The Dreaded Misfire Stays With Me

[Trampdrifting]

Ok, I'll start by saying thanks to all of those who helped out in the last post, but I thought I'd start fresh and clear up what I've done already

Octavia 1.8T VRS (AUQ)

It has a random misfire and holds back between about 2400 - 3000 RPM

Throws no relevant fault codes up on the reader

So far I've:

Replaced MAF

replaced N75

Replaced all four coilpacks

Checked for broken/damaged cables on coilpack wiring harness

Replaced plugs with BK7RE

Checked and found no boost/Vaccum leaks

(All replaced with Silicone)

Cleaned throttle body

Replaced inlet manifold gasket

Used plenty of injector cleaner

Run only on 99 octane

Replaced fuel pump

Replaced fuel filter

Replaced FPR

Replaced both Lamda sensors

Is there something I'm missing or is that not pretty much the entire list of things that could possibly cause this misfire?

Please help.........!!!! :(

Edited 6 July, 2013 by Trampdrifting

[Gtiracer]

Well it sounds a pretty comprehensive list that's for sure, one thing to mention is that even though the hoses are in good condition, if the any jubilee clips holding them on are loose or worn then potential boost leak could escape from there without being obvious.

But that aside a place such as r tech would be good to give it a dyno run and they would probably be able to help you out, they must've seen every Vag engine issue under the sun

[Trampdrifting]

That's true, I think they know everything there is to know about the 1.8t, but about the hoses etc, everything's plumbed together nice and tight, I've had plenty of boost leaks previous to this with the standard pipework, and this is a totally different feeling. It holds full boost perfectly if your planted, but it just splutters around that rev range. I'm just loosing the will to live with it, I'm frantically trying to track someone down with Vag Com in the Oxford area so they could run some live logs. But not even getting any luck with that :(

[Adamweal]

What about a trip over to clive @ cntuning right nice bloke knows a hell of a lot and will fix it

[Decender]

First thing I would do is get someone log some measuring blocks to see what certain things are doing, MAF readings, fueling, lambda, boost etc and go from there. I had the same problem with mine recently and it ended up being a combination of dodgy MAF, Fuel pump and extremely weak actuator. Would have never got to the bottom of it if I hadnt had someone check the measuring blocks out. Also get a leak test done and see what that throws up.

[demonufo]

Just to point out... it's certainly not that unusual to find a bad plug straight out of the box. Sadly I don't have a decent plug tester any more. :(

[Trampdrifting]

From the plugs point of view I took the Bosch super 4s out and replaced with the NGK's, and apart from feeling smoother to drive the problem itself hasn't changed in any way, so I've ruled out it being a plug problem. It's clearly over fuelling as the old plugs look like coal and you can still smell it pouring out the back. When it's in limp mode (from the first cold start) it drives perfect with no hesitation, but as soon as you reset it and boost starts to kick in the hesitation happens

Edited 7 July, 2013 by Trampdrifting

[demonufo]

You certain that your injectors are in tip top nick? And have the right injector nozzles fitted?