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Old 12-11-2011, 05:38 AM   #1
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Default Multi Cylinder Misfire. Violent shaking. 1999 Audi A8

I recently bought a 1999 audi for $1k. It has 190k miles..

when acclerating at different mpg..sometimes 40. sometimes 45. sometimes 50..etc. .. there is a VERY VERY VIOLENT SHAKING.. feels like the car is going to shake itself apart. Steering wheel doesnt really move that much. but by taking foot off gas, the shaking disappears. If I put foot back on gas immediately the shake is still there. If i let the car coast for a few secs and then put foot back on gas the shake is gone..

seller said timing belt and water pump were replaced a "recently" but i may have to verify that by checking myself.


engine seems to be strong.. still responsive and punchy. except for the shaking and...

ALso. multi cylinder misfire.. on idle and low rpm there is a NOTICABLE MIsfire.. I hooked up obd and have misfire on 4,5,1,7,2
I bought new coils and the cheap ngk vpower plugs and have misfire on 4,5,1,8.. Weird thing is that the Check engine light never came on.. wont come on.. Nothing.. its like someone disabled it.. disconnected the


Can someone help?

i have pics of cv axles. control arms.. ect


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Old 12-11-2011, 06:12 AM   #2
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On your year car, the check engine light is a replaceable bulb in the instrument cluster that can burn out (and they do)...on 2000 and up, it's an LED built into the speedometer.

Multiple misfires are often associated with a timing "jump" (belt usually)...need to check belt/valve timing...could have been installed out of time or jumped due to bad tensioner or improper installation.

Power output stages (ignition modules) usually fail 1 side at a time...either cylinders 1-4 or 5-8...not out of the question, though worth checking...but misfires on both sides are more often a timing problem or something associated with timing (engine speed sensor? ...not very likely, I think).

Control arms: The rubber bushing end (inside) often looked cracked well before failing, but the ball joint end with a torn boot will fail in no time..no repair of that boot or joint...arm replacement only.

CV boot (on axle shaft) needs to be replaced ASAP, unless you're already getting clicking or steering wheel oscillations...then the CV has already failed. If the joint is not gone, the boot/grease can be replaced with a $25 kit...otherwise many replace the entire axle/joints with aftermarket axles (acceptable, but NOT the quality of OEM, which are high $$).

Joint service when replacing boot only (does not include getting axle in and out of car...see Bentley manual):

http://forums.quattroworld.com/a8/msgs/45872.phtml

You have multiple issues to deal with and before flooding forums with questions (OK one at a time ), and searching for online tutorials (some of which you will NOT find), I highly recommend getting a manual...if you don't have that tool in your box, you are not equipped to work on your own car:

http://www.ecstuning.com/Audi-D2_A8-...anuals/ES6279/
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Old 12-11-2011, 06:38 AM   #3
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Default multi cyl misfire

simple problem to fix. Pre facelift A8's have seperate output stage for coils. sorry you waisted money on new coils. Those coils are controlled in part by output stages located under plastic by your washer fluid fill. pull off plastic and remove bracket. You will see two output stage controllers. remove and swap you will confirm problem cuz the other four cly will now mis fire. Get part numbers and do research for best price. I got new one for $55 landed. use thermo paste (like for computer cpu)to secure to bracket for best heat transfer. Your picks have nothing to do with YOUR REAL problem. Your half shafts are best replaced as whole new. check local rockauto and ebay. look cose at the output shaft seals to make sure they are not leaking. your already in there and easy to replace. Around $40 for seal. Regardles check the front diff fluid level there is level plug at the right front side of your ZF5HP24. I have the right front seal I'll sell you for $30 incluing USPS shipping. Pm me if intrested. A8's are a labor of love. I have had 3 pre facelift and currently own two 2000s.

$
Quote:
Originally Posted by darrelljr00 View Post
I recently bought a 1999 audi for $1k. It has 190k miles..

when acclerating at different mpg..sometimes 40. sometimes 45. sometimes 50..etc. .. there is a VERY VERY VIOLENT SHAKING.. feels like the car is going to shake itself apart. Steering wheel doesnt really move that much. but by taking foot off gas, the shaking disappears. If I put foot back on gas immediately the shake is still there. If i let the car coast for a few secs and then put foot back on gas the shake is gone..

seller said timing belt and water pump were replaced a "recently" but i may have to verify that by checking myself.


engine seems to be strong.. still responsive and punchy. except for the shaking and...

ALso. multi cylinder misfire.. on idle and low rpm there is a NOTICABLE MIsfire.. I hooked up obd and have misfire on 4,5,1,7,2
I bought new coils and the cheap ngk vpower plugs and have misfire on 4,5,1,8.. Weird thing is that the Check engine light never came on.. wont come on.. Nothing.. its like someone disabled it.. disconnected the


Can someone help?

i have pics of cv axles. control arms.. ect


Photobucket


Photobucket


Photobucket


Photobucket


Photobucket


Photobucket


Photobucket



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Old 12-11-2011, 07:51 AM   #4
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So I double checked the outout stage cyl assignment. one controls cyl 1,4,6,7 and the other controls 2,3,5,8. passanger side bank is 1,2,3,4 and drivers side is 5,6,7,8. So you can see one output stage dose not control one bank. I would make sure your spark plug gap is set to .32 I ran into problems with random misfires with brand new plugs and too wide a gap. I would still swap output stages and see what happens. After some more consideration I am very concerned with your tourqe converter as root cause of your shake. You describe your shake it is not speed or RPM dependent. After your engine is smooth as silk. I would drop the trans pan and change the trans filter. You can get Fk355 filter and gasket kit from Oreilly auto parts for less than $30. I use light torque of 55in/lbs on pan cuz it is a rubber gasket not paper like factory. I have used Valvolines Max Life Fluid. Meets "LT" lifetime audi specs and you can buy it cheep at walmat. I know this is a huge point of controversy. Hate to see you pump a bunch of money into car that may need expensive trans work. Audipages.com is a great source for solid info.
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Old 12-11-2011, 08:15 AM   #5
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ill drain a few inches of trans fluid right now and post pics in a few mins...
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Old 12-11-2011, 08:26 AM   #6
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i meant a few ounces..
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Old 12-11-2011, 08:57 AM   #7
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Look before you leap! You need a solid plan to refill your trans before draining anything. I use a easy to find "orange fluid transfer hand pump" you can find them anywhere. along with a peice of 3' clear tube from lowes insert into the orange tube and clamp both tubes together. Insert a 6in section of solid copper wire stripped from romex. you can kink and create "j" to hang into fill tower. then you can fill trans with all 4 wheels on garage floor and you by the drivers door. Careful when replaceing tower plug cuz your car should be running in neutral. Block wheels Duh LOL. Cat is very hot. You will need 17mm allen socket. Bought mine at autozone pack of 3 sizes less than $15. Break loose tower plug with breaker bar. There is a drain plug on trans. So you can do drop and fill. Maybe good idea regardless because it can help eliminate low fluid as cause of problem. Then when you change Trans filter your final fluid will be far cleaner than with just filter change. Don't be discouraged if drop and fill dose little to nothing. Real problem could be dirty filter causing problems with fluid flow and ultimately creating problem with lock up funtion in torque converter. Could be time for Trans rebuild. I would not address any other problems half shafts etc. till you eliminate likely trans issues. Of course You still need to eliminate any engine missfire issues FIRST. Simple... rule out most obvious and cheepest before moving forward. Multiple misfires at shifting could make ECU and TCU do crazy things.
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Old 12-11-2011, 09:04 AM   #8
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Here is the fluid.. Im almost ashamed to post this.. I got the car 2 weeks ago.. I was going to do the fluid in a few weeks and let the car sit.. but since i got the extra nod from win72010 i drained it.. Im usually really good about changing fluids especially when i buy cheap cars..

here it is


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Old 12-11-2011, 12:04 PM   #9
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When I buy a car I assume all fluids need replaced or at least topped off. That said your ZF5HP24A has Diff fluid at rear of trany and at the front. Also "lifetime" fill of amber colored trans fluid. Dark fluid is associated with clutch wear and heat. There are 4 magnets that are going to be full of shavings. Think of them as sponges. They can only hold so much before the filter has to catch the rest and then cause restrictions. I still stand firm on confirming your spark plug gap. On 4 valve 4.2L engines I like the NGK platinum the design is simple and smart with a fine wire electrode normally found on much more exspensive irridium plugs. careful gapping to .32 Go ahead and use plastic safe contact cleaner on output stage conections and swap them. Double check ground conections. Make sure you don't have vacuum leaks. Your engine should be running smooth. One Problem solved with little out of pocket. Drain and fill trans fluid you will need 6 or 7 qts. Order your filter kit then another 7+ qrts. Walmart sells the Maxlife in gallons. I replaced the factory pan bolts that use torx and used 6 x 20mm along with HARDENDED 1/4 washers. That will spread load and not distort the pan. With a rubber gasket like in Fk355 use 55 in/lbs and your golden with either bolts. Make sure you understaand Paul W's work on audipages.com before you attempt. learn from our blood sweat and tears lol. Good news is that as far as A8's go.... $1000 is a good price car to cut your teeth on.
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Old 12-11-2011, 01:43 PM   #10
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IF you're gonna do the atf/filter change, gotta do it right...not a simple drain and fill...gotta follow procedure or you won't get the right level....exactly like this...no deviations:

http://www.audipages.com/Tech_Articl...servicing.html

You can only get the level correct with engine running, correct atf temp, following going through gears in the proper sequence and car dead level.

Personally (and opinions vary), I would address the misfires FIRST...ONE cylinder misfiring can feel like a trans coming apart.

MANY firmly believe messing with a high mileage trans in these cars that has no issues, is asking for trouble...including an atf change...the new atf can wash away material that is keeping it working (possible).

The color of your trans fluid has nothing to do with whether it's currently working correctly or not, regardless of what (nothing you can do about) turned it that color.

Again, even though I had the cylinders on power output stages wrong (I have a 40V with POs's built into coils), you still have misfires from both of them...and they rarely both fail simultaneously.
Cam (belt) timing off IS THE #1 cause of multiple misfires, that don't coincide with a single POS module...easy to check.
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Old 12-11-2011, 01:43 PM
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