2005.5 4.2l errors: Multiple random misfires....

B6/7 S4/RS4
#1

Hello all,

This is my first post on this particular forum. I purchased my 2005.5 S4 a little over a year ago. Yesterday I was on the highway going about 75mph when I started to feel a small shudder (as if the road had small bumps) and then I noticed the check engine light was on. I pulled over immediately, and at idle the car was missing quite obviously. I turned the car off and tried to restart it and it had a hard time starting and was missing so bad it couldn’t stay above 200 rpm. I shut the car off, and plugged my scanned in getting codes for random multiple misfires, misfire cylinder 4, misfire cylinder 6, and misfire cylinder 8. I called a tow truck and now the car is in my garage.

I am planning on checking compression in the misfiring cylinders tonight. Does anyone else have any advice? Any indication of what it may be? I’ve read anything from the MAF to timing chain guides/tensioners etc… I’m hoping it’s not the timing chain but have a feeling it may be.

Thanks for any input.

#2

Here is the good news. Your on the right forum. Welcome

Right to the issue.

Was there any other codes. Any knocking. When you started the car over the past few months did you get the knocking on start up. How many miles are on the car.

There is a good chance that its the plugs and coil packs. The coil packs and plugs tend to go bad out of no where at times. Generally if you have broken guides youll see camshaft performance spec adjustment codes. You wont always get codes but its very common.

Here is the thing. The guides will go bad and the guides will break. Its not if but when. So that is something you need to keep in mind.

if you can give some information back about the questions I gave that will help us help you. Also if you did have a issue with the guides breaking a comp test will help give you an idea

#3

In addition to what Justin said. Make sure to do a compression test on all eight cylinders.

That will give us more info. Like if you have an overly retarded set of cams then the compression will be low on that whole bank. Usually the lower left guide always breaks and it allows the driver’s side camshafts to back off from where they should be. At least that is the way that every BHF 4.2 has been that I have cracked up.

#4

For refrence here is the list for compression test results for several others on the site.

It would be helpful good or bad if you posted your results

http://audirevolution.net/forum/index.php?topic=727.0

#5

Thank you for the response!! The car has just over 131k on it. There hasn’t been knocking on start up, but there has been a bit of a rattle. I’d say this lasts for about 1-2 seconds, and doesn’t always occur, usually just when it’s cold. There weren’t any other codes.

We’ve definitely got the chain on our minds and if we decide to keep the car for another 3-5 years we will be doing the intermediate service kit from JHM. :smiley:

#6

I will definitely check compression in all 8 holes.

#7

Excellent, thank you! Will do.

This seems like a great forum, I’m on several others that aren’t as welcoming. This is quite refreshing. 8)

#8

This is one of the most recomended forums. Most of the tech savy guys left other forums to come here. Its much more car and car guy friendly. Were all here to help all we ask is if you got some good help here pass on the AUDIREVOLUTION if you see a good guy struggling on other forums. With such strong guys moving from other forums this site now gets blocked on other sites. Kinda seems like other sites dont want to let other members know about the better options when it come to help for there cars.

If you got any questions feel free to keep em comming. and Welcome again

#9

Well…bad news guys. Cylinder 8 has no compression because there’s a hole in the piston. :’( Looks like this car will be sitting for a year or so until we decide to either have some machine work done and try to salvage this engine or try to find a used engine. The car’s only worth 10k at best so I don’t really want to throw more money than needed at it.

I guess the good news, if you can call it that, is that once we have the engine out (either this one or the “new” one we buy) we can do the timing chain service on it.

Looks like we will be keeping this car forever now. Might as well not dump a few thousand into it just for someone else to enjoy. Sigh. :-\

#10

Oh, just to add, the spark plug broke off in which is what caused the hole in the piston. The rest of the cylinders have good compression, which I guess is a good thing.

Does anyone know what would cause that? Timing chain related?

Thanks

#11

Ouch, feeling for you. Other, far more knowledgeable, forum members will hopefully chime in, all I can really offer is sympathy, but plenty of that. :’(

#12

Do you have any pictures of the spark plug? Seems like a strange failure mode! Wonder if the plug was defective. Or if it was caused by something else; to much fuel in the cylinder causing combustion overpressure (if that’s even possible; maybe if a knock sensor is toast?), ignition/electrical surge through the plug itself? I don’t know, just tossing some layman theories out there. How/where exactly is it busted?

#13

Also, bummer news. With all the things that these motors are known for you just drop a plug and that’s all she wrote. Sorry to hear, hopefully you can get her fixed!

#14

Here is the plug

http://i258.photobucket.com/albums/hh267/m_shuler/spark%20plug_zpshfqhkpcx.jpg

We aren’t sure if it was running lean and that caused detonation or what. All of the other cylinders have good compression and the plugs looked fine, so I guess that’s good?

I’m afraid to see what the valves and seats look like after seeing the chewed up piston. I couldn’t even see the entire piston, I could see enough just looking down into the cylinder through the spark plug hole.

#15

It doesn’t seem to be melted, but it could be. I don’t know if the plug broke and caused the hole in the piston or if the piston chunk beat the spark plug up.

We will know more once we tear it down, but like I mentioned above, we are probably going to let the car sit for the next year while we get our house in order to sell and move etc.

#16

You would have to pull the piston like you said. It looks like its collision related more so then plug related. Getting the entire bottom of the plug to fail like that would have to be quite a feet.

The good news is there is still development for these cars and still parts coming out. JHM is still putting out parts and now your seeing a few guys go stage 1+. I dont know where the built motor program is but that might be something to look into as well.

#17

Definitely! I guess the upside is that it will be fun tearing the engine down, and deciding how we want to rebuild it (whether stock or not so stock). It’s just an expensive shelf in the garage for the time being. :smiley:

#18

When your ready we are all here to help if you need it.