I'm a new foru

I'm a new member, recently purchased an SRT6 coupe with 66k miles. Choice condition, but after a couple of days. developed a miss. Figuring it was best to get a clean start, replaced all coils, plugs, and ignition wires. Ran great - for one day, next time I started it, the miss was back. I had scheduled an oil change, trans service and AC check, so I asked the tech to run a diagnosis. He said #2 cyl was missing, the plug coated with oil. Suggested it was likely either a stuck or broken piston ring, or an intake valve valve stem seal. In either case it would require pulling the head and some $$$ repairs.
Has anyone encountered this? Any suggestions? I didn't hunt a long while to find a car that would send some mechanic's kids to college.
Love the car and really wish I could remedy this issue and start enjoying it.

 

Hello and welcome. A few questions to help clarify for myself and other members here. Where did you take the car, was it an independent mechanic that knows MB SLK-320/AMG-32 series Benz (the drivetrain for the N/A crossfire is almost 100% MBenz 2004(ish) SLK-320 (or if the SRT-6, the AMG-32 series MBenz). Is the car back home with you? Do you have the capability to 'self help' with various systems and/or replacing any parts? Also please include (if the car is back at 'home') if you pull the #2 plug yourself do you see if it is in fact currently doused with oil after the engine has been running for a few minutes. And finally, do you see/smell at the exhaust pipe, any odor or oily residue. I know it is a number of questions, but I ask your indulgence for all the posted questions in my query.


.

 

I have been here since 2009, I can honestly say I've not heard of someone dealing with this before. But oil fouled plugs are sure a sign of bad rings or valve guides.
It would seem that a compression test will tell you if the rings are bad, if they aren't, then it would likely be a valve guide (which would be less work and cheaper).


I must ask, was this a dealer purchase or private sale? If any our our members sold a car in that condition, I'd be surprised altho we did have a guy sell his car with serious issues, one time, a few years ago. I knew the guy was a creep and after that, we all knew it. Anyway, if it was a dealer sale, I think there are consumer protection laws you can fall back on. Very sorry this has happened.

 

OK, I showed your thread to Zach down in South Carolina, he had this to say (and he is way more of a mechanic than I am):




Get the car to someone competent, if you can't get the seller to make good on the problem he sold you.

 

Dear Ghost... I bought the car from a private party in MN (I'm in MA) had had the car shipped, so I don't believe there's any recourse. I don't think the guy intentionally skunked me, but... The mechanic I went to has a good rep w/ German cars, esp Porsches, but also BMW and MB. Yes one of the plugs was dripping oil. Yes, car is home now and I can pull the plugs for #2. Also, I haven't smelled oil or seen oily residue on the pipes. Is it even possible that a leaky breather or valve cover gasket could allow oil to get to the plugs? I torqued the plugs to 12 lb, so i don't see that happening, but...
In any case, thanks for your post.

 

Dear Pizza... valve stem seal sounds so much better, and yes, a compression test would show something, but would it differentiate between a bad ring and a valve stem seal.
Thanks !

 

On the Chrysler mechanic, I'm 78 but not senile or crazy. No way! Good independent German car shop, good references.

 

Were both plugs on #2 cylinder fouled ?

 

Yes, each cylinder has two plugs.

 

The question: were both plugs fouled ?

 

Yes. Bad rings cause low compression, as the cylinder leaks past the ring. Valve seals are not consequential to compression, as the valve is closed during compression anyway.

 

The plot thickens... and it ain't good. While researching the problem, the car sat for over a week. I started it to keep battery up, and WHOA! Firing on all 6, Took her for a spin (~ 50 miles) and it ran grrrreat; smooth at low speed, acceleration was fierce. Came home, started up next day and the miss was back. More specialists, offers at diagnostics: digital compression and also a leakdown.

Could the oil on #2 plugs dry off in a week, so that it would fire cleanly? Where is the oil coming from? Broken ring, valve guides, anywhere else?

Will the digital compression and leakdown tests tell me what's wrong? One shop estimates 6 hours to pull the tests. Another says ~ 20 hours to remove the head to see what's going on.
One says buy a used motor and get it installed - total approx $6000-7000 as opposed to a $15 k full rebuild.
People, I need help!! Ideas, experience, etc.
Can I pull the head myself? Some mechanical experience but years out of practice.
I'm getting confused and desperate.

 

20 hours to remove the head sounds a little ridiculous. Here's a link to use a hotter plug that may help with mis-firing :
https://www.google.com/search?q=will...t=gws-wiz-serp

 

Well, since you said PLUGS, I guess you answered my question if both plugs in that cylinder were fouled?

 

Are you sure it's oil? You may have a leaky injector.

Les

 

A simple compression test will tell you if you have bad rings or a cracked piston (doubtful, both of them).
I vote for a worn valve guide if you have good compresssion. That would cause oil to possibly get in there and such issues with M112s are common.
No need to tear the heads off, you can do a compression test yourself with a test kit, probably can rent the kit from a local store.

I'd not tear into the engine or change it until I KNOW what is going on. The miss can be unrelated to oil on a plug, there are a lot of things that can cause a miss to "come and go".

Oil does NOT evaporate.

 

I'm not certain. Would that make a difference?
Appreciate your question, though.

 

Thanks for the questions. No smell of oil that I've noticed, but I don't allow it to run long when it's missing. I can't see any oily residue on the tail pipes, but if I wipe inside the pipes, it's a bit more oily than just sooty. Hope that helps you to understand the problem.

I'm honestly getting pretty desperate. Can't be repeatedly forking over $500 for diagnosis. I know it's misfiring on #2.

 

I would clean the plugs and go for a drive to see if the oil on top of the piston burns off. Then remove the plugs and leave it for a while and then insert a bore sight in the plug hole to see if any the oil is dropping.
If not it is coming up from the piston.
For it to drop every time the engine would have to stop in roughly the same position every time unless one of the valves is pitted or is extremely loose in the guide bore.
My guess is oil leaking from a valve somehow.

 

Thanks, very thoughtful response; that makes a lot of sense.
I'll try it!
Uh, what's a bore-sight? Heard of them for guns, but auto?
Regards... Crow13