[mrkazoo]

I'm getting P0300 random/multiple cylinder misfires and P0301, P0302, P0303 cylinder misfires on 1, 2, & 3.

The shop thinks its definitely the coil packs and or spark plugs. I had the coil packs and spark plugs changed maybe 3-4 years back but the car's also been minimally driven (~5000 miles max during that time). Is it time to change them out again?

Is it possible these codes are caused by anything else?

 

[Zef]

Definitely not. Unless you're the luckiest (or unluckiest, depending on how you look at it) person in the world, 3 coil packs would never go bad all at once. If they did, you should go out tonight and buy a lottery ticket. Seriously.

But, since cylinder 4 is peachy, see if putting a coil pack from cylinder 3 into cylinder 4 will do anything. If all of a sudden you're getting a misfire on 4 but not 3, then it's the coil pack.

However, a random misfire code is what I believe debunks the coil pack theory. If the car sits for long periods of time, hoses (vacuum hoses in particular) could dry up and crack, causing a leak that would cause a random misfire. Since I see you also live in New England, and we just had a ridiculously brutal winter, my theory that something got brittle and cracked could easily be the root cause. Unfortunately, since the 1.8T vacuum hose diagram is the rough equivalent to an Egyptian labyrinth, finding it might be difficult.

Another test is to unplug the MAF. If unplugging the MAF eliminates the rough idle/misfires, then it's a bad MAF.

That's all I can think of off the top of my head. I'll add more later if anything else comes to mind.

 

[AndreasPassat]

Are you a 1.8 or a V6?

My cars are V6's
This reply may not apply to your problem, but it's something to consider.
My '04 when I purchased it had the exact same problem. Ultimately it was the CCT (cam chain tensioner), the CCT was collapsed. When the CCT can't open all the way and keep tension on the timing chain the intake cam actually flops back and forth as it rides over the hydraulic lifters. I was also getting cam timing error codes.

Just a side note, both of my cars have the original coil packs in them. My '98 has had the same plugs in it for almost 90k miles.

 

[mrkazoo]

Yes, mine is a 1.8t so I'm guessing the CCT doesn't apply.

I've had a smoke test done on all the lines a week ago and there weren't any cracks or leaks. The entire vacuum line system was recently replaced a few years back too so I'm fairly certain its not a problem there.

I've just cleaned the MAF too. Is there any way to see from the physical MAF if its gone bad or no?

 

[ylwagon]

Yes, mine is a 1.8t so I'm guessing the CCT doesn't apply.

I've had a smoke test done on all the lines a week ago and there weren't any cracks or leaks. The entire vacuum line system was recently replaced a few years back too so I'm fairly certain its not a problem there.

I've just cleaned the MAF too. Is there any way to see from the physical MAF if its gone bad or no?

Your 1.8T does have a cam-chain-tensioner. Regarding the MAF, watch the mass flow using VAG-COM; readings should be stable when rpms and throttle are not changing.

 

[John_E]

Another possibility is a failing ECU power relay, which can trigger all sorts of interesting error codes. This would admittedly not account for the lack of a P0304, but a wiring harness problem could.

It certainly can't hurt to clean the MAFS and the throttle body, as well as the plugs, or to swap Coil 4 with one of the others, but you really need a VCDS scan, as suggested above, to avoid blindly replacing or repairing stuff. Also, make sure you have the latest version type D coils, which are reputedly more reliable than their earlier counterparts.

 

[Emry]

I had multiple misfires and when I checked somehow the coils had moved for some unknown reason. So I pushed them back and all the misfires were instantly solved. This may not be the issue with yours but nevertheless make sure they fit tight.

 

[captain_video]

IIRC, VW had a recall on coil packs for certain model years. You might check and see if your vehicle ever had them replaced under the recall. You can probably check with your local dealer by providing the VIN number so they can look it up.

As for plugs, they should be replaced about every 50k miles.

 

[mrkazoo]

Yea, so the readings from the MAF at idle is fairly stable. It goes up and down slightly but not much. I assume minor fluctuations are fine?

On a semi full throttle run in 2nd gear, my g/s reading for the MAF isn't that great though. I got a max of ~90g/s. That's a far cry from the 150hp even with the 25%(?) efficiency power loss. But I'm not sure if that points to misfires or not.

Hmm, it definitely hasn't been 50k miles since my last replacement of the plugs. I mean, I only have 65k miles on this 14 year old car..... haha.

I'll try to do the swaps of the coils to see if that does anything. Anyone have a link to an info thread on the coils and the numbering of the banks handy? (I'll do a search on the forum as well).

FYI, I did have the recall done on the coils. Odd though that the paperwork doesn't show which banks were replaced. Did the recall blanket-replace them all?

 

[scotts13]

Did the recall blanket-replace them all?

Yes.

 

[Tomvw]

The 1.8 has only bank 1.
The cylinders are numbered from the front 1, 2, 3, 4.
The firing order is 1, 3, 4, 2.