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Discussion Starter #1
Hello, I'm looking for help finding the cause of a Cyl #5 misfire. I'm getting code P0305 Cyl.5 Misfire Detected and P0300 - Multiple Cyl. Misfire detected. I looked at blocks #15 and #16 and I see that at Idle cyl #5 is misfiring repeatedly (about 20 times per minute, worse when the engine is cold), and I have a slightly rough idle. Others are zero misfire at idle, but if I rev the engine I can get 1 or 2 misfires on Cyl 2 and 3.

I saw other threads pointing to bad plugs and wires. I swapped my wires #5 and #6, and plugs #5 and #4 (and #5 and #6) but it made no difference. Since the ignitor coils are shared between cyl #5 and #3, I don't think there is a coil problem.

I'm thinking that vacuum leaks or a TB problem wouldn't cause a single cylinder problem at idle. Has anyone out there seen a single cylinder misfire due to vacuum leaks or a dirty TB?

My car is a 2000 V6 ATQ. Thanks for any help.
 

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ICM is not on a V6.

So you've swapped the plugs and swapped the plug wires and there's not change?

Not too familiar with a V6, but the next thing to do is swap the coil, even though it's shared with cyl 3.

But you shouldn't get "1 or 2 misfires on cyl 2 and 3" when you rev it. In truth, you are getting misfires on multiple cylinders. My bet would be overall bad plugs or wires, so that even swapping the plugs and wires doesn't help, 'cause your just swapping out a weak plug/wire with another weak plug/wire.

How did the plugs look? How many miles on them? If your car is a 2000 - it's six years old. If it were my car, I would replace the plugs and plug wires regardless - IMO it needs them anyway so it's not a waste of money even if it doesn't fix the problem. Then, with fresh plugs and wires, if that doesn't fix it, you can more easily isolate the problem.
 

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I don't have a good explanation of your cylinder 5 misfire but I think you should go ahead and replace your Spark plugs, vacuum lines with silcone and do a TB cleaning anyways. That is unless you have done all those things recently. All of that can be done in a couple hours and needs to be done anyways. After you swap the coils I would think The ignition wires at a $135 would be the next thing to replace. I don't remember the resistance but you can use and ohm meter to test them. good luck
 

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Discussion Starter #5
My car has 47K miles, and I replaced the plugs and 40K service items at 38K. I can take the advice to clean the TB, replace the wires due to age, and throw in a few new plugs too just for good measure.

It isn't clear to me how to swap the coil shared by cyl 3&5 with another coil since all three coils are mounted to a single hard wire ingitor unit - is there a tested way to do this?

Thanks for the advice so far.
 

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Plug wire x2. I got a cyl 4 misfire and a new plug wire fixed it. A bad coil would show up on 2 cylinders so its either the plug or the wire. If you search "cylinder 4 misfire" my thread will come up. Our resident VAG tech Sharkey swore it was the plug wire and he was dead on.
 

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Discussion Starter #9
I used NGK BKR6EKUB when I changed the plugs 10K miles ago. I believe this is the OEM V6 plug.

Even though swapping plugs and wires didn't change the situation I'm willing to give new wires a shot since it seems to be the #1 misfire problem and a single cylinder misfire seems to me most likely ignition related.

On the other hand I don't see why swapping the bad plug/wire to cyl 4 or 6 didn't cause misfire on those cylinders.
 

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Rusty said:
ICM is not on a V6.
Not one to argue with Rusty :lol: but they sell an ignition control unit for the V6 over at getcoolparts. Hope this link works, if not do a search for part number VWW075763 it's a Beru unit and here's a pic of it.
 

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MOS said:
I used NGK BKR6EKUB when I changed the plugs 10K miles ago. I believe this is the OEM V6 plug.
Yeah those are the right plugs to use, and they should never fail after 10k unless something else is wrong. Possible wires, but like you said swapping things around should move the misfires.
 

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VWTreads said:
Not one to argue with Rusty :lol: but they sell an ignition control unit for the V6 over at getcoolparts. Hope this link works, if not do a search for part number VWW075763 it's a Beru unit and here's a pic of it.
Doh! :)
 

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I suspect after additional research that this ICM for sale at some places online that lists as a V6 part is incorrect. I read that the ICM is integrated into the Ignition coil pack on these 30v V6 engines and it can be had for about $130 over here hope this helps. So I guess what I am trying to say is it's probably something failed in this unit since the coils and ICM are all inclusive.. Good thing it's not really much more than just an ICM.
 

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Discussion Starter #14
It turns out my problem was with the throttle body and maybe dirty fuel injectors.

I replaced most of the vacuum lines and tested the rest with a vacuum guage, but I still had the cyl #5 misfire. Next I cleaned the throttle body, and it really cut down the misfire rate, but I still had a few misfires on the block #16 counter. Finally I poured a bottle of 3M fuel system cleaner from Napa into the tank, and a couple of days later the misfires were gone. I've been code free for a week of smooth idle driving since then. As others have reported throttle response is much better, and the car drives like new again. I've learned that throttle body cleaning is a regular maintenance item on the V6.

The the throttle body cleaning was much easier than I expected. All I had to do was:
1) Unscrew both clamps from the flex hose leading from the air intake, and remove it. No need to open the filter box.
2) Unclip the three electical connectors above the throttle body.
3) Unscrew the three bolts holding on the vacuum solenoid mounting plate and shift it to the side. No need to unhook any vacuum lines.
4) Unhook the PCV hose from the throttle body with a screwdriver as the prybar on the clamp
5) Use a hex key to start turning the bolt on the throttle body and remove it with my fingers.
6) Pull off the angled hose from the throttle body and clean with solvent soaked towels.

By the way Rusty, I'm going to replace my plug wires tomorrow. As you said they are pretty old, and on top of that one of my connectors broke from all the swapping of cables I did. The deal on cables for the V6 is at www.1stvwparts.com - only $100 for all six OEM wires. Thanks for all the help.
 

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Glad you got it figured out! I think you have learned some valuable maintenance lessons. It's a very good idea to run fuel system cleaner through the car about twice per year. Throttle body is notorious for gunking up and causing issues on our cars. I think since it's on the back of the engine it's often out of sight and out of mind. Also that's not a bad price at all for OEM wires, I'll remember that when I need new wires.
 

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good find on those wire I am going to replace mine soon and that is by far the best price I have seen. glad you finally got to the bottom of your misfire.
 
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