I've been troubleshooting a recent gremlin and I'm hoping you all have the answer. I've been doing a lot of searching on here and most threads that sound similar have no conclusion. She throws CEL's for misfiring on 1,3 and 4 today, yesterday it was 1,3,4 and 7, plus P0300, multiple/random misfires. She starts just fine, hot or cold, idle is smooth for about 5 seconds, then it'll stumble a little, nothing horrible. I can make the misfires and CEL pop in if I hold the idle right at 1000-1200 rpm, at that rpm, it seems(my app won't read the AFR) to get really rich, with steady pressure on the gas pedal, she'll drop back down to about 800 or so, then back up to 1200-1500. I've pulled o2 sensors that are relatively new, I've moved them from side to side to see if anything in my fuel trims will move, no change. I pulled the air intakes and air boxes, looking for vacuum leaks, can't find anything disconnected. I can get this to happen every time I drive now. I'd clear the code and she'd be fine. It has no problems running at WOT. Could the crank sensor cause this? She's got 133k on the clock, spark plugs are fairly new. The plug wires are original and I do have new oem ones on the way, but it doesn't seem like that's the issue. Long tube headers, no primary cats, stock secondary cats are in place. I've disconnected the battery, pulled the ecu connections and reseated, no change.

I took a quick log of the fuel trims(I really don't know what I'm looking at here). I'll try and paste it below, hopefully it works. You can see when the rpm goes up the trims get especially wild. I would assume that both should be close to each other but like I said, I really don't know. Swapping the 1st o2 sensors from one side to another did not change which side has higher #'s. The secondary o2 sensors are turned off in the tune.

Idle isn't high like I've seen when I had a little vac leak in the past.

Sorry for the random mix of information, just putting it down as I think about it.

Ok, pasting it didn't work and I couldn't upload the .csv, tried attaching it in a text file. I may be way off base by looking here, just don't know what's next.

Any thoughts? Thanks for any info!

EDIT: new oem fuel pumps and delivery unit as well....

Edit again, just swapped #1&3 coil packs with 5&6, no change.... she's parked for the evening.

 

Can you post your LTFT

 

yes sir... maybe

I took a log just sitting in the garage, made CEL come on again, misfire codes on cylinders 1,2,3&4 codes this time, +p0300.

Long trim just showed goose eggs, does it need more time to gather this data? If so, I'll do it tomorrow. Attached the file though, the first half idling and me trying to hold 1000-1200 rpm, the second log is just sitting idling.

Thank you for looking Shardul, I have a feeling I'll be buying a STAR package from you soon.

 

LTFT should be + - 5%

 

I feel your pain, Most of us been there.
You started off by saying misfire on 1,3,4 and no more misfire on 7 which is on another bank- what did you do to stop #7 from misfiring.
The crank sensor just measures the speed of the crankshaft and reports that info to ECM if the Crank position sensor is completely bad your car will not start, when its failing your car starts and shut down until one day it doesn't start, I just changed mine.
You also said you changed coils number 1 and 3 with 5 and 6 and no change.
What about coil number 4? you made no mention of a swap. On a random misfire it could be just one cylinder misfiring and you get a false reading on another cyl so change all (three)cylinders misfiring with three good coils that are not misfiring.
Check wiring input to coils to see you have 12 volts.
Check to see if spark is going from coil to spark plug.
If all fails do a compression test on each cylinder that is misfiring.
Try to put up info on fuel trims, Is it in Closed loop or Open Loop?

Good Luck!

 

You state the car has original spark plug wires at 133,000 miles and 8 years, probably at least one set of plugs. Any chance you are running a cold plug, the combination, weak coil or coils, plug wires possibly stretched when taken off could be a source of your trouble. Pull the plugs to verify colour, gap, using a known good coil try it on one of the misfiring cyls, reset cel. See if it returns with the same cel or changes to another cyl.
Could it be related to your tune or possible injector or injectors dirty?

 

Check the connection to the coil packs. Overtime those plastic clips get old and brittle and break. Double check to make sure the connection to the coils packs are sure and tight.

 

Good info guys, thank you. I'll try some more recommendations and report back, starting to suspect my o2 sensors, even though fairly new, may have been contaminated. I had them in and out a lot while wrestling a little exhaust leak at the slip fit collectors where i ended up using a little high temp rtv to assist the seal. I've been reading that those sensors are very sensitive to contamination by rtv. She's a weekend warrior to me, I'll have some new parts in the mail next week to try out and let you know.

Edit: Just checked and the rtv I used says it's sensor safe. That'd be too easy I guess!

 

I agree with check spark and fuel pump, if you do that and all good then compression test

 

Same thing has happened to me before when the primary O2 sensors became really lazy/fouled. LTFT's skyrocket positively indicating the ECU wants to pull fuel out, like the car doesn't know how to fuel itself so dumps in the fuel to be safe? Anyway, I swapped out primary O2 sensors and everything returned to normal.

I've had all the mods listed in my sig for the last couple of years and the only codes I get are for primary O2 sensors when they start to go bad, which on the Bosch OEM sensors has been about once a year, likely due to rich part throttle maps in the tune.

 

Hey guys I am having a similar issue with the c63 which the same engine to the e63. I am in the process of trying to change out the primary o2 sensor but have no idea how to get a wrench in there, any advice?

, https://mbworld.org/forums/c63-amg-w...ight-help.html

 

Are o2 sensors sensitive to dropping? I bought two new ones(Bosch), and when they arrived today, the box was smashed and the two boxes for the sensors had obviuosly been smashed too. There is no apparent physical damage but how about the internals? I don't want to put them in if they are suspect. I did get a very good deal on them from Amazon at $75/each. Too good to be true? Maybe the boxes were smashed before they shipped, who knows! So I have two o2 sensors, new plug wires and a crank position sensor hopefully going in by this weekend if I find the time. I suspected the o2 sensors even though they're not that old and ordered them Sunday, also jmb614's post makes sense to me with a safely rich running tune, we'll see soon hopefully!

Yooker, I have no idea where they are stock, they're very easy to get to with long tube headers! :-)

Thanks again guys!

 

New o2 sensors did the trick, night and day difference. Here's the link if anyone needs them in the future.


At half the price I could find anywhere else. I'll be putting the other parts on this weekend just because it's time.

Thanks for the guidance fellas!

 

How long have you driven with the new O2 sensors ? I had the same basic set of errors (but car runs fine) - P0300, P0140, P0160, P0303, P0304, P0305, P0307, & P0456....

I cleared the codes and the CEL has not yet come back on (I'm sure it is just a matter of time), but the car runs fine. I have no stumble, no real misfire, etc.

 

MY c63amg is stoke only i change to K&N filter on it and was 55k. I have engine light on so i changed all spark plugs and still light on .The old plugs look pretty clean so We did diagnostic on it and show 18 codes. from first to last code are p0301,305,302,306,300,303,301,305,302,306,300,304, 303,300,301,305,302 and 303 and test the batter to show that bit low. the car run fine but for example i drive for 30min that turn off for 10min and start then i can notice ruff running till shut of and re star it then run nine, Can so one help me and tell what cloud be problem.

 

My error codes thrown P300,307,308. Pulled plugs and one plugs electrode was broken. Pulled SC and found one of the knock sensor wires frayed to the bare wire... I suspect it was shorting against the body causing the issue ... Especially since my misfire occurs after engine been run a bit ...

Need to figure out how damaged the wire is and re-re everything ... Might check compression before I put everything back to be sure.

Also had one step colder plugs and going back to oems.... Checked cylinders with borescope and saw nothing untoward....