vw scirocco 2.0tsi missfire help

[stuart313]

They sound as bad as a diesel.

[Willy Nilly]

Is that the legendary German reliability we hear so much about?

[bearman68]

Wheatley173 said:

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

Low engine speed, high load, low throttle is what you need for ignition testing. Foot to the floor and mis firing sounds (more) like fuel to me.

Someone else suggested swapping coils and plugs to another cylinder. This is good advice. Cheap and easy to do.
Forgot that this is an FSI engine, so realistically, testing the actual output from the sensor under driving conditions is difficult. Might just be worth plotting the Obd O2 data when driving, just to confirm probably lean misfire. If the OBD O2 sensor does shown lean misfire, worth checking the plugs for carbon fouling. Lean exhaust gas, and soot laden plugs are indicative of ignition misfire.
Assuming there is evidence of fuel issues (or at least lack of evidence of ignition problems), then testing the injector coil in place is a good plan. The ECU is relatively accessible on these - find the injector wires, and look at the No3 injector waveform under load. I'd be willing to guess a dodgy injector / driver under load and heat.

PM me if you fancy.

Cheers

[morgrp]

Wheatley173 said:

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

sounds like a coil if its getting worse as the engine heats up

[R2T2]

I've had a misfire on a T-Jet engined Fiat.

Are the spark plugs screwed down properly?
are they relatively new?
swap the coil pack from a different cylinder, and see if the misfire moves. (note. Check what the firing order is, some are different, and subsequently I was look at C4, rather than C1 with the issue. Italians eh?)

The First thing I would do is replace the sparkies, then look at the coil packs. It'll most likely then be sorted, but if not, then I would start worrying about head work.

[Wheatley173]

So this morning the car drive so much better being that engine is cold from standing over night, but still not right. Driving back to the garage, when driving over a canal bridge at about 30mph in 4th I notice the hesitation again.

I have taken it back and explained the symptoms get much worse as the engine gets hotter.

I have asked them to change all spark plugs as not sure how old they are and also the coil on cylinder 3.

Fingers crossed

The fact the symptoms gets worse when hot makes me feel that it's the coil.

Peoples thoughts on this

[Ian_UK1]

I'm amazed you've taken it back to the same garage after their ehm, great success with things the first time around! The very best thing you could start by doing is to find someone else.

Secondly, what type of diagnostic software is your current 'expert' using - is it just a generic OBD-II reader that's identifying the misfire by a code or is it a package more specific to the car that can drill-down further to pinpoint the cause? VCDS, formerly VAGCom, is the most commonly used. If it's the former, then all the info you'll likely get is a misfire code. If the latter, then the operator hasn't a clue, as the software should pinpoint the cause.

So, what to do? If you're only getting the misfire on one cylinder (the fault code will tell you that) then we've already eliminated anything that could affect all the cylinders - cam timing, cam position actuators/sensors, MAF, Lambda sensors, fuel pressure, fuel pump, fuel filter, air leaks, bad earths etc. If it was any of these, then you'd have misfires logged on ALL cylinders. So that leaves us with items specific to the particular cylinder that's misfiring. In reverse order of severity, these are plug, coil, injector, compression. In the absence of any sense from the garage, you should do the following:

1) Replace all the plugs - this is just sensible and cheap. You can also do a compression test on all cylinders whilst the plugs are out (to eliminate a lack of compression as the culprit). If you do have low compression on number 3, stop here and take the car to a proper, reputable VW specialist for an engine strip-down and rebuild as the problem just got expensive.

2) Assuming the compressions are OK, if plugs make no difference, then as you were advised above, swap the coils around on number 3 and 4 cylinders. If the misfire moves to number 4, then that coil is fooked. VW coils are notorious for being fooked! Replace the coil and enjoy your car.

3) If the misfire is still on 3, then you likely have a faulty injector - not the end of the world, but a pain to remove/refit and they're quite expensive. Off to that reputable VW specialist again, then enjoy the car.

HTH

Edited to add: under item 3) above, if the problem doesn't move when you swap the coils, then it's also potentially the wiring loom to the coil on number 3, but this would be unlikely unless the loom has been disturbed or is visibly damaged.

Edited by Ian_UK1 on Tuesday 30th June 10:07

[Wheatley173]

So I thought I would update on this.

I've picked the car up after having 4 new plugs and 4 new coils fitted and I'm pleased to say all seems well

I've taken it down some country lanes and made sure it got really hot and I'm pleased with the outcome. Drives so much differently.

Thanks for every ones help

[Ste89]

Hi all I have a 2009 1.4 tsi sirocco with have started a miss fire NO SMOKE when I rev out I have orderd new plugs and could but was Just woundering if it could be something els that cat has full service history thanks

[Wheatley173]

Hi,

I started this thread a long time ago. My issue was down to coil pack. Probably worth changing, if no joy from the plugs. Good luck with getting it sorted.

[Ste89]

Thanks yes I am going to change them all and with new plugs but I was just wounding if it did work what els could it be