303e30

This thread is just to inform people with misfiring 1.8t engines what might be the cause of the misfires, often new ignition coils aren't enough to solve the problem. In my family we have a B5 VW Passat and a B6 A4, both have a 1.8t and both have had misfire problems in the past. After some troubleshooting I was able to solve the problems, both cars were barely drivable and flashed the CEL.

On the Passat I narrowed the problem to bad ignition coil wires. The wires going to the ignition coils get baked from the exhaust heat and eventually crack and fail, particularly right under the rubber boot leading to the wiring connector. You can simply slide the rubber boot back and most likely the wires will be cracked, actually both the A4 and Passat had cracked wires under the rubber boots. Only on the Passat this was bad enough to cause a misfire. On both cars I redid the wires by buying new ignition coil connectors off eBay and soldering the wires into the preexisting wiring harness although I cut out a good portion of dried up wire and replaced with new wire. I used heat shrink wire so it looks almost OEM. I recommend a heat shield solution to protect the wires from the turbo and exhaust. I temporally wrapped them with some silver heat shield tape till I think of something better. Link to the new connectors I used, priced at 10$ each you will need 4:http://www.ebay.com/itm/Audi-VW-Ignition-Coil-Connector-Repair-Kit-Harness-Plug-Wiring-C106-NEW-/350726199679?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3AA4&hash=item51a8e9197f&vxp=mtr

Redone wires, the heat shrink tube makes it look like Factory wires, then wrapped with some ugly but functional heat shield tape.

The Audi A4 was slightly harder to figure out, although the wires were cracked the misfire was caused by a broken check valve in the crankcase ventilation system. I was getting codes for misfires on cylinder 1 and 3. Another code, I don't remember the code, but something to do with a pressure drop between the turbo and throttle and to check the diverter valve. I checked the diverter valve and several vacuum lines and everything checked out alright. I decided to remove the intake manifold, under the intake manifold is the PCV system which includes several large plastic and rubber hoses. There is a three way check valve going into a rubber tee, the internals in the check valve were missing which caused a massive vacum leak in the engine. I replaced this check valve along with several other PCV parts. Also replaced several other vacum lines and check lines, then I replaced the intake manifold and throttle body gaskets. I took the time to clean the intake manifold and throttle body with some B12 Chemtool Carb and throttle body cleaner. I bought the PCV components from ECS tuning, they have a good selection of PCV parts. AZautohaus.com has a decent selection PCV and vacuum parts although cheaper but not as thorough of a selection as ECS. http://www.ecstuning.com/Audi-B6_A4-...Emissions/PCV/

This is the check valve that failed:

Although already removed in the picture, circled in green is where the PCV plumbing goes. Goes from the large silver opening on the block to the small black metal tube.

Brian_Cornel

Hi. The area you have circled in green. I was fumbling around my engine and found where my hose is supposed to connect to that spot. Well, what I found was the hose was not only not connected, but split in two a couple of inches. I need to get my car to the same state yours is in in that picture.

Can you point me to any write-ups to how to do this? Or should I just start taking apart the obvious pieces until I get there. Also, do you know the part numbers for those hoses?

Thank you!

naconi

I assume you are talking about the breather hose assembly, it can be done without removing the intake. It helps to have skinny arms.

http://www.audizine.com/forum/showth...rittle-Crumbly)

I considered replacing mine with this

http://www.034motorsport.com/engine-...e-p-21950.html

but I ended up taking mine to the dealer.

Brian_Cornel

Thanks for those links. That is exactly what I needed. I really appreciate it.

303e30

I just started taking things apart, its pretty self explanatory I think. The 034 motorsport PCV kit is a better bet than the OEM pieces, it ends up costing the same but its much more durable than stock.

Martin Seebach

lol not to born blond an K&N sitting there . additional joy is CARB. just fixed ignition pin meltdown and need to reinstall for smog test. thanks in advance and how is skiing ? Tahoe is buried and way too much wind.