mb1

hey guys.. need a little help over here.. i recently bought an sl55 and so far twice my cylinder #8 misfired. I have done and/or checked the following:

spark plugs. gaped at 0.031 per manual for sl55
switched coils just in case with another cylinder
checked compression and same as other cylinders 150psi
oxygen sensor Bank 1.. passanger side (this one caused random misfire on that side and once replaced, no more issues. )

what i have noticed is that it does smoke up on start up. reading other posts it seems to be normal or start of valve seals going bad.. so yesterday the car was running just fine and then started misfiring.. i drove it for 4 miles to get back home while it was misfiring and pulled into the garage. i shut the car off, checked the code and yes #8 mifired. i cleared the codes, started the car and no problems.. runs perfect. the 2 times it has happened i was driving the car in the city at average speed. at this point, i'm clueless
would oil in the cylinders from seeping valve rings cause the misfire by any chance? or any other suggestions would be greatly appreciated.

thanks guys

overZealous1

crank position sensor can do it also.

Hulk

Check your injectors as well

mb1

thanks.. did you mean Cam sensor?? my understanding is if the crank sensor is bad, the engine fails to turn over or start.. cam may cause a misfire... i was just confused as it didn't do it all the time just random BUT on the same cylinder.. will keep posted if that works.. any other suggestions are welcome..

thanks for the help

mb1

i thought about that, but would an injector cause this? what's weird is that i put on 30 miles since the car has done it, just random driving in town.. i have noticed it that it did it when i drove the car and let it running while running inside the store real quick.. 5-10 min at most.. that was 1 occasion.. the 2nd one was just while driving after 20-30 minutes.. it's just weird.. i do wonder if the cam sensor starts failing..

overZealous1

ya, unfortunatly there is just so many things that are part of that circuit all the way down to internal individual circuits in the ecu. the comp giving you back a #8 misfire doesn't narrow it down much at all either. it does lend more towards a mechanical or hard parts issue, but the ecu does not always catch and toss up the correct code for a sensor on it's way out or giving partially faulty outputs.

alx

Run a bottle or two of chevron techron.

Also check if your air filters are dirty.

mb1

I will try with Cam sensor first and see if that takes care of it.. i already ran some cleaner 2 tanks ago, i just can't recall if i did it before changing the plugs or after.. my thought is that i did it after changing the plugs.. I will check if the fuel injector is spraying correct.. just looking at it, does this mean removing the supercharger to get to it?

mb1

did both of those and still.. waiting to try the cam sensor and to check the fuel injector..

thanks for the input

cal1

Plug wires maybe. I had a set of EvoSport plug wires get brittle and throw misfire codes. Went back to stock wires. I have also heard the plug wire boot can get damaged if not careful removing them. If I am not mistaken their is a special tool that MB uses to remove them.

mb1

UPDATE:. well changed the Cam sensor and nothing still the misfire is happening.. cylinder is stil at 150psi but i am burning through oil more then i should have. It's almost 1 quart for every 200 miles..

Todays to do is to remove the supercharger, inspect it and the gasket, clean the fuel injectors.. if this doesn't fix it, then i have no idea what it is.. the wires seem ok as the car doesn't do it until it's been driven for a while.. 10-15 miles or so... stay tunned

overZealous1

good luck man. i hate these types of problems.

cal1

that's a lot of oil. I put maybe 5,000 miles a year on my car and change the oil every fall before tucking it in for the winter. I burn maybe a quart. The car has 90k on it.

mb1

according to MB specs, the car should burn 1qt per 1000.. which that is still a lot.. i was gonna do a leak test but the local shop here said that this car it will be $300 to do so and to replace the valve guide rings, it's $900 total.. since their computer shows it takes 3.5 hrs to remove spark plugs.. I was like, no way, it's a 30 min job.. i can do it with my eyes closed.. but they wouldn't budge.. so, i will have to perform my own leak test and see where it goes from there as well.. i'm pretty confident it's the valve guides as it is doing it on all cylinders.. at least according to my spark plugs

just can't wait to go home and start removing the supercharger..

also i did notice that i may be using up coolant a bit.. i hope it's the supercharger gasket or something easy..

mb1

well switched out the fuel injector with another one to see if that's the case.. sprayed it down just to make sure.. and i believe it's still not doing it.. i will have to drive it tomorrow to find out for sure as it didn't misfire.

when i took off the intake, i looked down in the valves and all the valves had some oil on them but #8... that one looked really dry and almost like antifreeze was on it.. any thoughts or suggestions?

i didn't take off the supercharger yet to check the intake, but i'm getting a feeling that the head may be cracked.

thoughts?

thanks

alx

If it looks really dry it is because it is getting to really high temps that burn off everything. This is usually indication of lean running conditions.

I believe your #8 has a clogged injector.

During the initial engine warm up additional fuel is injected which masks your lean condition. As engine warms up fuel is dialed back and your lean condition (and misfire) shows up.

The oil consumption is unrelated.

Given thr information you provided, that is my theory right now

Also, it is possible that due to your heavy oil leak down your #8 plugs are getting wet causing the misfire.

coldwell

I know that you already did this ,but remove and switch keeping them all together from #8 , coil , wires and plugs.put them on other side of engine. also when it happens again , let in run for a second .pull the code .make sure were on #8.then check to see if plugs on #8 are a little black or clean from no fuel.
As I dont have my 06 in front of me at this point.check for any vacume hoses that come from that cylinder.
let us know what you find
good luck.

mb1

This is what I have done:

swamped the plugs with #5 cylinder, same with coils same with fuel injector and this morning i started it again and getting cylinder #8 misfire.. my initial thought was that maybe the fuel injector was bad.. It could be a possbility that is running lean, but what i don't understand is, this morning i started it up cold and it blew smoke. oil smoke and was misfiring instanteniously. i drove it for 2 miles, shut it off at the light and turned it back on.. no problems at all. I am using up coolant and yet to find out where it's going. My original belief was that my valve guides are bad and leaking oil into the cylinder.. some more some less causing the cylinder #8 to misfire.. when i did the compression test, it showed 150 on #8.. so i'm pretty lost at this point.
i'm thinking of buying a leak down tool and testing it, but that will only tell me so much

mb1

well, it rules out the fuel injector.. swamped it with #5 and still misfire on #8.. only way to find out if the oil is the issue would be to dig into the engine and replace the valve guides.

coldwell

You stated your using up coolant , is it possible you have a small coolant leak at that cylinder??

mb1

most likely.. will see with leak down test i guess.. not sure of other ways of doing it

amok55amg

Worth to look at this since my car was not running even on all cylinders from time to time ....... but you don't have this error code .....

https://mbworld.org/forums/sl55-amg-...ow-should.html

GermanCars

I have seen some really ugly pictures from a C32 with symptoms you describe-engine misfire plus coolant loss. Turns out the intercooler inside the supercharge failed and was allowing engine coolant into one cylinder. Apparently the burned coolant is really hard on aluminum, in this case damaging the cylinder, piston, and cylinder head. My suggestion is to stop driving the car until you make sure you are not hurting something.

mb1

ok this is what happend:

my head gasket was bad and so were my valve seals and guides, causing more oil and coolant to get into the engine therefore causing misfire. the worst was on cylinder #8.

the cost and amount of work required to replace it:

in order to get the heads off, the engine had to come out of the car. Now this is per the mechanic.
I ordered all the gaskets, valve guides and seals from ebay and a company from Tennessee.. the total cost with shipping was $800, which was really good compared to located MB dealership of $2200.
The machine shop was right about $400.

THE LABOR. now if this was any other workshop, it would have cost me an arm and a leg. This guy quoted me originally $1000 to do the work; however, since it took him a lot longer then 1 week as quoted, he cut his price in half.. so $500.. the total job ended up costing me about $1800, which i'm extremely satisfied. just thought i'd let you guys know in case you run into something like this.

just a tip. The mechanic says he tried without taking the engine out and it was almost impossible due to timing cover not being able to remove it with engine in. he did say that this engine was one of the easier ones to remove out of the car.

thanks for all your input.

amok55amg

Good to hear you have it all fixed ... and for good money too

How did you know which kind of valve guides and seals to use? just new original or repairs? ..... also - according to STAR it's not necessary to take the engine out to do this but on the other hand it's much easier to work with ..... timing cover should not be removed ......
Did you have your heads machined? .... do you have any pics. of the heads before and after? ... and hopefully your mechanic also used Loctite with the new gasket?