Rough Idle at traffic lights.

[audi_nicoya209]

Hey everyone so since about June 2013 I have noticed that after driving around town for a while my engine starts to idle rough once i come to a red light which annoys the hell outta me. I keep a sharp eye on my rpms and they stay steady it just idles rough the whole time I'm waiting for the light. As soon as the light turns green I give it gas and it smooths out and runs fine no hesitation cutting out or anything. I already replaced the spark plugs and wires and it didn't solve the problem. My spider tube is broken and taped up with electrical tape in front of the intake manifold and the crankcase vent system itself is original still. My vacuum lines have never been touched either so maybe something is broken cracked or something?

Thanks

2001 Audi A6 Avant 2.8 quattro 180,600 miles

[schaefer921]

could be anything at this point, a bad check valve or even a bad coolant temp sensor, rev it a little at the stop light. try to trigger a CEL, i had a similar problem with my b6, took about two months and finally it tripped a CEL, it was my coolant temp

[audi_nicoya209]

could be anything at this point, a bad check valve or even a bad coolant temp sensor, rev it a little at the stop light. try to trigger a CEL, i had a similar problem with my b6, took about two months and finally it tripped a CEL, it was my coolant temp

I highly doubt it's the coolant temp sensor cuz I don't have any problems with restarting a hot engine and my temp needle moves normally. Might be worth mentioning that it does it only during city driving and not at every single red light. It will be fine one light or two then rough idle the next and repeat. If I drive long at a single speed then no idle issues. I'm really tempted at buying vacuum hose and just go thru the whole thing replacing what's needed. Like I mentioned driving around its fine.

[mlzervas]

Does it change if you shift into neutral? It sounds like a torque converter on the way out. It may not throw a code, but if it does, it may show up a 0741. Mine is a 3.0 but it had the same symptoms, it shuttered at rest, rpms didn’t change, and drove fine.

[zchrist88]

Hey everyone so since about June 2013 I have noticed that after driving around town for a while my engine starts to idle rough once i come to a red light which annoys the hell outta me. I keep a sharp eye on my rpms and they stay steady it just idles rough the whole time I'm waiting for the light. As soon as the light turns green I give it gas and it smooths out and runs fine no hesitation cutting out or anything. I already replaced the spark plugs and wires and it didn't solve the problem. My spider tube is broken and taped up with electrical tape in front of the intake manifold and the crankcase vent system itself is original still. My vacuum lines have never been touched either so maybe something is broken cracked or something?

Thanks

2001 Audi A6 Avant 2.8 quattro 180,600 miles

I'd bet money its the crankcase breather hoses or your vacuum lines. Replaced mine a couple of months ago and this solved my problem. Might as well plan on replacing all. Your lines and hoses are most likely very brittle at this point. The small breather hose is a real pain to get to but at least its a cheap fix. Let me know if I can be of further help.

http://www.ebay.com/itm/VENT-TUBE-98...8dc87c&vxp=mtr

[audi_nicoya209]

Does it change if you shift into neutral? It sounds like a torque converter on the way out. It may not throw a code, but if it does, it may show up a 0741. Mine is a 3.0 but it had the same symptoms, it shuttered at rest, rpms didn’t change, and drove fine.

no it still rough idles in neutral

I'd bet money its the crankcase breather hoses or your vacuum lines. Replaced mine a couple of months ago and this solved my problem. Might as well plan on replacing all. Your lines and hoses are most likely very brittle at this point. The small breather hose is a real pain to get to but at least its a cheap fix. Let me know if I can be of further help.

http://www.ebay.com/itm/VENT-TUBE-98...8dc87c&vxp=mtr

you know I been toying around with the idea of the rubber vacuum lines. I have the crankcase breather kit brand new in a box but I've been putting it off cuz I need to remove the intake to replace some coolant gaskets (another story lol) and I've read on a good write up on passatworld dot com that those need to be disconnected so I figured do everything at once. My breather hoses that go over the front of the intake did break while I was changing out my plug wires (more brittle than an egg i swear smh) so I went ahead and put it together with electrical tape. One thing i noticed was some dry bacon grease stuff oozed from the breather tube connector on the passenger valve cover as well as the bends and stuff its not alot tho just a lil bit. I do have oil leaks too so that's why I bought the breather kit in the first place

[zchrist88]

Rubber vacuum lines are fine. That bacon grease is condensed oil vapor. When you go to pull out the crankcase breather hose you'll probably notice a lot of build up in certain areas. You really don't want to leave electrical tape on there for very long because the high temperature could cause the tape to corrode and cause further problems. Also, you're probably running rich or lean at times which is giving you bad gas mileage.

Before you go to do this please note that you must have both pieces to the kit! When you go to pull this thing out its going to basically disintegrate both hoses. I did not know or expect this and ended up waiting an extra week for the part to arrive. Also, you'll want to pull up a DIY on removing the throttle body BUT DO NOT REMOVE THE THROTTLE BODY. Following steps will give yourself the room to reattach the smaller breather hose.

[audi_nicoya209]

Rubber vacuum lines are fine. That bacon grease is condensed oil vapor. When you go to pull out the crankcase breather hose you'll probably notice a lot of build up in certain areas. You really don't want to leave electrical tape on there for very long because the high temperature could cause the tape to corrode and cause further problems. Also, you're probably running rich or lean at times which is giving you bad gas mileage.

Before you go to do this please note that you must have both pieces to the kit! When you go to pull this thing out its going to basically disintegrate both hoses. I did not know or expect this and ended up waiting an extra week for the part to arrive. Also, you'll want to pull up a DIY on removing the throttle body BUT DO NOT REMOVE THE THROTTLE BODY. Following steps will give yourself the room to reattach the smaller breather hose.

I was told not long ago that my right bank was running lean (related?) and yes my gas mileage is horrible not scary scary bad but its bad. The kit I have in the box does have the hose that goes into the back of the engine that you mentioned along with the green check valve suction pump and clamps. Also the other day I was working on my coolant temp sensor (trying to replace gasket no success) and when I went to remove the intake elbow for more room I accidentally bumped the little canister looking connection (where the hose divides into the suction pump and smaller hose into the crankcase below throttle body) on the breather tube almost near the suction pump and I know it's cracked but I noticed that a little bit of funky smelling water came from there. Is that normal? It wasn't a gusher but some droplets that when I touched them with my finger I took a whiff and it smelled weird like something I've never smelled before...

[zchrist88]

Do you think it could be coolant?

[audi_nicoya209]

Do you think it could be coolant?

I'm not sure but now that coolant has been brought into the subject I do have a coolant leak from my rear coolant pipe under the intake manifold where the rear coolant pipe connects behind the thermostat. I discovered that leak in mid May 2013 and I started having issues with the rough idle in early to mid June 2013. Do you think its possibly related somehow? Also this past Sunday I swapped out my battery for the correct one cuz I had been running the battery that came out of my moms old junked out chrysler town & country minivan cuz I was in a pinch at the moment I needed the battery. After the swap I did all the resetting steps and also allowed my throttle body to cycle itself before starting it. So far I haven't idled rough and the car also has been having more get up and go. Fingers crossed.

2 things is the coolant leak affecting something? And second this is one of the moments I really really wish I had a vag-com -__-

[autlaw]

my 2.8 had this exact same problem, turned out to be a coil on the way out. I replaced the coil pack and that resolved the problem.

[audi_nicoya209]

my 2.8 had this exact same problem, turned out to be a coil on the way out. I replaced the coil pack and that resolved the problem.

hmm good point I've never touched the coil pack and I'm assuming its still original. Will take a look into that as well

[zchrist88]

I'm not sure but now that coolant has been brought into the subject I do have a coolant leak from my rear coolant pipe under the intake manifold where the rear coolant pipe connects behind the thermostat. I discovered that leak in mid May 2013 and I started having issues with the rough idle in early to mid June 2013. Do you think its possibly related somehow? Also this past Sunday I swapped out my battery for the correct one cuz I had been running the battery that came out of my moms old junked out chrysler town & country minivan cuz I was in a pinch at the moment I needed the battery. After the swap I did all the resetting steps and also allowed my throttle body to cycle itself before starting it. So far I haven't idled rough and the car also has been having more get up and go. Fingers crossed.

2 things is the coolant leak affecting something? And second this is one of the moments I really really wish I had a vag-com -__-

I don't think it will idle rough until you start driving again and your ecu starts to overcompensate or undercompensate for your leaking lines. Resetting your throttle body isn't going to be a permanent fix. I would at least replace the hoses and lines you know are bad. This is pretty routine preventative maintenance that will save you in the end.

As for the leak, I'm a bit confused where its coming from. If it's part of the crankcase breather hose then that means your engine is mixing coolant and oil vapors which can happen if you make lots of short trips without letting your engine warm up and burn this off. However, usually its more of a milkshake texture than water...

[audi_nicoya209]

I don't think it will idle rough until you start driving again and your ecu starts to overcompensate or undercompensate for your leaking lines. Resetting your throttle body isn't going to be a permanent fix. I would at least replace the hoses and lines you know are bad. This is pretty routine preventative maintenance that will save you in the end.

As for the leak, I'm a bit confused where its coming from. If it's part of the crankcase breather hose then that means your engine is mixing coolant and oil vapors which can happen if you make lots of short trips without letting your engine warm up and burn this off. However, usually its more of a milkshake texture than water...

I was looking at the vacuum diagram under the hood (a bit intimidating to be honest) and it says they are color coded. Are they really?

I'm going to try to snap some pics this weekend and post them here for you to see.