[Beavers24]

Hey guys, new to the site here, I bought a B5 2.8 wagon about 6 months ago, just a few days ago I fired it up in the morning and it started idling real rough, then flashed a CEL at me, I shut the car off, plugged into it and got some P0300 codes, misfires on multiple cylinders. I cleared the codes and then started it again, rough idle is gone. Since then I’ve done this a couple more times to verify that it is indeed only on the first cold start after sitting for a while that it runs rough. I just replaced the plugs tonight, to no avail, I’ve read a couple threads on here with similar issues, hearing a lot of MAF talk, so I will be pulling that apart and cleaning it in the morning, but I wanted to go ahead and post this to see if any of you guys might have this experience with your cars and could point me in the right direction, thanks in advance!

 

[VAGguy]

Post more codes. P0300 is one code; random multi-cylinder misfire. Were the other codes cylinder specific misfires?

Rough idle only at cold start up is often attributed to a bad coolant temp sensor. Can you read coolant temp on your scan tool? If so, read it when dead cold and see if the coolant temp reads anywhere near ambient. That would at least temporarily rule it out.

 

[Beavers24]

Post more codes. P0300 is one code; random multi-cylinder misfire. Were the other codes cylinder specific misfires?

Rough idle only at cold start up is often attributed to a bad coolant temp sensor. Can you read coolant temp on your scan tool? If so, read it when dead cold and see if the coolant temp reads anywhere near ambient. That would at least temporarily rule it out.

Sorry about that, when i said P0300 i was just saying general misfire, there was nothing consistent about it, first time it was 2 and 5, second time it was 3 and 6, so on and so forth, always only three codes tho, multi and two specific cylinders. I will do a read on the coolant temp. As of this morning it has been running fine, no issues this morning at a cold start, like I said I did the plugs last night, maybe that did it? also cleaned the MAF sensor this morning, I did a coolant system flush this morning so cleaned some things up while I was in there. Just got done driving so it's warm now but I will check the coolant temp after it cools all the way down. I will report back with the results.

 

[AndreasPassat]

Do what VAGguy suggests.

FYI
P0300 is a general misfire code that is always accompanied by the specific P code that specifies cylinder.
P0301 Cylinder 1
P0302 Cylinder 2
P0303 Cylinder 3 and so on...

Coil pack #1 fires cylinders 3 & 5 (passeneger side)
Coil pack #2 fires cylinders 2 & 4 (center)
Coil pack #3 fires cylinders 1 & 6 (drivers side)

Seeing as the misfires are not isolated to the same coil, you can pretty much rule out the coil pack.

You mentioned cylinder 2 and 5 and then 3 and 6, those two combinations are in direct line with the firing order.
Temp sensor is a good place to start.

 

[PZ]

Is the brake pedal rock hard when you go to start the car? Have the vacuum hoses been replaced? If the vacuum or brake reservoir have a leak, the car will start rough after sitting long enough. Check the vacuum hose to the blue reservoir below the driver's side headlight.

 

[fake]

Is the brake pedal rock hard when you go to start the car? Have the vacuum hoses been replaced? If the vacuum or brake reservoir have a leak, the car will start rough after sitting long enough. Check the vacuum hose to the blue reservoir below the driver's side headlight.

what is that blue cannister? I can not find it in my repair book (Bentley)

 

[VAGguy]

what is that blue cannister? I can not find it in my repair book (Bentley)

It's a vacuum tank only on the V6. The 1.8T does not have the "blue stacked tennis balls" but instead just a ball shaped tank. ETKA is the best resource for finding part numbers and locations.

.

 

[fake]

Thanks for the info!