woowoo

64K miles. Started running rough at idle. took it to my indy MB shop and they came back and said codes indicate: cyl. 1-b, 2-a, 3-a&b, 4-a, 6-a&b, all showing misfires, with 6 being the worst. they said I need new plugs and wires, but coils are also possible. I said lets find out 1st so they swapped coil on cyl. 5 & 6, said it made no difference 6-a&b still misfiring. They wanted $942 to replace plugs and wires. I said button it up and I'll come get it. I paid the $140 for 1.5 hours of shop time. Bought 12 new bosch plat2 for $60 and replaced them all last night. 1st time doing it to a MB, took about 3 hours thanks to reviewing the many great DIYs here, and I took my time. btw, I made my own 17mm offset wrench from a cheap offset box wrench by cutting out the end and doing a bit of grinding to make it thinner. took about 10 minutes and worked great. The plugs looked pretty much the same across all 12, some what dirty but not horrible. All the wires,coils ans connectors looked clean and OK.

Now it is still missing, checked codes and now it is showing misfires on cyl. 1, 2 & 6. this was with an ODC not the star at the shop so I did not get any read on a or b per cyl.

So now what? with the swap of the #5 & 6 coil at the shop and no change to cly. 6 missing. Unless I am missing something, 100% possible, I don't see how wires or coils can be the issue. Now that all new plugs are in place what else can be going on? I am sure that all the wire connectors to the plugs are tight (I used dielectirc grease on all and they went on easily with a good click and I rechecked and they are all tight). Plus are also torqued to 20ft.lbs.

BTW, I am also now showing a P0100 MAF sensor error and a P0110 IAT sensor error. These are new as they did not show up from the shop. So I am really confused. Any thoughts o ideas are most appreciated.
thx

shuor

My next step would be to replace the wires :o

ohlord

the wires alone,they don't wear out,if not abused and you did not abuse them.
Can you borrow a good maf from a member that lives near by?maf and iat are intergrated.You have misfires on both banks and the maf going bad would cause that.You could try cleaning,with crc brand maf cleaner but I think it is shot and the proof would be swap in another known good 320 maf.

You will have a hard time tracking down misses when you install the wrong plugs.
these m112 and m113 series engines hate multi tip plugs and that is why oem and oe dictate single side electrode plugs like the 7422 bosch or the ngk 7090.
your first clue it was not the plugs is they all don't fail at the same time and are good for 100k in a properly maintained engine.

So in this order
anybody check for intake leaks or when they were screwing around with the plugs that they made sure the maf harness was plugged in firmly?
swap maf
change fuel filter
put in the correct oe plugs
leave the wires alone
never go to that indie again,they are screwing people
ohlord

ohlord

don't list where you are located so if a member lives near by they can loan you a good maf.Autohausz.com has great prices and free delivery over 50 bucks.
ohlord

woowoo

ohlord, thx for the tips. I am live in austin, tx, but raised in SEA and UW grad, went there when we had a football team (Don James era) so you can make a good guess at my age.

I verifed that the MAF was plugged in and secure. No one checked for intake leaks. How would I do that?

Anyway, I think I will try cleaning the MAF today, it is easy, quick and inexpensive so worth a shot, not out much if nothing changes. If that fails I will just replace, probably just the insert as i don't see any reason to replace the housing, unless there is a reason to? I am also thinking the fuel filter is worth replacing anyway so I will do that as well.

Bummed about the plugs! Why would Bosch say that these plugs are good for this vehicle? $60 and 3 hours wasted on the wrong plugs, crapola!

Once we solve this problem I am going back to the indy shop owner and tell him why he has lost my business.

Thanks again for all you help.

Hirnbeiss

This sounds like a perfect case for Dr. House & gang

woowoo

I drove to the parts store to buy MAF cleaner and checked codes while I was there, now I only had code P0306 for cyl. 6 misfire, all other previous codes were clear. Bought the MAF cleaner anyway and cleaned the MAF when I got home. It looked clean to start but its real clean now. I also decide to try swithcing the coils on 5 & 6, back to original locations, assuming the shop did this test as previously posted. Drove the few miles back to the parts store and checked codes again. It now shows cyl. 5 and cyl. 6 misfires. I double checked the coil and plug connections when I did the swap and am sure everything is getting good connections. At least I no longer have MAF or IAT errors but the misfires continue. 2 steps forward one step back.

I am going to let it cool off a bit then reverify all coil and plug connections on 5 & 6. I think I will switch the coils back again and see what that yields. Maybe the #6 coil is bad?

Anyway, I am getting pretty proficient with plugs, wires, caps and coils.

I am also going to buy a OBD II so I can check and clear codes myself.

Any other ideas, thoughts or things to try?
thx

ohlord

on sale 55 bucks,great little unit.
http://www.harborfreight.com/cpi/cta..._stores.taf#TX
#94169
swap coils or swap wires and also check with a shop stethoscope(a few bucks at hb tools)the sound of the injectors on 5 and 6 ,might be time for a good seafoam injector cleaning.1 can in the gas tank when near empty and fill 1/2 way drive till near empty and fill as normal.You could have a plugged injector or dirt in the fuel rail.

woowoo

I did switch the coils & wires from cly. 5 back to cyl. 6 last night, still running poorly at idle. Checked the codes and now showing cly. 2, 5 & 6 misfires. I did not touch the the #2 side of the engine when I swaped the #5 & #6 coils. I am now thinking there is not and never was a problem with the electircal (plugs, wires, coils) but that this is a fuel problem. I appear to be just getting random cyl. misfires, except cyl. 6 is consistently reporting them.

I am about 1/2 way through a tank of Chevron supreme with an extra bottle of techron in it. I bought SeaFoam and will use that following ohlord's plan.

I am certainly glad I did not give my (ex) indy shop $942 for new plugs and wires! I'd be out a grand and I think still having misfires.

I'll update when I know more, as always any ideas or suggestions are most appreciated.

thanks for all your help so far!

Hirnbeiss

Just thinking out loud:

Wouldn't a faulty Crank Pos Sensor produce similar symptoms? It has my vote for most liekly candidate right now.

MAF is possible, but I would expect other codes as well.

Fuel filter possible, but I would think it would happen more with more throttle, and less at idle.

Clogged / broken cats?

koskesh

I know for a fact the Bosch Plat2 spark plugs will cause the random misfire code in the M104, I know you have a different engine but it's worth mentioning here. You might want to try the Bosch copper spark plugs before spending any major money on a coil or something.
Apparently the plat2 plugs don't work too well for these engines. I got the random misfire code after putting those in. Put conventional copper plugs in and problem gone.
Make sure they are gapped correctly, I can't remember off the top of my head but if you do a search that information is on this forum.

ohlord

is an m112 so it needs the platinum plugs,just not the multi tip ones.
They come out of the box gapped at the proper .039 or apprx 1mm.
m104 you are quite correct oe plugs are also called for and that engine hates anything but the recommended plug also.Don't know how many times I can count the people in the amg forums that change to mag wires or snake oil multi tips and then have misfires and go wtf
ohlord

woowoo

to do any more experiments. I will provide an update shortly, as soon as I can spend some more time on it. I am also waiting for scanner and some parts on order.

Thanks again for all the tips and suggestions and I will post an update on what happens.

woowoo

Hi all,
It was spark plug wires. Once I got my scanner I verified misfires on cyl. 6. I swapped just the wires between 5 & 6, the misfire moved to cyl. 5. Plus it was both wires that were bad. The car ran the same when I totally unplugged both wires. So both cyl 6 wires went bad. That seems pretty strange. Anyway, I was also seeing occasional random misfires on other cyliders. Installed all new wires (about an hour job) to go with the plugs I had installed ealier and everything works great. car is running very well.

I strikes me as strange the way this failure came about. The car just started running poorly, misifres on cyl 6 and occansional other cylinders with 64K miles. Plus the shop saying misfires on multiple cylinders seems weird that wires would all start failing around the same time. Oh well, live and learn

Thanks again for your counsel and ideas