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Billy, Trainer/ Master Technician
Category: Audi
Satisfied Customers: 3498
Experience:  Trainer 8+ years, master tech. 10+ years, SAE member
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Audi TT Quattro: Hey mike, I own a 2001 audi TT Quattro 6 speed

Customer Question

Hey mike, I own a 2001 audi TT Quattro 6 speed 225 hp, it's got the AMU engine. So the problem I'm having is every once in a while after I've been driving it for a couple hours it develops a misfire. Sometimes it doesn't happen for hours and just develops while I'm driving, and then sometimes if I've driven it and shut it off for a while, say come home and let it sit for a bit, then try to go to the store a couple hours later it has the misfire when I start it. I know it could be spark plugs and coils but the coils are only a few months old and the plugs as well. I put brand new supercoils in it and they're supposed to be high performance. It has various upgrades, ko4 rebuilt frankenturbo, 550 cc injectors, Evolution motorsports cold air intake, catless downpipe by 42 draft designs, high performance borla exhaust, southbend racing clutch etc. I was wondering if it might be a vacuum leak because you'd think if it was a coil it would misfire every time I start it up? Just trying to get a
Submitted: 2 years ago.
Category: Audi
Expert:  Billy replied 2 years ago.
Hello and Welcome!
I'm Billy and i will assist you with your inquiry.
Feel free to ask if any further info is needed.

It could be a vacuum leak, and it also could be one of the coils, or even the plugs, and it could be anything else... We need to diagnose correctly, and should be able to pinpoint the fault.
Honestly, it's all the upgrades that i'm worried about... When did the problem start, and did start before you upgraded the coils?
Were any parts replaced immediately prior to this misfire?
Are you sure this is a misfire, and not some hesitation from the engine?
Does it do this only at idle, or at different rpms, and if yes, is there a specific rpm where the misfire is at its peak?
Customer: replied 2 years ago.

No it started after the coils were upgraded. It seems like a misfire, it's like it's only running on 3 cylinders or something. And it does it at idle and under all rpms it stays until I shut the car off and let it sit for a while. Then I restart it and it's gone. Sometimes it never happens till its been shut off for a while after running it, then I start it up and it has it again. There were no parts replaced right before it started happening. The last thing that was put on before the problem occurred was the catless downpipe and borla exhaust. Maybe it's a bad o2 sensor?

Expert:  Billy replied 2 years ago.
Hello Seth,

It could be a bad O2 sensor... however, first do you have the old coils, so you can install for checking?
Customer: replied 2 years ago.

Yes I do. So you want me to try putting the four old coils back in and see what happens?

Expert:  Billy replied 2 years ago.
Indeed Seth, as i've seen many problems resulting aftermarket coils.

Try the old ones, and we'll take it from there....

Kindly get back to me with your findings, so we proceed accordingly.

Customer: replied 2 years ago.

Ok I'll put them in and check the spark plugs while I'm at it and see what happens and then let you know. The only problem is I might have to drive it for a bit to get it to start doing the misfire since it doesn't always happen right away.

Expert:  Billy replied 2 years ago.
Take your time...

I will be waiting for your findings... Best of luck for now!!

Customer: replied 2 years ago.

So far it seems to be running right it hasn't done the misfire again. I've been trying to drive it around to make sure it's totally gone it just has been much cooler the last couple days so I was kind of waiting to see what happens when it gets back in to the high 90s again.

Expert:  Billy replied 2 years ago.
Hello Seth,

Take your time, make sure and get back to me... Good luck for now!