Random misfiring 3000-4000rpm

[b6a4sline]

Hi guys, I just joined the Audizine forum. Hope to have a better experience then on VWQuebec hehe..

Well. as the title says.. I got some random misfires between 3000-4000rpm on high loads. Here are the codes I just scanned with my vag com:

-3 O2 sensors codes... Bank 1 Sensor 2.. nothing to worry about.
-Random Misfires
-Misfires on cyl. 1 and 3

Here are the mods I got:

-Unitronic stage 1+ (21psi boost*edit 18psi ^^)
-3" DP
-TurboSmart Diverted valve (max tighted)

No boost gauge yet.. :(

I replaced all the ignition stuff: coils, spark plugs and the wiring harness (cleaned the grounds and put new wires and shrinks). I don't know where I should look at after doing all these repairs. Maybe a vaccuum leak? Is there any simple way to check? Because I dont have a gauge because my friends at the speedshop are on vacation so I gotta do on my own during this time and this problems bothers me a lot...

I'll be waiting for your help, hope we find an issue

Thanks a lot guys!

[Seerlah]

Here is a link on how to do your own boost leak test.

http://www.a4mods.com/index.php?page=webcontent/pages/boostleak.html

You also have not tested your injectors, but I would wait on those (more than likely not the issue, but could still be). Another thing you would want to do is test your MAF, but you would need Vag Com for this. You would need to log your g/s readings for your MAF. If you are not close to the 180 g/s mark with your setup, your MAF is the issue. If you post in the regional section, I'm sure someone will be willing to let you use their Vag Com...unless you have one. If that's the case, you need to log measuring block 003 till red line going WOT in either 2nd or 3rd gear (3rd preferred).

http://www.audizine.com/forum/forumdisplay.php/252-Canada

And get yourself a boost gauge. Sheesh! Having low vacuum readings could have easily told you that you have a leak, if that is the case.

[ScratchRob13]

Check spark plug gaps, and try bringing them in a bit

Sent from my DROID4 using Tapatalk 2

[b6a4sline]

Thanks for the link. I will try this out on next weekend. And no problem for the vagcom, I already have one. I bought an old laptop just for this. Tomorrow I'll be at Eurozone's speedshop so we'll check for boost leaks.

I changed the MAF. The car is going better, but it still have an hesitation on the 4th and 5th gear at +- 4000rpm but very reduced. I vagged blocks 15-16 for misfires and no more. How can I test the injectors?

The engine has been changed for a 40 000miles one but all the around stuff is oem. So I think the injectors are a good guess.

[EverAudi]

HAVE U RUN A THROTTLE BODY ADAPTION?
ALSO 21 PSI ON UNI STAGE 1 NOT GONNA HAPPEN
UNI STAGE ONE RUNS 16 PSI.
HAVE U CHANGED FUEL FILTER AND MONITORed FUEL SYSTEM DURING LOAD ?

[b6a4sline]

HAVE U RUN A THROTTLE BODY ADAPTION?
ALSO 21 PSI ON UNI STAGE 1 NOT GONNA HAPPEN
UNI STAGE ONE RUNS 16 PSI.
HAVE U CHANGED FUEL FILTER AND MONITORed FUEL SYSTEM DURING LOAD ?

Hell you're right. 18psi exaclty. And the fuel filter sounds logical too. How can I monitor fuel system? What's the vagcom block(s)?

So here are the updates. Misfires are mostly located on cyl. 1. So we performed theses tests:

Coils swap; check.
Plugs swap, check.
Injectors swap; check. And they look clean.
Compression test: passed.
Changed the air filter box for a short ram intake. The old filter was full of dirt and shit. The car seems to be running better now, I'll have a better idea on the highway.

[b6a4sline]

Update.

Just vagged ''System too lean''. The fuel filter is ordered, I will have it fixed on monday. [up]

[b6a4sline]

So here we are.

Unpluged the fuel filter and a gross brown-red shit juice spilled off by the outlet. The filter was due for sure! Changed it, cleared all DTCs with VCDS and everything went back to normal.

So misfires DTCs + lean system = bad fuel filter [headbang]

[b6a4sline]

The lean system CEL throwed up again. Changed the first O2 sensor, nothing different. Turns out it was the injectors (maybe because the bad fuel filter made them full of dirt) so instead of paying for the same I put some TT225 and upgraded for Unitronic stage 2.

Fuel efficiency is highly improved (7.4L/100km for a 115 km drive) and the torque is more linear. Everything is perfect now, like a brand new engine.