AudiNike12

Hi again

So I got a bunch of misfires on Cyl 4. Checked with VCDS. Can't say I notice it when I drive, but when idling I can. Nothing really heavy but still. Nothing wrong with the plug or ignition coil. I've switched positions on both of them and it stays on Cyl 4. Anything else I can check? No codes or anything. And there is 12V coming through
When I changed the valve cover gasket I noticed the cam was a tiny bit damaged/had a knock on it around Cyl 4. Have no idea if this matters or not. The thing is, I don't know if it has misfired all this time or if it's recent.

Also, I've "P0131 - Oxygen (Lambda) Sensor B1 S1: Signal too Low" code. Is it a bad sensor? And could this cause misfires?

johnkk

Not sure if 04 has ignition control modules on intake hose? If so, swap wiring to see if miss moves to #1
Could be cam. Compression test might show low compression in #4.
Is the #4 injector leaking?
.
O2 sensor is bank 1 and cyl 4 is bank 2, so probably not related.

AudiNike12

Think the ICM's are built into the coil packs. Don't know if injector #4 is leaking. Don't think so. I'll check that

johnkk

Squirt some sudsy water on the injector and look for bubbles while car is running. You might get lucky. More likely it's related to cam. I would run a compression test on bank two. Even a quickie on cylinders 4 and 5, so you don't have to pull all the coils and plugs. If 4 is low, at least you know. The "A student" would take head to machine shop...I'd just live with it.

4Driver4

Don't skip the basics. A leakdown test is also a good place to start.

AudiNike12

How do I do that?

Harleyguy

Google it. You will most likely get search result including YouTube video demonstrating the procedure.

AudiNike12

Found some videos. Thanks

Regarding the O2 sensor. I checked the resistence between pin 1 and 2 on the sensor connector and it was 10 ohms which means it's fine right? Btw, do I only have two O2 sensors on my engine? In VCDS it was B1S1 and B2S1. And I can only find connectors for 2 sensors at the firewall on the passenger side

johnkk

Resistance check doesn't mean O2 sensor is OK, only that the heater circuit for the sensor checks out.

You have 4 O2 sensors. Sensors 1 for bank 1 and 2 are the ones that signal your ECU for mixture. Sensors 2 for banks 1 and 2 check that the cats are doing their job. As I stated in prior post, your bank 1 sensor 1 is reporting a low signal. It is for your passenger side(bank 1) and would not be related to your #4 cyl misfire. You didn't note a check engine light. If the sensor were really bad, you probably would get a CEL/MIL light. I would just clean the connector and rescan to see if the code comes back. You could replace the sensor, not too hard on passenger side. Done from top of engine with fairly long extensions and O2 sensor socket. DIY info on forum. This won't solve the #4 misfire.

The first thing to sort out is #4. You've done the plug and coil swap. Next step, Injector test with soapy water. Injector will probably be OK.

For compression and leak down test, save time do Cyl 4 and 5 first on bank 2. If 4 is low, consider pulling head and having it rebuilt (or live with it). Valves and maybe cams, a good shop will know what to do. If your considering having the head rebuilt, I would run the compression and leak down test on both banks. If low or uneven, I would have both heads done.

There is a chance that the #4 injector is clogged, in which case you will have to unbolt fuel rail and pull injector to clean it or replace. Another thought would be to throw a bottle of injector cleaner in, but I've never been lucky.

One final thought. You might try a boost leak test that could locate an intake manifold leak near #4. Not too hard to replace intake manifold gaskets. Forum has lots of boost leak test info. Also, if you VCDS log for misfires on all cylinders, you might find other cylinders are misfiring, too. Vacuum leak symptoms.