yyalli

Hi All,

My 2007 A3 2.0T (about 120K miles) is getting a misfire problem.

On my regular visit to an audi dealer to replace engine oil, they recommended to replace spark plugs and I accepted it. After that visit, my car started getting a misfire problem on a cold start and engine light was on.

The mechanics told me there was "sporadic misfire" and recommended to use high-end fuels (I used Sams's club gas) and just put an "audi fuel treatment" (an additive). I emptied the tank and filled up with high-end fuel they recommended.

But, I still have the problem; at cold start, the engine shakes for about one minute and gets idle when running.

My question is:
i) Can the spark plug replacement in the dealer shop be a cause of this problem? Can I blame the dealer shop for this problem?
ii) Is using Sam's club gas so bad? I always used premium gas (octane 93) though.

I looked over this forum and found many posts about misfire. I am getting worried about this problem. It may require a serious money to fix. I am planning to do the following things by myself first:
a) put fuel engine additives (sea forms, Chevron Techron Concentrate, etc)
b) replacing spark plug again and ignition coils

I really appreciate any advice or recommendation.

Thanks,
Jong

Rennsprt805

If I had to guess I'd suggest checking the spark plugs. The plugs have a ceramic insulator and if it is fractured [by poor handling], it'll cause a mis-fire.
Also I'd check the routing & condition of the wiring for the coils. If there's a pinched or intermittent short a mis-fire is possible.

It's unfortunate that the dealer didn't provide better service and resolve the issue...

djbrkb

hi, I also own a higher mileage 2006 a3 2.0. I have had a similar problem as well for the past few months and believe i have finally solved it.

after trying a bunch of things i can tell you what has improved the condition and then finally solved it..

1) remove carbon build up on intake valves. look for a "diy to sea foam an audi 2.0 engine" there are a bunch of great how to's out there that make it easy. it made a noticeable improvement.. Although paying a shop or dealer to remove the intake manifold and clean it properly (which if you have the $500-600 to spend) is really the best way to go.. FYI i have never had it done professionally.

2) replace cam follower on the high pressure fuel pump. This is a weak (and inexpensive - $45) part on our cars.. do some searching and you will find many fail at about 60-80k miles. if this is allowed to completely wear out till it disintegrates, it can ruin both the intake cam and the fuel pump ($$$$) - so it is best to replace this every 50k miles or so.. as this part wears out it does not "push" the fuel pump plunger in enough which reduces fuel to the chambers which throws an engine fault... I just changed mine a few weeks ago. it had 68k miles on it and it was worn pretty well.
I was convinced that this was going to solve my check engine light! while the car idle and acceleration noticeably improved, the check engine light came on the next day.. !@#$ - anyway, changing this part regularly is the right thing to do..

3) check the MAF (mass air flow sensor) which is built into the air intake tube on the engine cover.
the wire harness that plugs into the back left corner of the engine cover is it. the actual sensor is located inside the tube. I found out that over the years of service on my car, the harness had been damaged and one of the wires leading to the connector had an intermittent connection. I repaired, cleaned and reinforced the wire harness at the connector - and HOLY CRAP!!!! car runs, idles, accelerates like brand new!!!! Two weeks now - no engine light and it runs like a top!!


Obviously i cannot guarantee that these will fix your car - but, all three are easy to check and cheap to do yourself if you are a bit handy. If not, take this info to your shop and ask their opinion and have them check into these things.

Also - I own a vagcom tool which is really great at looking at scanning the car computer, reading the specific faults and gives good guidance on what to look at next.. they cost $250

Good luck.

yyalli

Thank you so much for the advices.

After cleaning and re-inserting the coil packs, the engine check light has gone for a few days (but, I still observed a rough engine start when it was cold) but the engine light came back again yesterday.

I checked MAF. It looks like MAF is not working (I pulled the MAF connector but the engine runs ok). I am planning to clean or replace it.

One thing I am wondering now is that, why is this problem happening only when engine is cold? Engine starts smoothly when it hot. Maybe I don't feel misfire during the drive?

I will check other things (spark plugs, sea foams, cam follower) and keep them posted.

Thank you again for your advices.

Jong

djbrkb

Hey Jong,

my car was doing the same - rough idle when cold - better, but not perfect when hot. I also noticed the car was not starting as quickly and easily as it used to.

the engine will continue to run if you disconnect the MAF harness - it will at first stumble if you disconnect while running, and will run a bit rough if left disconnected. once disconnected it may throw a fault and the engine programming will go to a default mode to keep engine running but will no longer continuously optimize air-fuel mixture because it "sees" no airflow. in this state the car runs ok but not great.

just last week another new thing happened to my car.. on the highway the car started cutting out randomly while under accel at about 4500 rpm.. threw another code and lit the check engine light. when i ran vagcom later that day it said intermittent signal from engine crank sensor. I looked online again for the location and change procedure - fortunately it is easy to get to (right next to the oil filter on the front of the engine), and held in by one bolt. I bought a new one for $70 and put it in.. FIXED - the car runs great like it used to - but the idle - especially when cold is better... Hmm, trying to understand why this would help or if it is just a coincidence.. I guess if the crank sensor is old and worn out (like mine) it can work intermittently and screw with the smooth running if the computer is not seeing the crank turning properly?? and is that cold and hot related? maybe?

anyway - you may want to get an opinion of this as well.

Oh, another thing i replaced that i just remembered.

There have been at least three revisions of the PCV valve which is on the top front of the engine. My car had this replaced once under warranty when it was two years old. this was the last time this area was touched and it was by the dealer. I since had read that the valve was revised again to a third design so i bought one and did it myself (again this is an easy install). when i removed the PCV i noticed the breather tube that comes out of the front of the PCV and goes down into the lower engine block was all cracked open where it connects to the PCV valve. the crack was big and the tube was noticeably brittle. not sure if this causes a vacuum leak which would affect idle and acceleration. the tube cost $35 and went in easy.. I would check the age, revision, and breather tube of the PCV valve if you havent already! My local dealer keeps both the PCV and tube in stock if this is any indication..

iamaudihere

I had the same issue last year after i changed my spark plugs.turned out that i needed dielectric grease on the coils to make a good contact.
if the coil/spark plug are cold in the morning they will not make a good contact until they warm up an expand.
hope this helps