maciekb2002

I have s4.
Lots of work done to it.
When I got it Car had misfire got it fixed, T-belt was off 1 tooth on bank 1 .
That was 3k ago since then car run like a champ.
About Last week I started filling little misfire. No check engine codes.
Two weeks later car misfires 80% driving time.
I installed new plugs, replaced all coil packs , no oil leaks to spark plug holes,
Smoke test done no vacuum leaks at all

I have very sensitive boost gauge and every time I drive car easy that stays on the vacuum it runs super crappy.
As soon as I step on it . Goes right up to 18psi and pulls like a mad man , no misses at all.
All the symptoms look to me like vacuum leak , but where.
I pulled intake pipes twice to look for leaks.

What is better part that when car gets hot and I park it for 30 mins it will start running smooth for like a 20 miles and then misfire comes back but slowly and gradually .

I am lost . I think that I will try to replace igniters mounted on air box.

I am using reg code reader to pull codes.

Help

maciekb2002

I meant by sensitive boost gauge on vacuum side you can see needle movement
every time when car misfires

P0234

http://www.audizine.com/forum/showth...res?highlight=

maciekb2002

Rechecked all the vacuum lines again.
And install new ignition modules,
The same crap .
Pattern repeats.
Runs like crap in the morning.
Let it sit for 30 mins when is cold and it runs great for 30 mins and later misfire comes back

maciekb2002

Let it sit for 30 mins when is hot and it runs great for 30 mins and later misfire comes back

P0234

Are you actually troubleshooting or just tyring to "get it done" ?

"Random Misfires
Random misfires are as a rule much harder to diagnose. Do not try to diagnose random misfires if you still have cylinder specific issues. Since you’ve already done a boost leak test from above (you did one right???) the next step is to really figure out if the motor thinks it is running rich or lean. Without a vag-com or OBDII reader that streams live data, you are out of luck. Common issues are air leaks but we’ve already eliminated those in our first tests. Next, and fairly common are aging primary 02 sensors, the rears do not have anything to do misfires. As they get old, 02 sensors start reading lean and try to richen up the mixture. Dieing MAF sensors also cause mixture issues, you can unplug it and see if the misfires change. Old/Bad plugs can also cause misfires at idle but you will notice power issues up top also. Various tunes/injectors can also cause misfires at idle."

Checking vacuum lines and a boost leak test are totally different. Once you make sure the intake tract can hold pressure, next thing to do is datalog the car to figure out if it is running rich or lean. Likely its lean as it runs fine when cold (and enriched), again leading to an air leak. You need to look at your fuel trims and evaluate those.

maciekb2002

I have some more info about my misfire.
I cleaned my MAF , big hitachi 3,5'' housing.
Car started idling around 1300 rpms.
Checked 02 sensors reading while driving , voltage in specs.
Went to my friends shop and we did throttle body adaptation .
Car had also code for high idle.
After work was done car drove like a dream for 50 miles.
One day.
Then problem started to coming back.
Also we had to try adapt throttle several times there was an error coming out.
I am assuming that Throttle body is my issue.
I will clean it really good before replacing it.
And regressed all the little gears on the side, visual check too .
I'll keep you posted

maciekb2002

So after changing complete PCV system nothing changed.That cost me more then part that was broken.
I did more vacuum leak tests and smoke tests . Nothing was showing.
So after almost 2 month I know what is the problem.
If your car has a little misfire on vacuum and then if you step on a throttle pedal it disappears your throttle body is shot.
The best way to check it is by removing it.
You need to used good amount of pressure to make throttle plate move.
After you open it a little it will want to close as soon as you release the pressure.
If there is any free play between gear that drive that plate , you need to replace you TB.
Mine had about 1-1.5 mm of free play .
After installing fresh one car runs like new.

Good luck guys.

Shoken audi is the place to get parts , good , checked with 6 months warranty