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Discussion Starter #1
Hey everybody. Has anyone had any issues with cylinders misfiring? I'm not too mechanical so I apologize, but my S5 has been in the shop three times with an annoying hesitation on start up (after I start going it stops). The dealer determined that there was excessive carbon build up (as many on the forum have experienced), but they supposedly cleaned it out. It still had the hesitation so they had me bring it back in. Now the dealership won't let the car go. They told me that the misfires can damage the Catalytic converter and if I choose to take the car and something goes wrong then I wouldn't be covered under my warranty. Audi suggested replacing a temperature gauge as a first step. Not having my car is getting old. Any thoughts, or has anyone else found a fix? Thanks, Greg
 

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I am sorry to hear that your car is being "tested" on at the dealership. I definitely would not take delivery of the car until they have attempted at least another repair.

p.s. Has your spark plugs been replaced recently?
 

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Discussion Starter #3
Thanks for the sentiments. I believe that they did try replacing the plugs last time. They also had me use a fuel additive to try and clean out the carbon before they finally got in and dug it out manually.
 

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They may have already done this, but they should try refreshing your ECU software. I aparently had the most up to date software, and i also had hesitation on a cold start, they updated the software (same version) but it helped cure the issue.
 

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The RON rating of the fuel used is very important: It tells you the flammability, the higher the rating, the less the flammability. If you put 95RON in a high compression engine, you risk misfiring as the mixture might light-up, before the spark does so. The opposite happens in a lower compression engine that takes 95RON: put 98 and you risk the engine stalling as the sparks may not be powerful enough to light up the mixture.
 

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Discussion Starter #7
Thanks so much for all of the tips. Now I just need to convince the mechanic that you guys probably know things that he may not. They don't like to here suggestions from lay people I guess. As for fuel. In the states (maybe UK too) there is a "TopTier" listing that Audi recommends using. www.toptiergas.com. I only put Shell's highest octane in the car. It does seem to make a difference, but that might be in my head. I'll keep you updated, but keep the suggestions coming. G
 

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Hey Greg - how long have they had the car? And why are they just keeping the car? Are they actually working with AoA to deiagnose the problem or are they just scared to let it go back to you? Finally, what was your milage on the car?
 

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Discussion Starter #9
Hey Zee, They've had it for 6 days, I know that isn't a lot, but it's frustrating. This is the third visit for this issue. Audi is there today trying to help troubleshoot. The temperature sensor that they replaced didn't resolve the issue so they are on to the next idea (don't know what that is). Also, they wouldn't listen to any suggestions from me at all. The car has 25000 on it.
 

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Discussion Starter #11
Trust me, I've read all of the FSI issues but I was hoping mine wasn't impacted. Hey if they fix it and it help benefit others I'm willing to be the guinea pig. It is entirely possible that this is the first real attempt. I'm hoping to hear good news tomorrow. Maybe I've been down horse power the whole time and I'll be pleasantly surprised when I get it back.
 

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Discussion Starter #12
Well, here's the verdict. The dealership replaced the thermostat and said that that solution didn't solve the misfiring. Then they called and said that it did in fact fix the issue. I picked the car up yesterday and was told by the mechanic that it was actually a vacuum pump that was causing the misfiring cylinders and that it has been resolved. It seemed fine on the ride home, but the only thing I actually ever felt was a hesitation at start up. The strange thing is that the mechanic said that I'll likely still feel the hesitation, but as soon as I move it will stop. He also said that Audi is aware of the hesitation issue and they are working on a solution. He said that this has nothing to do with the misfiring and that that is fixed. I guess I won't know for sure. By the way, he also mentioned that the misfiring was happeneing at 2400 rpm and one other time, but I don't remember what he said. Regardless, he said that it is fixed. Stay tuned.
 

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Cylinder misfiring means the spark plug does not ignite the fuel.
Are we talking about this, or it's just wrong thread name?
 

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Discussion Starter #14
Honestly, I'm not too mechanically inclined, but the way I understand it is that the spark is firing, but not at the optimal moment. I will say that the hesitation is gone and the power seems much better, especially from 2500 to 5000 rpm. So far I'm happy with the results. I'll update if necessary. Thanks for all of the suggestions.

By the way, they also replaced my MMI knob under warrantee. I know that others have had the issue where the black plastic face mottles. I feel much better now.
 

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just reading through this it sounds as though your "misfiring" was due to a vacuum leak on the inlet manifold side or some component attached to it which would certainly result in a hesitation, hence you see better performance now.

Does sound as though there is another hesitation issue at startup that Audi are aware of. Be interesting if you can get your dealer to let you know when there is more news on this or a TSB number when Audi provide a fix.
 
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