Unable to log misfires with VAG-COM. What am I doing wrong?

**Spanky** · 10-19-2008 03:46 AM

I've been having a few misfire issues recently but when checking blocks 15 and 16 in VAG-COM the fields are always blank (not showing zero, just blank). All the other blocks give readings, just not the ones for misfires. Checking at idle or when driving around makes no difference and logging both blocks over a few minutes just results in a bunch of commas in the log file...

I can definitely feel the engine misfiring at idle and under load so surely it should be possible to log this using VAG-COM? I'm new to the software so perhaps I'm doing something wrong.

I have the latest release of VAG-COM with the official Ross-Tech cable. I also checked using a friend's laptop and a different cable but it was the same.

Anyone have any ideas?

**AudiSportB5S4** · 10-19-2008 04:42 AM

have you downloaded the latest software? also, did you install the drivers and everything correcly? the software is up to 805.something

**Spanky** · 10-19-2008 04:58 AM

I'm running the very latest version (805.1) that was released a couple of days ago. I've tried it with older versions as well, even with a different cable but it made no difference.

**Mark@AutoSpeed** · 10-19-2008 07:43 AM

What ECU is in the car? You are probably running 8D0907551C or D? In that case misfire detection is not activated in the car from the factory.

**Spanky** · 10-19-2008 09:50 AM

Thanks Mark, that explains everything!

My ECU is indeed 8D0907551C. I guess there's no way of activating misfire detection in my car then??

**Mark@AutoSpeed** · 10-19-2008 05:01 PM

It is possible, just not very easy. Basically in the ECU code you can enable the routines and then need to point the data to the correct blocks so that VAG COM can effectively read the data. To do this you need a fairly high level of understanding of Motronic and Disassembly.

What code are you running now?

**Spanky** · 10-20-2008 03:20 PM

Thanks for the info, but based on what you said this is definitely way out of my league. I don't even have a basic understanding of Motronic and Disassembly.

Forget it man, I guess I'll live without the misfire detection. Time to start replacing stuff, I just hope it doesn't bankrupt me. I'll begin with the spark plugs and go from there...

**Rated S** · 10-20-2008 03:31 PM

Originally Posted by Spanky

Thanks for the info, but based on what you said this is definitely way out of my league. I don't even have a basic understanding of Motronic and Disassembly.

Forget it man, I guess I'll live without the misfire detection. Time to start replacing stuff, I just hope it doesn't bankrupt me. I'll begin with the spark plugs and go from there...

If you have a friend nearby with a non-misfiring b5 s4, try swapping out the coilpacks with them. That would be the cheapest (free, or maybe a beer for your friend) way, then spark plugs, etc.

Also try looking at the sensors on top of your airbox (should be 4 2 brown and iirc 2 grey) and make sure they are all plugged in securely. Try swapping that airbox piece with a friend as well. Also you can pressure test to see if there is a leak, boost/vac leaks love to make misfires if they are in the wrong place.