Hi i was looking the other posts regarding missfire,bucking ,shaking and so on ,i am posting because i need help.I own a 2001 A6 4.2,and i recently replace the sparkplugs and the ignition coils but i still have trouble with it .Between 55-65mph it shakes and makes a resonance sound caused by the missfire but the computer is not registering any fault ,it stores pending codes only if i step on it above the 3500 rpm mark,the codes are P0300(random missfire detected) p0305,308,307,(missfire per ciliners 5,8,7)The cylinders are on the same bank and i tried the vacuum lines with carb cleaner , no leaks no change on idle ,guess it's ok from that point ,i have unplugged the vacuum from the fuel pressure regulator on top of the injection rail and i noticed that if i accelerate above 3500 rpm computer stores codes only for cilynder 8 and 7.Now i wonder if that is the problem or could be others.I have stock air filter ,and just cleaned the MAF (shoud be good cause if i unplugg it car runs worse)the o2 sensors are with 20000 miles on them all the rest is stock no mods whatsoever .i am running fuel injector cleaner in this tank and makes no difference nor it made 3000 miles ago. i appreciate any help on this matter .

 

Hi again,today i replaced the vacuum hoses ,siwched the injector 8 with 4 ,unfortunately the same result- missfire on the same cylinders ,same bank.i am thinking about new spark plugs ,cam position sensor or what else cause i do not have any code related to the maf or the o2 sensors ,nothing about the fuel pump or fuel regulator ,it's true that i need a vag com but since i cannot afford it at this time ,is anybody out there that can throw a bit of advice toward me ?Thanks.

 

Hi again even though nobody replied ,i am updating info in the hope that somebody will), someday! Ok now, searching the forums i found info but not exactly the one matching my symptoms so i am in the process of getting a vag com .also i wanted to say that about 25000 miles ago i did the TB job with my friend without the special tools car ran perfect ,we marked everything on the block and tried it by hand ,it aligned with the marks .Now i am wondering if we messed up the timing than the missfire will be on the whole bank not skipping any cylinders ,mine varies ,i have missfire on cyl 8,7 and sometimes 5.i will post again but i will also appreciate anything related to this matter .Thank you.

 

I was looking to the codes that the car threw in back in the days and about a year ago it had a p0348(camshaft position sensor 'A' circuit high input bank 2)since then was not driven alot and meanwhile i erased the codes .could somebody explain if the code means to replace the sensor or could be more stuff that triggers it , i also remember that some "electrician " tapped in the car harness about that time to install a ignition interlock .any help is appreciated .thanks in advance !

 

I just came from the car ,i replaced the cvv(crankcase vent valve) it the diapfragm was blown,but i still get the missfires ,i was planning on playing with the lemmywinks and see any changes,is there anybody that can help with the original codes just in case i screw up?The vag com says just :

Chassis Type: 4B - Audi A6 C5
Scan: 01,02,03,08,15,16,17,35,36,37,45,55,56,76

-------------------------------------------------------------------------------
Address 01: Engine
Controller: 4D0 907 560 AE
Component: 4.2l V8/5V G01 0003
Coding: 07752
Shop #: WSC 09111
WAUZL64BX1N092250 AUZ7Z0Y1638649
3 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16692 - Cylinder 8 Misfire Detected
P0308 - 35-00 - -
16691 - Cylinder 7 Misfire Detected
P0307 - 35-00 - -
Readiness: 0000 0100

Any thoughts or ideas about what can be the problem ?

 

You checked the plugs, coils and injectors. You are not getting any cam position codes. You checked the vacuum. If all done correctly, next thing to do is to check the compression.

 

Hi , and thanks for the reply Hxgaser ,i will ceck that too.i was playing with a unnisetings program and it feels like the car runs a bit better than it used to so i'll ceck the compresion and then the timing ,i just noticed that it missfires a bit less after playing with it and starts missfireing at higher rpm.thanks again for the reply.

 

What is a unnisetings?

 

It's a program, Lemmiwinks or another ,bosch unisettinggs, the ones that alows you to tweak fuel trim, rpm ,and and acouple more things but all is without a map and at your own risck .

 

Hi again it seems that the road that i took in order to diagnose the missfire was longer for me .today i cecked compression and i got 180 psi per cylinder so i have compression and that led me to look under the tb cover and for my surprise i discovered the tb verry loose (you could twist it verry easy with your fingers ) so i ordered a tb kit and tools ,i'll keep writing if that is not the problem but i think that other than that i'll ceck the fuel pressure regulator .Thankx again Hxgaser for the input and if you know any tricks for the tb job i will be happy to listen.