Misfires at Idle, stock ED30

[Ron, Edition30]

Does anyone know whether occasional misfires at idle are normal or not? I've been logging VCDS misfire counters and am seeing intermittent misfires on cylinders 4, 3 and 1. This predominantly occurs whilst the car is idling (engine both cold and warm) and to a lesser degree see misfire counts intermittently through the rev band as well.

It's never logged any related fault codes and has no dramatic loss of performance. Misfire counts have been up to 20 for periods of a minute or two. I understand from a VW tech that a fault code will trip if the count reaches 100.

VWUK customer care said that it is not normal and should be booked in to be checked under warranty. Just wonder how far I’ll get with the dealers without a fault code present.

Cars an 08 model year and has done 16,000 miles running on Vpower.

I've searched and found conflicting views on misfire issues and dealer responses to them. I'm aware of most of the potential causes and fixes, just would like peoples views on whether some misfires are normal or not.   



Cheers
Ron.

[fuscobal]

It's not normal. As your car has pretty low mileage I suppose it can't be because of carbon deposits on the valves. Check your coils and sparks. A very cold winter like the one we just had this year will accelerate theirfailure. When you start the engine on cold days, do you warm up the plugs first by keeping the key on the first position until all light go off or you instantly start the engine?

[Makaveli]

When you start the engine on cold days, do you warm up the plugs first by keeping the key on the first position until all light go off or you instantly start the engine?

Is it good practice to always do this...

[Ron, Edition30]

Always wait for the lights to go out before engaging the starter.  Misfires occuring at idle even after the engines been running for a couple of hours. 

[NB07]

When you start the engine on cold days, do you warm up the plugs first by keeping the key on the first position until all light go off or you instantly start the engine?

Is it good practice to always do this...

we always do this for my misses diesel but I wasnt aware that was something to do with petrols  

i normally just drive it softly until up to temp as a normal practice for the turbo..

[bowie]

Am I going mad here ?  I have never heard of 'warming plugs' on a petrol engine !   Regarding the misfires, I had similar on my 06 GTI. Plugs were shot.

Chris.

[Rockdrummerzero]

Yes I agree, "warming plugs up" - lol, could you please explain which bit of your engine warms the plugs up on a petrol injected car, the only way you can possibly warm your plugs up is to take them out and put them in the oven...

[FamilyDub]

I do the diesel-style 'wait-two-seconds' before firing the engine.

Cheapest/easiest fix might be to start with sparkies? We have had a crazy winter...

[robdf2]

Hi Guys ,

Poverty kindly showed me this thread so i thought i would tell you my problems and what SEAT thinks of missifres that are logged.
I drive a 2008 Leon Cupra , at 4,000 miles i had a new cylinder head fitted because of missfires ect , and about 2,000 miles later the original problems were still there.
I have put up with this for 18 months and decided i had enough and got in touch with SEAT.
My car went into a dealership for a week and SEAT sent a technician down from their head office to inspect my car.
To them i had reported missfires being logged (i actually gave them a printout from vag com which was done the night before) bad fuel consumption and lack of power.
My car's exhaust also pops and bangs on every gear change and intermittently while driving.
I also had told them that no fault codes were on my car and none have been logged.
My car is standard with no modifications.

Basically verbally they told me everything was in tolerance , a few days later i recieved a letter giving me a breakdown of their findings , i have added some extracts below.

"A member of SEAT technical support carried out investigations with the following results"
"the RMVB (measured value blocks) for the vehicle was monitored whilst on warm up phase. The engine ran smooth and warmed up evenly with no fault codes stored. Misfire recognition did count up to 15 in a 5 minute warm-up but this would best be described as "mis burn" rather than a mis-fire due to aggresive camshaft lift and duration"
"Once up to temperature the actual boost , fuel trim measured air mass and lambada stream were checked with no anomalies detected.The vechicle did not pop on over run however this is a known characteristic of the vehicle due to its high performance turbo characteristics."

"A comparison vehicle was used and it was found that this vehicle also counted numerous missfires on warm up phase and no difference in blocks were monitored while driving"
"Therefore it is our opinion that both the counted misfires and pop through the exhaust under certain conditions are natural attributes to this type of vehicle , and is classed as manufacturing normailty , therefore this is not deemed a fault with the vehicle"

The letter contridicts it self on numerous points , with missfires being used but descibed as overburn ?
I have been to many SEAT meets and no other Cupra standard or mapped has the same problems i have.
One interesting comment was made by a fellow forum member which was his car does nothing like mine so does that mean his car is faulty because it doesnt do it?.

I have a lot of opinions on this matter and have had 18 months of ownership hell and battles with SEAT , i will post some more comments later on but this is by no means over.

Rob.

[Ifti]

When you start the engine on cold days, do you warm up the plugs first by keeping the key on the first position until all light go off or you instantly start the engine?

Is it good practice to always do this...

So we should always do this on a cold morning??
Never heard of 'warming the plugs' by keeping key at first switch before!

Can I just knit some gloves for the plugs?? 

[Ron, Edition30]

Hi Robdf2, Sorry to hear of your troubles. Hope you get to the bottom of it. Your problems seem to be a lot worse than mine.

For me I wouldn't even know there were any issues if it wasn't for VCDS. Car drives well. No shaking, popping, loss of performance and fuel consumption is reasonable (the last 1640 miles 27.1 mpg, 50/50 city driving and spirited country drives).

Misfire counts on cylinder 4 seem to be the worse followed by cylinder 3 then 1. Curiously cylinder 2 has never logged any misfires that I can recall.

Going to book it in to be checked in the next week. The symptoms are reliably present so the techs should be able to detect the misfires in the workshop, which should hopefully aid with the diagnosis and troubleshooting.

Would like to hear from anyone else with VCDS to see if they are having any misfires at idle. I've been monitoring misfire counts whilst leaving it idling for 15 minutes or so. I'm also logging the misfires whilst out on longer drives and the symptoms are consistent (albeit intermittently).

Thanks for the input guys. Will keep you updated.

Cheers
Ron.

[sixpot]

I do believe, the bit about "warming the plugs" on a petrol engined car is a wind up!!

[Ron, Edition30]

Cars booked in at the dealers for diagnostic / warranty repair work next week. Will update with the results.

Cheers
Ron.

[Ron, Edition30]

I’ve just got back from visiting the dealer today. Without a fault code they can do nothing which is a annoying because I'd already told them there were no fault codes present when I phoned and booked the car in. So a wasted journey in that respect.

Seems to be two issues (technical & bureaucratic):

1) Misfires without tripping a fault code being normal or not?

Quoting from my job sheet / invoice from today "Carried out gudied fault finding, no faults found. Spoke to tech, checked smoothness on idle All ok. At times missfire detection can log small misfires but not actual misfires unable to fault" End quote.

I could try swapping the coilpacks myself on cylinders 4 & 2 over and see if the misfires follow the coilpacks. This is something I would have expected the dealer to have done today but without the fault code being present they didn't get to that.

2) Getting VW warranty to pay out for misfire faults that haven't yet tripped a fault code.

If I had offered to pay for the work to be done instead of trying to claim from VW warranty would they have actually been able to stop the misfires occurring?

I still feel that any misfires are not normal, and in my case having only cylinders 1,3 & 4 misfiring would lead me to believe that there is a something unique to those cylinders that is causing the misfires. If there were intermittent misfires on all cylinders then I might then believe that these engines do indeed misfire occasionally.

I've been monitoring this over the past few months, initially only cylinder 4 was misfiring but gradually cylinders 1&3 have begun misfiring as well. So according to the VW dealer today,  cylinders misfiring below the level that would cause a fault code is normal. But cylinders that haven't misfired before which have now begun intermittantly misfiring does not seem normal to me.

I think it time to contact VW UK again...

Anyone have any views?

Cheers
Ron

[cmdrfire]

1) No need to "warm-up" spark plugs for a induced combustion engine (as opposed to a compression engine, where "warming up" glow plugs aids initial combustion).

2) Can't comment authoritatively on the Golf/VW's practices, but generally, it is likely that you are getting false positives (the "overburn" comment mentioned in the Seat technical findings). Tolerances/thresholds for "misfire detection" may vary based on software and hardware revision and therefore some vehicles may be more susceptible to detecting a "misfire" event where none is present.

Detection of misfires increasing over time and in cylinders where they were previously not present may indicate changes in the cylinders/sensors and may not necessarily be indicative of a fault condition.

I would imagine the reason VW has a high threshold for CEL activation (100 "misfires" detected, I recall reading earlier in the thread) is because they are fully aware that the sensor will pick up false positives (in fact you would want it to - better to be more sensitive) and that a real fault condition only exists when there are more than x number of events detected over a certain time. This is normal practice.


@RobDF2, popping/banging and so on does seem indicative of "misfiring" but may not be indicative of a fault condition being present (or: said conditions may be within the fault tolerances of VW/Seat and therefore not classed as a fault).

/not too consoling but hopefully a bit helpful.