extra if it's a diesel, even though it has lower emissions!
From the 23rd October, to drive an A2 into Central London will cost £11.50 congestion charge and £10 toxicity charge - per day!!!
I've got to nip to Wembley later, so if the Tesco pay at pump has reopened next to Ikea then it can have a tankful of Momentum 99.
 
For my A2 Changing the spark plugs help all the time.
I have spotted that when the spark plugs get over 20 000km the car starts to make random misfire especially from 1500 to 2100 rpm.
New spark plug and everything is fine for another 20 000km
All the time i spotted this the car have NGK spark plugs.
 
also check the plug leads as any AUA engine that I had did not have coil packs, I chased a misfire for some weeks before I found that a plus lead was allowing the spark to go to earth before it got to the plus itself
would start fine from cold then as it warmed up would drop onto 3 cylinders, it is a tiny hole in number 3 plug lead about 1.5" from the bottom of the lead
 
Electrical problems on the HT side tend to manifest themselves more under load and on the LT side they are more consistent, so in this instance I would think more fueling side. Not much help I know, just experience.
 
Well, the latest development has now manifested itself.
Stuck a fill of Momentum 99 in the tank and went for a little blast up the M40 for about 20 miles out, then back.
By the time I was back on local roads heading home, the misfire didn't seem anywhere near as bad.
300 yards from home, rev counter dropped to zero and stayed down, EML light on, ESP light on, airbag light on, red oil warning light on, multiple buzzers blaring.
The engine is still running sweetly at this point!
I pulled over, and switched off.
Gave it about 20 seconds (mostly for me to recover from the shock of that infernal siren of a warning buzzer) then tried a restart.
Fired first time, all warning lights out except EML which I'll investigate with VCDS tomorrow.
A possible crankshaft sensor or camshaft sensor fault?
Hey ho. I'll get this car running perfectly if it kills me.
 
Well, it appears I've fixed the problem.
A quick scan with VCDS this morning gave the following:

1 Fault Found:
16706 - Engine Speed Sensor (G28): No Signal
P0322 - 35-10 - - - Intermittent

So I dived into the nether regions of the engine, and a little investigation found that the plug and socket for the crank sensor had water in them.
I've dried them out with a hairdryer (the domestic management isn't a happy bunny), given them a light squirt of WD40, and wrapped the plug and socket in self-amalgamating tape to waterproof them.
Fingers crossed it's a permanent fix. No misfire, much more lively acceleration and no more rev counter drop outs...
Result!!!
 
Well, it appears I've fixed the problem.
A quick scan with VCDS this morning gave the following:

1 Fault Found:
16706 - Engine Speed Sensor (G28): No Signal
P0322 - 35-10 - - - Intermittent

So I dived into the nether regions of the engine, and a little investigation found that the plug and socket for the crank sensor had water in them.
I've dried them out with a hairdryer (the domestic management isn't a happy bunny), given them a light squirt of WD40, and wrapped the plug and socket in self-amalgamating tape to waterproof them.
Fingers crossed it's a permanent fix. No misfire, much more lively acceleration and no more rev counter drop outs...
Result!!!

Hi
I had just the same problem yesterday... G28 sensor, this is crankshaft sensor, right? From where should I look for the plug? Somewhere on the clutch side, does it show from under the car or up side?

Thanks in advance
 
exactly same problem here, rev counter drops out sometimes... the misfire was easily sorted using just new bosch 4 tip sparks and lucas leads. 1 of the leads had a pin hole in the rubber and must have been releasing the spark against the engine block. running sweetly now, after oil change and bosch filter. Was worried as all the lights do come on with the oil warning also, but if its a g28 sensor, i'll try dry it out :)
 
It was actually water in the plug on my car, not the sensor itself.
I might just get a spare one, though, just in case.
 
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