A3 1.6FSI multiple misfire.

[cgreen1993]

• Good evening all,
  
  I'm usually quite silent online, but need some advice. I own the above vehicle, which has recently developed a misfire. So, far I have done the following:
  
  Checked for fault codes with VCDS; and have the following:
  
  Multiple random misfire
  Cylinder 1 misfire
  Cylinder 2 misfire
  Cylinder 3 misfire
  Cylinder 4 misfire
  
  Cylinder 2 is the main offender, using the misfire counter, this one seems to missing on over rev.
  
  I have done the following.
  
  Replaced coilpacks, spark plugs & fuel filter.
  Cleaned the earths behind the headlamp.
  Compression tested each cylinder (all ok)
  BP Ultimate fuel
  New oil cap (I've read this has some from of effect)
  
  Some perhaps, noteworthy points.
  
  Rev counter is slightly off, reading 400rpm on idle
  
  When setting the readiness, the car runs without fault for approx 10 seconds on the following step.
  
  Basic setting on
  Idle
  Lamba control
  
  When lambda control is 0% the car runs perfect no misfire, as the test starts and the percentage increases the misfire comes back into the vehicle.
  
  Could anyone advised further, there are no fault codes for any of the lambda sensor, on fault codes for misfiring.
  
  Many, many thanks in advance.
  
  

[SammoVWT]

Thats an interesting fault.. its curious, seems like its not getting enough fuel, due to missing as revs increase more suggests to me a leaner mix. Does the engine look rough (lots of vibration)? Could be loads, (e.g. crank position etc)

How's the battery?

Since you have VCDS, I would just check over the sensor readings - check inlet temp, coolant temp - make sure the values are 'realistic' and inline with your cluster display. If you can, see what your injector duty is at at idle. If its quite high, 60%+ while at idle you might be a bit fuel starved.

One of those diagnosis by elimination types with no codes, my favourite!

Assuming your throttle body is clean and all adapted correctly? Air filter clean etc?

Keeping your Airfilter serviced will help keep your MAF alive - just in case. When it gets dirty all the dirt and grease gets pulled through the filter and cakes the AMM, causes the resistance to go up on the hot wires and then it burns out. Doesnt always generate a full fault also.

[Crasher]

It could be a faulty injector, we are starting to see quite a few FSI injectors pack up, just doing 6 on an A6 at the moment. When it is misfiring and you get a fault code for number 2 and the random multiple, try clearing the code with the engine running and see if the misfire goes away as you clear the codes.

[cgreen1993]

Thanks for the reply Sammo.

The engine does shake quite badly, but it's never consistant, some time shakes a little, some times alot worse.

All the temperature readings seem to be in check, only one that worries me slightly is engine load, it's around 40% on idle, but I'm guessings that's slight higher due to being off a pot.

Battery is good, I have a spare one, so I may try that just to rule it out.

Will have a look at the injector duty tonight when I get back, what usually causes fuel starvation? I have replaced the filter to be on the safe side.

Can the throttle body readiness be set individually or can it be adapted seprately?

Now time for an unrelated VCDS question, where are adaptation codes optained from, like wise security?

It also seems like the ignition timing is too far retarded, is there anyway to advance this through VCDS?


Thanks also crasher, I've tried clearing the fault when the engine is running, still misfires and brings the fault back in within a few minutes.

Does the Lambda control have a bearing on misfires? When I'm setting readiness & lambda control is 0% the car runs perfect.