Stuttering After Idling For A Few Seconds - 3.0 AVK

[SJorge3442]

So I've been battling all sorts of issues with misfires and lean codes for a while now. After swapping the fuel pump which I thought to be the issue, I still had misfires on my drivers side bank. 4,5,6 every time. Then my car FINALLY threw a code for the front O2 of the drivers side. Swapped that out and all has been well.....until today. Leaving a red light or anywhere else where I've been stopped long enough to idle a few seconds, I'm getting a slight hesitation when accelerating. Its only in first gear and it goes away after I reach 3K RPMs. Now, last week I swapped injectors around thinking I had an injector issue, when really it was a coil pack issue. While I am waiting for one replacement coil (Running R8 coils) I have my drivers side bank running on 3 old coils and my passenger side bank all on R8 coils. Im throwing no codes and I don't think the issue is really a misfire issue. Could the mismatched coils be to blame? Could I have distriburded the o-rings on the top of the injectors which is now causing me not have a solid seal around the injector. I'm getting no smell of fuel and I'm on a stock tune FWIW.

[SJorge3442]

Anyone?

[cschuster]

Well, mine has always done something similar. If it sits at idle for a little while, sometimes the idle drops, causing a slight vibration. Touching the gas makes it go away instantly. When the car drops back down to idle, its smooth for another 20 seconds or so. Never touched the injectors, coils have over 100k on them, plugs have 10k, vacuum lines/PCV upgraded, ect. No codes until recently - got a lean code and a purge valve code that are very intermittent. I can clear them and they don't come back for a week or so. No hesitation while accelerating though...haven't gotten around to ordering a purge valve to see if this fixes it.

[SJorge3442]

Well, mine has always done something similar. If it sits at idle for a little while, sometimes the idle drops, causing a slight vibration. Touching the gas makes it go away instantly. When the car drops back down to idle, its smooth for another 20 seconds or so. Never touched the injectors, coils have over 100k on them, plugs have 10k, vacuum lines/PCV upgraded, ect. No codes until recently - got a lean code and a purge valve code that are very intermittent. I can clear them and they don't come back for a week or so. No hesitation while accelerating though...haven't gotten around to ordering a purge valve to see if this fixes it.

Purge valve? Not sure im familar with that. I'm starting to think that its because im running mismatched coils. One side of the engine is running more efficient that the other. The issue didnt appear until I swapped the coils. The feeling is almost like when you get bad gas. Actually, now that I think about it. I was in the middle of bumblef*ck recently and got gas at a no name place. Maybe its just that?

[cschuster]

It's part of the evap/emission system. Fuel in the tank vaporizes, some of this excess vapor is stored in a charcoal canister. When told by the ECU, the purge valve opens, allowing gas vapor stored in the canister to be sucked into the intake manifold for combustion. If this valve sticks open for whatever reason, the symptoms are the same as a small vacuum leak. Rough idle, hesitation, ect. In my case, I think its sticking open, but very slightly. Enough to cause a slightly rough idle, but not enough to have a code all the time. We have 2 of these valves, one on top of the air filter housing, and another on top of the throttle body by the vacuum lines. I don't know the difference between the 2 at this time.

Anyways, swap the coils and see if the misfires switch banks? Have you checked the breather hoses and shit around that bank?

[SJorge3442]

It's part of the evap/emission system. Fuel in the tank vaporizes, some of this excess vapor is stored in a charcoal canister. When told by the ECU, the purge valve opens, allowing gas vapor stored in the canister to be sucked into the intake manifold for combustion. If this valve sticks open for whatever reason, the symptoms are the same as a small vacuum leak. Rough idle, hesitation, ect. In my case, I think its sticking open, but very slightly. Enough to cause a slightly rough idle, but not enough to have a code all the time. We have 2 of these valves, one on top of the air filter housing, and another on top of the throttle body by the vacuum lines. I don't know the difference between the 2 at this time.

Anyways, swap the coils and see if the misfires switch banks? Have you checked the breather hoses and shit around that bank?

Ahh. Makes sense the purge valve you speak of is part of the EVAP system.

I'm getting 0 codes, so swapping the coils isnt going to help since theres nothing to track. Breathers lines are all heater hose and properly secured and the vacuum lines are all silicone and according to Torque(i know not accurate but I keep an eye on it) steady and strong above 20lbs at idle.

[cschuster]

Have you monitored vacuum during the misfires? I've got a Ross tech cable you can borrow that may provide more data

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[cschuster]

And by codes, if it's the coils, then swapping sides would give you misfires on 1, 2, and 3.

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[SJorge3442]

And by codes, if it's the coils, then swapping sides would give you misfires on 1, 2, and 3.

Sent from my Nexus 5 using Tapatalk

Yeah right now I have no "hard" misfires. I know it takes a bit to trigger misfires, so maybe it is indeed misfiring without throwing a light for it. I don't have legit VCDS (had lite and then 2 laptops died and I havent upgraded to a legit cable yet), so that might be helpful to check.

[SJorge3442]

Ended up replacing all 6 coils (again) and all is well. Note to self. Don't use tunes from people who won't tell you what they changed. Clearly there is something up with the tune if I continue to blow coils. Stock ECU is back in and not being swapped again.