Hello, i need advice on my problem.

Car misfires at WOT and sometimes cannot pass 5000 rpm. I pulled 1 code - 17705 - pressure drop between turbo at intake.

Sometimes cyl 1 misfire and sometimes cyl 2. The car is chipped from 180bhp to 200-ish.

I have replaced;

1. 4 ignition coils

2. 4 spark plugs

3. Hose between the turbo and pancake pipe - with C version

4. Camshaft sensor G40

5. Timing belt and micro belt

6. Water pump

7. DV

8. Turbo unit - K03 sport

9. Silicone TIP

10. Fuel filter

11. Air filter

Only thing to do is MAF and precat wide band 5 wire lambda sonda.

I have logged MAF sensor and in 3rd gear max air flow is 144g/s but should be 170g/s according to ross tech, right?

I have also done the pressure test but could not find any leaks.

This are logs from lambda sensor;

Lambda Konst AFR RPM

0,977 14,700 14,36 3160

0,961 14,700 14,13 3960

0,93 14,700 13,67 5320

1,078 14,700 15,85 4320

0,961 14,700 14,13 3520

0,938 14,700 13,79 3960

0,945 14,700 13,89 4440

0,938 14,700 13,79 4840

0,938 14,700 13,79 5160

0,883 14,700 12,98 5600

0,884 14,700 12,99 5920

0,884 14,700 12,99 6240

0,821 14,700 12,07 6480

0,813 14,700 11,95 6720

0,813 14,700 11,95 6920

0,774 14,700 11,38 6640

Is this afr OK?

Octy Mk1 vRS AUQ.

Best regards

TBH, I can't see the maf being the cause. AFAIK, it wouldn't cause a misfire.

What spark plugs and coilpacks have you used?

Air flow does look abit low especially for a mapped engine, but as rk696 said it shouldn't be causing a misfire. Could be a blocked/ faulty injector or problem with the fuel rail.

Edited 16 February, 201016 yr by GSPK

I have changed the MAF sensor and now air flow is around 160-165 g/s but i still have misfire at WOT.

I have LPG system installed in car and same thing is happening when I run it on it so I don`t think that the problem is in fuel injectors. I suspect that the problem is in remap, maybe it is too agresive for my car.

I have also logged the injection time period and at 5720rpm time is 22ms, acording to my calculations the duty cycle of fuel injectors is 100%!! . ( if my calculation are correct)

I have original VW coilpacks and BERU spark plugs.

LPG system is multipoint injection Landirenzo Omegas.

I called my tuning shop and explaned my problem I they will install another map so will post back....

Best regards

check the plug gap first. I also have LPG and had a similar problem with a set of brand new Bosch super4's I switched to the NGK BKR7E's(colder plug so better for the gas as well) and gapped them down to .028 and it cured the missfire(lots of info about the NGK plugs on VWVortex), before doing that I changed about six coilpacks thinking they were faulty but the plug and the gap is much more important as too large a gap can actually kill the coilpacks!!!!

I can vouch for the BKR7E plugs too. I've had them fitted for the past 6 moths or so, and they haven't given me any problems whatsoever. With them being a copper plug too, they should have a better spark than the VW platinum ones, unfortunately they won't last as long though. Still, you can't have everything though I suppose

EDIT: forgot to say, the plugs I had were gapped at 1mm out of the box. I gapeed thgem down to 0.028" as karl said.

Edited 17 February, 201016 yr by rk696

I didn`t measure the gap, I screw them on straight from the box... :wall:

Gap should be 0.028? That is in inches, right? That is 0.71mm.

Thanks, will check them today and post back!

:beer: :beer:

Update;

Tuning shop has uploaded a new map and now car doesn`t misfire any more, it looks like the old map was just too much for my current setup (stock fuel injector and 3 bar fpr).

Best regards

Too much boost and too big a gap will cause a missfire, Did they check the plugs before reflashing or did they already suspect the map was too aggressive? Out of curiosity what were you boosting too on the old map vs the new map?

Both maps where boosting around 1.0-1.1 bar but this data is from vag-com, I don`t have boost gauge yet.

I have (i think) Beru ultra X Titan spark plugs.

I want to install Milltek DP decat 2.5" but I will keep the rest of the exhaust stock., is milltek worth 320 euro? ebay decat downpipes are around 200euro with shipping.

I have already P0420 Efficiency below threshold error so this is good time to remove cat, I will make the spacer for the second O2 sensor to get rid of this error.