Cylinder Misfires and system too lean. Causes???
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  1. #1
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    Exclamation Cylinder Misfires and system too lean. Causes???

    Hey everyone. So I have a 2002 Volkswagen Passat 1.8L turbo with four cylinders. It has 160,000 miles and I just bought it a few months ago. The prior owners took wonderful care of it and the carfax shows every single time they took it to the dealership to get maintainence which was all the time. Unfortunately, unlike the prior owners I'm a pre-med college kid with a very small budget so I'm trying to figure this out on my own since I live 6 hours away from home. My check engine light has been on for a few months and the code has always been system too lean bank 1. Now I realize I should've got. It looked at but again college takes priority so not much money is left for my car. Well, my inspection is coming up so I figured I would have my friend clear my codes and when he did he saw that there were other codes that said cylinder misfire 2, cylinder misfire 3, cylinder misfire 1, random multiple cylinder misfire. I thought that was weird because my car has been acting great. A few days ago, my car started to act really weird and it's now undriveable. My check engine light started flashing and I looked that up and it said that that means the cylinders are currently misfiring. I left it at my friends on the side of the road because I read that you can't drive it if it's misfiring. I don't know what would cause all these codes. I hope someone can help me. I replaced all the coils and it made no difference. I also checked all the spark plugs and they look fine. I don't know what else to do that I can actually do myself. Please help me!!!!! I'm treading having to have it towed to a dealer

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  3. #2
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    check for any vacuum leaks and you could try to clean the mass air flow sensor which may be your problem. i had a 1.8 in the shop a few weeks ago running terrible, full of misfire codes and a lean code. new mass air had it running perfect again

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    As stated, check for vacuum leaks, probably the "L" hose and the nipple right at the front of the intake manifold. Replace all hoses with high temperature silicone. Then check to see how the car is running by clearing the codes. See if anthing comes back.

    Leaving a lean situation for long periods of time can cause issues with your Catalytic Converter.
    Last edited by GSO_Passater; 09-25-2011 at 06:47 PM. Reason: spelling

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    I would also suspect a coil pack has gone bad.

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    Quote Originally Posted by PZ View Post
    I would also suspect a coil pack has gone bad.
    Even after he replaced them?

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    Thank you all for your responses! Im going to check into cleaning the MAF tomorrow and let you know what happens.

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    Please check the vacuum hoses first. It is time to replace them and a vacuum leak can cause misfires. It is cheaper than the MAF.

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    x2 on vacuum hoses, its cheaper and easy to fix in the first place. The ones under the manifold can easily be missed so be sure to look on it further and check tightness of the hose clamps on your check valves towards the pcv valve and the connection to the manifold or better replaced those one time use hose clamps with a regular one from your neighborhood auto parts store . A simple way to diagnose even by just looking at it is to look if your hoses is simply soaked with oil then most likely you have the leak in there. Running lean doesn't damage your cat anyway its just cause drivability issues well running rich does cause it will fried your cat. From your symptoms alone I can see you have a pretty huge leak in there.

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    Quote Originally Posted by VAGguy View Post
    Even after he replaced them?
    Yes, there may still be a bad one in there.

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    Motel Room Moderator VAGguy's Avatar
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    Quote Originally Posted by PZ View Post
    Yes, there may still be a bad one in there.
    I realize the possibility, but if he has a lean code and multiple random misfire, I would move onto the next thing. possible Vac leak thru the small lines, suction jet pump, L hose, or PCV.

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    Yeah, but he has had those for a while. The rough running/flashing CEL is usually a coil, but he may have lost an intake hose.

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    Correction to everyone who's said he...I'm a girl haha anyways I finally gave in and had it towed to a local European place. He was super knowledgable and it ended up being the vacuum hose!! It was one of the intake ones. That's all it took and my baby was back to normal. Thank you so much for all the replies! You guy are great!

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    Quote Originally Posted by VAGguy View Post
    I realize the possibility, but if he has a lean code and multiple random misfire, I would move onto the next thing. possible Vac leak thru the small lines, suction jet pump, L hose, or PCV.



    I would have swore it still had a bad coil.

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    Quote Originally Posted by Patriotsbabe89 View Post
    Correction to everyone who's said he...I'm a girl haha anyways I finally gave in and had it towed to a local European place. He was super knowledgable and it ended up being the vacuum hose!! It was one of the intake ones. That's all it took and my baby was back to normal. Thank you so much for all the replies! You guy are great!
    I guess we should have looked at the user name. My son is a Patriots fan too.

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    Motel Room Moderator VAGguy's Avatar
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    Quote Originally Posted by Patriotsbabe89 View Post
    Correction to everyone who's said he...I'm a girl'!
    I knew that .....then I read other responses and forgot....my bad.

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    Same issue with my '05 1.8. I have new plugs and new coils. So where can I find info about where all the vacuum hoses are? I love pictures.

    The codes are random misfire and misfires on all four cylinders. No lean codes.

    You all rock!!
    Last edited by battmanf16; 03-06-2012 at 10:30 AM.

  18. #17
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    If you have no lean codes, unlikely to be a vacuum leak. Have you cleaned MAF sensor?

    Also,

    Quote Originally Posted by PZ View Post
    Yeah, but he has had those for a while. The rough running/flashing CEL is usually a coil, but he may have lost an intake hose.
    After a botched attempt at swapping PCV lines, idle was so rough my normally solid CEL would flash if I idled too long (i.e. long stoplight). Temp fix was to plug off line coming from intake manifold, you'll see tomorrow PZ.

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    My misfire began after some cracked hoses were discovered by my local mechanic and were replaced. The car went in for a coolant leak from somewhere around the passenger's side of the engine but out of sight. (I'm still not sure where it was leaking.). What vacuum lines are on the back or side of the engine which would not be visible from above?

    Thanks for the info so far.

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    Passenger side out of sight is likely coolant flange or coolant temp sensor that sits in top of the flange. There aren't vac lines down there - only chance would be if he bumped something loose while reaching down. Regardless, on an '05 you should have the durable rubber vac lines, not the braided ones OP probably had on an '02...really doubting vac line.

    What were the cracked hoses, and I presume they were replaced by said mechanic? I'd start by cleaning the MAF sensor, no lean codes imply there is not a vac leak.

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    Doyle, thanks for the information! You rock!

    Yes, he replaced the vacuum hoses. I had a 94 Passat with the old braided lines - which were terrible. I just thought these might have been in a hotter part of the engine. But I really don't know. It's just odd that it went in to the shop with no history of a misfire (except when a coil pack needed replacement) and came out with one. I will clean the MAF after I get it back from the shop -- it started leaking again a week after the initial repair. Ya I know...bummer.

    Thanks again! Bob

  22. #21
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    Well, I'm certainly not the most knowledgeable guy - but if they were only working on a passenger side coolant leak, not sure how that tinkering would result in all 4 cylinder misfires AND no lean code. Especially if it's not running rough, could just be dirty MAF acting up and timing is coincident.

    Does the mechanic not know much about VWs? Might not want to keep using him if not, strange you have to diagnose on your own.

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    The mechanic seems to say all the right things about VWs. He worked on a buddy's B5 (timing belt R2) and did great. He's a good dude. And yes, he is checking the codes. I just had access to an Innova 3130 code reader and checked it myself while on the road immediately after it happened. It has only thrown the codes once since replacing the plugs with new NGKs 75 miles ago.
    Last edited by battmanf16; 03-09-2012 at 01:55 PM.

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    My mechanic is replacing the flange this weekend as I go out of the country for two weeks. We'll worry about the misfire once the leak is fixed. Thanks! You have been very helpful. I looked up your other posts about changing the flange. Not an easy task. Wow.


    Update: I have returned from overseas. My mechanic could not fix the leak.

    I took it to the dealership. They replaced the flange...leak gone. Additionally, they fixed the misfire. (Only this past weekend did we get some more codes in addition to the "random misfire" -- 0411, 0507, and 0171) It seems several of the vacuum hoses along the intake manifold were broken near the attach points -- like they were forced out of the way and cracked.

    Bummer that we had to take it to the dealer, but the backyard mechanic was unable to help. Sometimes, you get what you pay for. Truthfully, our dealer is FANTASTIC. I was just trying to avoid the $96/hour shop rate. But in this case, it was worth it.
    Last edited by battmanf16; 04-08-2012 at 03:59 PM.

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