I've tried to post in ask a tech but for some reason cannot do it, but in despair looking for any last clue to what's left to cause a misfire.

So far I've replaced.....

All four coil packs

All spark plugs

MAF

N75

FPR

Both Lambda sensors

New DV

It's had injector cleaner

Runs on 99 octane

It hesitates and splutters then runs fine at around 2,300 to 2,700 rpm but I'm totally out of ideas......

Thanks

Check breather pipes on side of engine and where they run under manifold

Check breather pipes on side of engine and where they run under manifold...

...carefully and thoroughly. There's a good chance one of them's cracked underneath where a quick visual inspection won't see it.

What engine is it?

1.8t? Could be the coil pack wiring loom, it perishes with heat around the rocker cover

Have you cleaned the throttle body too? Theres a 'how to' about somewhere.

And have you had the car scanned to check if any faults codes have been logged?

Woah that's a huge amount of responses, thanks!

In answer to the questions, it's a 1.8t AUQ,

It's had the full SAI, EVAP and N249 delete, all the breathers have been replaced with new silicone piping, there are no registered fault codes when scanned - which is the confusing part! I haven't yet cleaned out the throttle body so I guess that's one worth trying. But as everything has been replaced at some point and has been running fine it just confuses me as to how it can all of a sudden develop the misfire. I've also tried swapping the coil packs round individually with a spare one to rule out the fact that one might be faulty but this doesn't resolve the issue.

I just can't work the thing out.

So if anybody has the link to the throttle body cleaning thread I'd be grateful, also, I'm sure you'll all know what I mean, but there is a guy with a red skoda octavia who has his own website with guides to everything, I believe he is a member on here but for the life of me I cannot remember the website.

Thanks

Nick

First though, coilpack wiring.

Have you run Vagcom/VCDS to determine which plug or plus are missing? Then move around to see it the misfire moves? If it is constantly the same cylinder then my first thought on mine was compression (expensive) but mine turned out to be coilpack wiring. Stripped the loom back to the side of the block and wound each strand with electrical tape and problem solved(well that particular one) as the spark ends up going to the rocker cover instead of the coilpack. I had lots of issue with misfires due to spark plug and gap size as well due to running remap and LPG. Changed to bkr7e plugs and gapped down to 0.028 with the standard coils.

As you seem to have done everything else then coilpack wiring looks like a very possible cause.

Coil pack loom !!

There multi point injection with seperate injector and infact coils for each cylinder so engine managment can pickup which cylinder is missing and how many times it has done it with a counter,

They do have a sort of egr of sorts but it only works when cold and works the other way so it blasts fresh air down exhaust system to help warm cat up faster or as its commonly known SAI system

What plugs has it got in OP as i've come across penty of cars in past with wrong ones in that ran like a sack of poo

I'll move the SAI bits into this thread http://www.briskoda.net/forums/topic/280011-removing-secondary-air-pump/#entry3318442

More relevant in there

Throttle body cleaning guide - http://www.briskoda.net/forums/topic/129943-cleaning-throttle-body-18t-engine/

The guy with the red Octavia Estate is Rob & his website is - http://www.pimpmyskoda.co.uk

Ah that's brilliant, that's the website I was looking for! As for the plugs they are the Bosch super 4's, I've abandoned the car at home this week as I'm away in Wales. Unfortunately I don't have Vagcom (so if there are any helpful members in the Oxfordshire area (wink wink) then I'd be happy to come and visit you, but, I do have the basic hand held scanner which has never failed me before but it literally doesn't register any codes for this, where as before it would give me an individual cylinder for coilpack failure etc, it even gave me a code a while back for bad earth on cylinder 3 which turned out to be a faulty coilpack. So I will update next week!

junk the super 4s, get some ngk pfr6q.

super 4s have been known to cause problems

Super fours are carp! Cause more misfire issues than the worth of it, bkr7e are cheap copper core plugs that you can afford to replace every oil change or the platinum ones as mentioned above. If its mapped etc then the bkr7e work well

It is mapped yes, in fact it's pretty much rammed out with bits and pieces, I'll create a thread for it in the octavia section, in simple terms its now a K04-001, FMIC, fully siliconed and deleted everything, full custom exhaust system from turbo back, and apart from the block itself I've pretty much replaced everything I can get my tools onto, it's just this misfire that's completely confused me....... :S

Sent from my iPad using Tapatalk HD

Best of luck finding out whats wrong it .... you'll need it

Definitely worth ditching he super 4's for BKR7E's. I had a set of super 4's when the car was converted to LPG as they were recommended by the LPG installer. They an ok but once it was mapped I started having issues, tried a brand new set and it got worst. Swapped to the bkr7e as they are a cooler plug which the LPG prefers and then found this on the "vw vortex" site.

Spark Plugs

OE Plugs: NGK PFR6Q - .032" gap

For Stock Cars - .032" gap:

NGK BKR6E/6962

Autolite 3923

Denso Iridium IK20

For Chiped Cars - .028" gap:

NGK BKR7E/4644 (formerly 6097)

Autolite 3922

Denso Iridium IK22

>Tightening torque 30Nm (22 ft-lb)

>Tightening torque for Coil Packs 7ft lbs

I have also been through all the various coil pack problems as well, upgraded to the hitachi bolt down type which improved things a lot but now running the mk6 2.0T coil packs which allow the gap to be increased as well with the bkr7e.

Ok cool thanks for that, I'll order myself a set and see how I get on, it's been over fuelling for a while now, even though its super economic for some reason it's clearly not at it's best at the moment! I'll start with the plugs and the coilpack wiring loom and give the throttle body a clean and see how it goes!

Do you have Vagcom/VCDS? If not make sure you keep the plug connected when you do the TB clean. Try the plugs gapped at .030 first and if you still get misfires drop them down to .028

Best of luck finding out whats wrong it .... you'll need it

The voice of experience

Few things to check.

Make sure your coil pack wiring is intact.

I had broken insulation before and wire was shorting to ground. This caused a misfire and a coil pack code. The insulation gets brittle due to getting very hot. I re insulated wires and all was fine. Also fitted Audi TT heat shield over wires.

So don't rule that out.

Also did you have misfire before map. If not this could steer towards map. Again I had an aggressive map once and it was failing mot because between 2300 and 3000 rpm was over fueling. It also had a flat spot and spluttered in this range.

Other than that also I sprayed electrical silicon spray on all my sensors and coil pack plugs to get best connection. Simple things but make a difference.

Good luck sorting it.

Sent from my Samsung S3

Few things to check.

Make sure your coil pack wiring is intact.

I had broken insulation before and wire was shorting to ground. This caused a misfire and a coil pack code. The insulation gets brittle due to getting very hot. I re insulated wires and all was fine. Also fitted Audi TT heat shield over wires.

So don't rule that out.

Also did you have misfire before map. If not this could steer towards map. Again I had an aggressive map once and it was failing mot because between 2300 and 3000 rpm was over fueling. It also had a flat spot and spluttered in this range.

Other than that also I sprayed electrical silicon spray on all my sensors and coil pack plugs to get best connection. Simple things but make a difference.

Good luck sorting it.

Sent from my Samsung S3

Nope, the misfire is a new thing for me, the maps been running for over a year with no issues and the rest of the mods have been on 6 months plus with no problems. I replaced the maf to see if this would resolve the issue and bought another coil packed and tried it across each cylinder and still not resolved. There's no fault code registered to it but it drives fine and then will misfire and have no power for ten to fifteen seconds at a time, but still boosts etc when the problems not apparent.

One thought I've had is that it could be the fuel pump giving up, I've been running a 4bar FPR on it for a while (which isn't good for them as if you watch it through vagcom it attempts to reverse the fuel pump occasionally) but also after reading what now turns out to be a bad carbon canister removal guide which says to cap off the system :( I could have damaged it, when opening the filler cap at the petrol station you can hear a loud clicking noise from the pump as it depressurises I guess :S

I'm away without the car until Wednesday so when I get back my plan of action is to:

Check coil pack wiring loom

Clean up the throttle body

Fit the new fuel pump

New fuel filter

See what happens next.....

Does anyone know of any members in the Oxford area with Vagcom if push comes to shove?

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don't forget to try the NGK BKR7E plugs - you can get them for £8 on ebay and they will rule out the super 4's straight away

Worth a try for 8 quid, gap them to 0.7mm.