vw scirocco 2.0tsi missfire help

[Wheatley173]

Hi,

I have recently purchased a scirocco 2.0 tsi with and have recently found the car to be having issues with misfiring. This is really noticable when accelerating under load.

I have dropped it off at a German car specialist who I have used several times for my other cars to diagnose. I was expecting something like coil issues or similar.

The diagnostic has shown misfire on cylinder 3 and also maf sensor. I believed the code from the Maff sensor would be due to my friend who has a mechanics head on him pulled the connector to see if it made any difference, which it did not
They has ran over an hours diagnostic and the mechanic who has checked all areas has recommended using a fuel cleaner to help the issue and then to monitor.

This seems like a bit of an easy fix to me and my friend also agrees it seems a bit simple.

I would be totally overt he moon if this simple issue resolved this, but I just have a gut feeling it will not. I was expecting at least coil changes, plugs and maff sensors, so to be told a bottle of fuel cleaner could be the answer seems a bit nice. If the fuel cleaner doesn't solve it, it's going to be removing the head for further investigation.

Can some one prove me wrong, would love to hear from any one whose had a similar experience to me on this and has actually seen fuel cleaner work. I've always had my doubts about it, but then again I've never used it.

Any one with knowledge on the 2.0 tsi with thoughts on symptoms like this.

Thanks

[Al U]

Service history show when the spark plugs were last changed? Could be that or coil pack on the offending cylinder. I would at least do the spark plugs before taking the head off.

[catman]

You're jumping straight to taking the head off? That's a big step. I'd be checking basics like plugs, coils, leads first.

If the car has individual coils, you could swap them around to see whether the misfire goes to another cylinder.

Tim

[SuperchargedVR6]

A persistent misfire on the same cylinder on these DI engines is usually down to a coil or injector. The former is 10 mins work, the latter a good few hours.

[Wheatley173]

No, I didn't intend to jump to removing the head, what I mean is that I already expect that the diagnostic that has been happening today has already checked coil, plugs and Matt

This is why I am surprised to see he only recommend the fuel cleaner . I was certain he was going to say one of the above and can only imagine the head removal if the fuel cleaner doesn't work as all other checked.

[lostkiwi]

Turbo Saabs with misfires are almost always cured with coil packs and/or plugs. Definitely change plugs first and go from there. Plugs often fail under load as the first indication of an issue as the mixture is harder to ignite.

[Wheatley173]

I was starting to think injector if all other areas had been covered off as being ok. I woukd imagine that he feels the injector is dirty and would require being cleaner through the additive, but I would second guess then if that doesn't work it would be replacement.

Any ideas of cost to replace an injector ?

[SuperchargedVR6]

Wheatley173 said:

I was starting to think injector if all other areas had been covered off as being ok. I woukd imagine that he feels the injector is dirty and would require being cleaner through the additive, but I would second guess then if that doesn't work it would be replacement.

Any ideas of cost to replace an injector ?

You could try a Terraclean treatment (they come to you) but I wouldn't hold out much hope of it being a permanent cure.

Mine had a misfire on cylinder 3 also and it was definitely a failing injector. I had all 4 done as it requires removal of the intake manifold, so whilst it was apart and all that. Injectors are about £100 each + 3 - 4 hours labour for a pro.

[SuperVM]

Most likely a coil pack or spark plug, as others have suggested. The easiest way to prove this is to move the coil pack to a different cylinder and see if the misfire moves, by logging misfires in vagcom. If it doesn't move, then try again by replacing the plug. If the misfire is still persistent in the same cylinder, then I'd suggest a fuel injector is the problem. Vacuum and boost leaks can also cause misfiring, though I doubt this would be isolated to a single cylinder.

[Wheatley173]

Well it's apparently ready for me to collect, so we will see how it goes. But I doubt it will last. Maybe I shouldn't be so negative.

Doesn't sound like it can be anything else other then injector if all others have been checked, so at least I have an idea of where I will be standing if it happens again

When I pick it up I'll find out what has actually been checked over as I would imagine plugs, coil and maff had been checked in order for them to come to the conclusion that none of these need replacing

[datum77]

If any car has a periodic misfire, it is 99% certain that it is NOTHING to do with the head/valves/pistons etc. Any fault in this area will be permanent and not just on Thursday's if Eastenders is on. (Damage to pistons or valves cannot mend themselves).
Your problem sounds electrical, and slightly less likely, fuel. This includes the injectors. Renewing components is a method of last resort, but can cure the fault, even if the diagnostic equipment fails to point to anything in particular. After all, that expensive computer equipment is only as good as the guy that's using it.

Keep well away from Kwok Fut.

[Wheatley173]

datum77 said:

If any car has a periodic misfire, it is 99% certain that it is NOTHING to do with the head/valves/pistons etc. Any fault in this area will be permanent and not just on Thursday's if Eastenders is on. (Damage to pistons or valves cannot mend themselves).
Your problem sounds electrical, and slightly less likely, fuel. This includes the injectors. Renewing components is a method of last resort, but can cure the fault, even if the diagnostic equipment fails to point to anything in particular. After all, that expensive computer equipment is only as good as the guy that's using it.

Keep well away from Kwok Fut.

I've just picked it up. There is definitely an improvement, but I'm certain it's not 100% right. Which lead to believe that surely they have had to mess about with coil and spark plug for number 3 and putting it back together has some how improved it some what, but not cured it. I'm starting to think it would be worth replacing the coil and plug in number 3 just see what difference it would make

So based on what your saying you think something electrical being plug, coil or injector then ?

[Wheatley173]

So I've been out for a longer drive and the probkem is still very much there.

I'm sure it gets worse as the engine gets hotter.

My mate seems to think it is the coil if it's heat sensitive

Any one have any thoughts ?

[icepop]

Sounds definitely like a coil pack, someone I know had exactly the same in a Z3, and golf mk 4. Easy peasy to do.

If it proves not to be and it's getting a bit frustrating to find, then 3 series owner had misfire that took a while to pin down to camshaft sensor.

[Faxo]

If it's cylinder 3, swap coils 3 & 4 round. If its still cyl 3, swap plugs round. If it's still cyl 3, either replace injector, or swap injectors round. If it's still cyl 3, you've a wiring or compression problem!

I've done injectors on these engines, they dribble. A few have dribble so much, they've slightly bent a rod. Didn't know until started burning oil, when head was removed you could see a blue line down the bore due to heat

[Wheatley173]

Faxo said:

If it's cylinder 3, swap coils 3 & 4 round. If its still cyl 3, swap plugs round. If it's still cyl 3, either replace injector, or swap injectors round. If it's still cyl 3, you've a wiring or compression problem!

I've done injectors on these engines, they dribble. A few have dribble so much, they've slightly bent a rod. Didn't know until started burning oil, when head was removed you could see a blue line down the bore due to heat

Thanks for the advice, you sound knowledgable on this engine. Do you think though the fact that the symptoms get worse as the engine gets warmer points to a dodgy coil?

I feel like taking the car back tomorrow morning and insisting they fit a new coil to try it

[bearman68]

It's not an ignition problem.

Look at the evidence people.....

Car is misfiring on acceleration. Spark event occurs approx what 35 degree below TDC, on a rich, and low compression cycle.
This is the easiest point at which the coil needs to fire a spark. So if this is the only time it misfires, it aint that. To test ignition systems, drive up a hill, in high gear, and low throttle / engine speed. If there's anything wrong with the ignition, that will induce misfire better than most things.

Let's do the basics - measure compression first (nothing wrong with that), then look at the O2 sensor during misfire events, and then consider the evidence. If it's a lean misfire, it's likely to be an injector.

[Gavin0478]

I know in the tfsi s3 engines there was problems with the fuel pump riser wearing or similar causing misfires.
I have no idea if this is an area worth looking at?

[Wheatley173]

The car is much worse under load say for instance, low rpm in 5th gear, foot to the floor and then it struggles. If I drop it to 3rd it feels much happier although the signs are still there.

So as you say driving up a hill in a hoggish gear, the car would really struggle on this

[Wheatley173]

Also I would say the misfire is always present. Not really noticeable when cold but once heated up its definitely more noticeable even at idle