Oil leak, rough running and misfire

[Ncie Gyu]

So.. i've got a 07' a4 avant 2.0tfsi. About two weeks ago i noticed a burning smell when i parked in my garage for the first time in a long while, guess i catched the smell easier because it was inside since i noticed it had been leaking alot/for a long time. I decided to drive back into town a few days later to buy what i needed to clean it up, when i did that CEL came on and i checked the fault code with my ob2 and got P0303 (misfire cyl. 3). Drove it back home and notice that the oil leak seems to start from the rubber hose circled in the picture. Seems to be going from the vacuum pump to the brake booster. Took it out and i couldn't see any oil inside it surprisingly but i notice a whole lot of small cracks. on both ends of the pipe.

Doesn't explain the oil leak though so while waiting for a friends mechanic to look at it i've changed out the pcv valve ,breather tube and switched over to summer tires. After doing that and clearing the code the CEL went off and i didn't get a code anymore. But the car started running very rough, idle is bad but not jumping up and down or going too low but it almost sounds like a diesel and i feel like it's vibrating more. Test driving it i can feel the engine shakes/vibrates quite bad between 2000-3000 rpm. Going over 3krpm it feels just like normal, speed doesn't matter so im not thinking it's wheel related. Not being sure if the cracks in the vacuum hose is enough to cause a boost leak, i tried using starter gas around it while idling the engine and it didnt rev up or do anthing. I've changed out all spark plugs, ignition coil on cyl 3, oil and oil filter, air filter, fuel filter. Test drove it again today and got the CEL again and fault code P0303.

The vacuum pipe is around 70$ where i live so before spending more money that might not solve the problem im trying my luck here maybe someone have had a similar problem! Still a couple of days away till the mechanic will look at it..

[Theiceman]

the vacuum pipe of which you speak is to the brake booster only. and comes from the vacuum pump . Although it is unlikely this has anything to do with your misfire cell, it is probably likely you disturbed something in that area and have a different kind of vacuum leak.

it is also very unlikely that the hose of which you speak has an issue . A VERY common problem on these cars is the vacuum pump it is attached to is leaking. Audi even came out with a newer revision of this pump to correct the situation. ( This is likely why you saw no oil inside it , it is not leaking , its the pump and migrating over the outside. ) You are correct though that's an expensive piece so be careful with it as it is hard brittle plastic and will break. if you have confirmed it is actually leaking at the connection I would just look closely at the rubber piece and maybe try a new clamp. Again this is NOT related to manifold vacuum. Turbo cars ( without going into deep explanation ) require a vacuum pump for the brake booster and it is a simple system. vacuum pump driven off intake cam, hose, brake booster.
I think you need to look somewhere else for your misfire.

[Ncie Gyu]

the vacuum pipe of which you speak is to the brake booster only. and comes from the vacuum pump . Although it is unlikely this has anything to do with your misfire cell, it is probably likely you disturbed something in that area and have a different kind of vacuum leak.

it is also very unlikely that the hose of which you speak has an issue . A VERY common problem on these cars is the vacuum pump it is attached to is leaking. Audi even came out with a newer revision of this pump to correct the situation. ( This is likely why you saw no oil inside it , it is not leaking , its the pump and migrating over the outside. ) You are correct though that's an expensive piece so be careful with it as it is hard brittle plastic and will break. if you have confirmed it is actually leaking at the connection I would just look closely at the rubber piece and maybe try a new clamp. Again this is NOT related to manifold vacuum. Turbo cars ( without going into deep explanation ) require a vacuum pump for the brake booster and it is a simple system. vacuum pump driven off intake cam, hose, brake booster.
I think you need to look somewhere else for your misfire.

I just applied some electrical tape around the cracks and put new clamps on. The rubber hosing into the vacuum pump have some play i can kind of wiggle it back and forth but seems to be the same for others so might not be an issue.

It's really hard to see back there and there's so much oil that i can't clean out that i can't tell if it's leaking anywhere else, it's never leaking upwards is my presumtion..

Just reinstalled the breather tube and pcv valve thinking the shaking started after i changed them. They seemed fine and didn't change anything of course. Don't really know where to go from here could the leaking vakuum pump be causing the misfire/shaking?

[Theiceman]

I just applied some electrical tape around the cracks and put new clamps on. The rubber hosing into the vacuum pump have some play i can kind of wiggle it back and forth but seems to be the same for others so might not be an issue.

It's really hard to see back there and there's so much oil that i can't clean out that i can't tell if it's leaking anywhere else, it's never leaking upwards is my presumtion..

Just reinstalled the breather tube and pcv valve thinking the shaking started after i changed them. They seemed fine and didn't change anything of course. Don't really know where to go from here could the leaking vakuum pump be causing the misfire/shaking?

no as mentioned, oil leak has noting to do with misfire. sounds like a manifold leak. are you running vcds ? are there any other codes? is it still misfiring on one cylinder ? did you try swapping coils ?

oh the loose connector into the pump is just an oring . but you need a new vacuum pump and it will have all new parts , that's where all the oil is coming from , your assumption of oil not migrating up would be fine in a vacuum with gravity only . but you are shooting through the air at 70mph , the air currents do strange things with oil ..

the most general things for misfiring is coils and plugs for sure but troubleshoot first , try and find out if it is one cylinder, or if it is a global issue affecting multiple cylinders.

[Ncie Gyu]

no as mentioned, oil leak has noting to do with misfire. sounds like a manifold leak. are you running vcds ? are there any other codes? is it still misfiring on one cylinder ? did you try swapping coils ?

oh the loose connector into the pump is just an oring . but you need a new vacuum pump and it will have all new parts , that's where all the oil is coming from , your assumption of oil not migrating up would be fine in a vacuum with gravity only . but you are shooting through the air at 70mph , the air currents do strange things with oil ..

the most general things for misfiring is coils and plugs for sure but troubleshoot first , try and find out if it is one cylinder, or if it is a global issue affecting multiple cylinders.

Im ordering the new revision pump right now. I've installed new NGK spark plugs and swapped coils around, still cylinder 3 misfire. It's the only code and all i have is a cheap ob2 wifi reader..

[ahotboy15]

that nice you change parts and cause more problems.

[Theiceman]

Im ordering the new revision pump right now. I've installed new NGK spark plugs and swapped coils around, still cylinder 3 misfire. It's the only code and all i have is a cheap ob2 wifi reader..

ignore the Troll, the rest of us do.

interesting that it stays with cylinder 3 even after swapping coils and plugs I ( I am assuming you gapped the plug correctly ) so it leaves a couple of things, but can I ask you to verify a couple of things.

When EXACTLY did the misfiring occur, did you change parts because of the misfire ? or did you change parts because of the oil leak and THEN the misfire started ? if that's the case I would double check the flex hoses that goes to the pcv and make sure they did not fracture and that they are clipped on tight.

the misfiring could be worse on cyl three but I don't want to jump to the conclusion it is ONLY cyl three as you are not running VCDS.

Based on your response we can go from there , but I will give you a few general idea.

usually misfires are caused by lean condition ( not enough octane causing predetenation ) , check all your hoses and connections very carefully and see if you are drawing any air.
Check the wiring to your injectors and coils as wiring harnesses become brittle with age , especially three.
Did you fill up recently ? could it be bad gas ?

some starting points

[ahotboy15]

Bad gas? Thats a good one

[Hugh@EuropaParts]

Bad gas? Thats a good one

It happens... click here

[ahotboy15]

Figures...Jersey

[00redrt]

That misfire could be an injector... happened to me and swapped all af them for once...

[Ncie Gyu]

ignore the Troll, the rest of us do.

interesting that it stays with cylinder 3 even after swapping coils and plugs I ( I am assuming you gapped the plug correctly ) so it leaves a couple of things, but can I ask you to verify a couple of things.

When EXACTLY did the misfiring occur, did you change parts because of the misfire ? or did you change parts because of the oil leak and THEN the misfire started ? if that's the case I would double check the flex hoses that goes to the pcv and make sure they did not fracture and that they are clipped on tight.

the misfiring could be worse on cyl three but I don't want to jump to the conclusion it is ONLY cyl three as you are not running VCDS.

Based on your response we can go from there , but I will give you a few general idea.

usually misfires are caused by lean condition ( not enough octane causing predetenation ) , check all your hoses and connections very carefully and see if you are drawing any air.
Check the wiring to your injectors and coils as wiring harnesses become brittle with age , especially three.
Did you fill up recently ? could it be bad gas ?

some starting points

I sort of had some maintenance time with my car after i got the CEL and misfire the first time. I tried cleaning out the oil that had leaked from behind the vacuum pump, then i also changed the pcv valve and breather tube because of the misfire, i also swapped the coils and then i test drove it. After doing that is when i also noticed the big vibration between 2-3000rpm (and engine sounding like a diesel). All though the CEL is off and i dont get a fault code anymore. I'm saying it's only misfire on cylinder 3 because p0303 is the only fault code i get. Not sure how it works though but could there be more cylinders misfiring without fault code? What i also tried was buying a new ignition coil and only swapped cyl 3 (after allready swapping them around i still couldn't help but try). I've heard they go bad on these engines so thought it would be something to have done any ways. Should i buy 3 more and swap the rest out? Or can i wait for my wallet to get thicker if that's unlikely to help my case..

The only thing i've found looking around all the wiring, connectors and plastic tubes is the plastic surrounding the wiring to the iginition coils. The wiring looks completely fine but the plastic have been broken ever since i bought the car. Even the plastic "nail" that you need to push in order to get the connector out of the coil (on cyl 3) is missing but im able to put them all in place. Could this be an issue? Can provide a picture later on how it looks

Tomorrow im gonna remove the vacuum pump and see if anything got cracked or damaged when i tried to clean the oil out from behind there.

[Ncie Gyu]

I always put only $20-30 in the tank and i just put another 20 in when test driving it cause the gas was really low, so the "bad gas" should probably be out by now then if that was the case...

[Ncie Gyu]

The only thing i've found looking around all the wiring, connectors and plastic tubes is the plastic surrounding the wiring to the iginition coils. The wiring looks completely fine but the plastic have been broken ever since i bought the car. Even the plastic "nail" that you need to push in order to get the connector out of the coil (on cyl 3) is missing but im able to put them all in place. Could this be an issue? Can provide a picture later on how it looks

pic 1 there's a crack but i can't see any damage to the wiring
pic 2 however the pin is missing on this connector to secure it in place. There is no "click" when i push it in but it looks like it still stays in place.
pic 3 i just spotted that the pins are missing on 2 of my coils, so i have 3 coils not "clicking" in place. I've done this alot of times before and im always very careful in removing these connectors so i don't think this is something that broke when i tried switching the coils around. Definitly will be replacing all coils and looking for new connectors, not sure if there are different models but in Sweden i can only find the connectors on different tuning sites stating the connectors is for "VAG COP" ignition coils. Don't know what COP means but they look the same

[Ncie Gyu]

Update:

Because i like to see more people do follow ups on their issues posted online, i will do the same.

Problem was a clogged/faulty fuel injector on cylinder 3. Took about 5 hours to fix. Just replaced it and car runs like new again.

[flowhigh]

Update:

Because i like to see more people do follow ups on their issues posted online, i will do the same.

Problem was a clogged/faulty fuel injector on cylinder 3. Took about 5 hours to fix. Just replaced it and car runs like new again.

......

[Ncie Gyu]

And the oil leak was of course the vaccuum pump, arrived home to day looking forward to some backbreaking work

[Theiceman]

Great job , lean condition caused by bad injector. Did you have to pull the intake to do it ?? Did you carbon clean while you were in there ??


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[Theiceman]

And the oil leak was of course the vaccuum pump, arrived home to day looking forward to some backbreaking work

Just gonna replace it ?


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[Ncie Gyu]

Yeah, it's alot of things that needs to go. We followed this guide it was pretty straight forward with pictures and all. From page 28 http://www.stasisengineering.com/sit...ongitudial.pdf

Just going to replace the vaccuum pump. I know you can also try changing the o-ring but after looking at where it's placed it's not a job i want to do again, and for most it doesn't seem to solve the leaking for long..

[Theiceman]

you will be a pro at the vacuum pump by the time you are done lol , I can do it in less than 10 minutes now sadly ..