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Well my warranty ran out 11 days ago so now my car throws p0300. I did my own plugs 3 years ago but didn't do the insulators so I plan to inspect it all this weekend. Only things to change recently were today I was running errands and got closer to E than I normally go and the oil was changed about 500 miles ago.
And on my S65 The hole row 7-12 shut down. Found some oil in one plug hole. Cleaned it all out and replaced the plugs and installed a new coilpack. After that is run great for about 2 hours. I Went into a parkinglot and sat on idle for about 2 minutes and it shut down and after that I tried to start and it Went into limpmode and Check Engine is on again. Now when I reset it with star diagnose it missfires right away when I start it and goes back in limp and now it also sometimes give me a fault code on the Voltage converter. ECI. I will replace it this week to see if that fix the problem. Otherwise I am totally lost.
Last edited by Chris The Swede; Jun 21, 2015 at 10:24 AM.
For everyone's info I had misfires right after I changed the plugs. It ended up being that the gap was too wide and would misfire under boost. I tightened the gap up to the small end of the spec and have never had a misfire since. My mistake for not checking the gap prior to the initial install.
I believe the factory spark plug gap is .7mm or about 0.027 inches. The plugs that I was using out of the box were a bit over .040 inch and would not fire across the gap at high boost. Make sure to check before installation.
For reference I was using the Autolite iridiums.
Last edited by Flight Test; Jun 23, 2015 at 07:51 PM.
Reason: Mislabeled .040 as mm instead of inches.
Has anyone tried taking the top off of the coil pack and testing out what fried? I know you can get MOSFETs for reasonable money and solder them in, but I'm not sure if that is what gets cooked in these things to make them randomly die off.
Has anyone tried taking the top off of the coil pack and testing out what fried? I know you can get MOSFETs for reasonable money and solder them in, but I'm not sure if that is what gets cooked in these things to make them randomly die off.
Howard reported that in his maintenance thread. He fixed his coil pack and I believe its still running strong.
Yea,I too have a problem with my Left Coil pack.
Miss fires on all six,codes are P0300(random) and 307-312.
It runs fine on a cold start for about two minutes and that's that, check engine light comes on and miss fire badly. I have to admit that besides regular oil changes and top up with oil in between I haven't do anything to maintain it.
Thanks to the Forum here with another DIY instruction to remove and replace the coil pack, I was able to pull the pack out with minimum effort.
I attached some Pic below,
Coil pack is nice and clean by only looking at it, No arcing/burn marks/separation on the tube. too bad there is noway to test it out?
Red insulate boots are kind dry but not cracking.
Spark plugs are something else, I bet you guys have never seen anything this bad.
I did notice that I need a Valve cove gasket replacement as well,you'll see it in the photo, my question is do you think it's because the Valve cover leaking and oil drips down then slowly ruined the plugs and coil pack? but all the Red boots are clean without any trace of oil. Some Plugs threads are covered with oil, I don't know if it's just the oil just sitting/collected outside the plug and when I unscrew them and oil got on them?
Last edited by fisherman123; Jun 30, 2015 at 03:25 PM.
Thanks Biker! Sorry,My bad, I forgot to mention I already swapped out mine with a known good one from my Indy and that didn't help,at this point he thinks it's the pack and of course he doesn't have an extra pack for me to play with.
Last edited by fisherman123; Jun 30, 2015 at 04:51 PM.
Had misfire, scanned the code and got Cylinder 3 and 4 misfiring. Turned off the car, turned it back on and all was normal, this was 2 weeks ago. Drove 100 miles in two weeks, today, drove from home to the gym, hit the weights, came back out and started the car and had a misfire, same cylinders, 3 and 4. Turned off the car, turned back on and back to normal.
See previous posts above ......Could also be ignition transformer module that sits on top of engine - $1500. It also sounds like coil is shot. Are your coils upgraded to new part number? Once I changed the ignition transformer module, all plugs and both coils my problem was solved for 2 years then I replaced them all again then sold the car and gave up on the V-12.....this is an update from post above...was disappointed to sell the car...got 40k at Car max when MB would only give me 30k several years ago......drove it a total of 5 years - 30k miles and lost 5k a year in depreciation and probably another 5k in repairs...expensive car to maintain - also motor mounts were shot which required engine out and I gave up - Car needed about 12k in out of warranty repairs to keep it on the road after coil debacles.....
At 58k miles sold it - differential discs shot, another ABC struts failing and ABC hydraulic lines having to be replaced because pressure constantly exceeded the specs MB designed in weak lines....needless to say I learned lots about AMG - will not buy another - went Porsche GT Cars....
See previous posts above ......Could also be ignition transformer module that sits on top of engine - $1500. It also sounds like coil is shot. Are your coils upgraded to new part number? Once I changed the ignition transformer module, all plugs and both coils my problem was solved for 2 years then I replaced them all again then sold the car and gave up on the V-12.....this is an update from post above...was disappointed to sell the car...got 40k at Car max when MB would only give me 30k several years ago......drove it a total of 5 years - 30k miles and lost 5k a year in depreciation and probably another 5k in repairs...expensive car to maintain - also motor mounts were shot which required engine out and I gave up - Car needed about 12k in out of warranty repairs to keep it on the road after coil debacles.....
At 58k miles sold it - differential discs shot, another ABC struts failing and ABC hydraulic lines having to be replaced because pressure constantly exceeded the specs MB designed in weak lines....needless to say I learned lots about AMG - will not buy another - went Porsche GT Cars....
$1500 is a lot to shell out, even 1200 for coilpacks is steel, but I guess i'm going to have to do that. Most of the time, misfiring are caused by bad coils on any other "normal" cars that has an individual coil firing the plug...this design is terrible, most coils cost about 50-70 on normal cars. This car has 6 on each side, most MB should charge is $600.
I have had 5 V12s now and NEVER again. Trouble with ALL of them!! They use the same **** since like 1998.And never improves them..You have echange services for them as well. Like 360 each..
I have had 5 V12s now and NEVER again. Trouble with ALL of them!! They use the same **** since like 1998.And never improves them..You have echange services for them as well. Like 360 each..
Fool me once...lol
5 times? Oh well, live and learn right, this is my first and last V12 as well. The power delivery is incredible but the maintenance and how tight everything is crammed into the car, is discouraging even for a mechanic like me.
Unfortunately I'm not able to report the same with regard to the hard starting and multiple misfires after a 15-20 minute heat soak with the engine off. Although it does not seem to occur as frequently as it did prior to replacing the CPS, it still nevertheless gives me trouble from time-to-time. While it's possible the CPS heat soaks above its rated temperature range (-40F to +300F) I suspect that the issue actually lies somewhere else - perhaps something within the ignition transformer overheating.
There definitely appears to be a relatively narrow window where the heat soak builds up enough to cause hard starting. If I shut the car off for only 5-10 minutes, it tends to restart normally. If I allow the car to sit for 45 minutes or more, it seems to cool off enough to start fine. Somewhere between 15 - 30 minutes seems to cause the most repeatable issue.
I plan to install some temporary ducting to the ignition transformer at some point just to verify whether or not increased airflow after engine shutdown will eliminate the issue. If so I'll try to better insulate the transformer from engine heat, and if that doesn't solve the issue, ultimately I may need to replace it.
Despite the age of this thread, I always hate it when I find information like this online with no definitive closure, so I didn't want to be guilty of doing the same to others...
While troubleshooting a fuel delivery issue with this same car a couple of years ago I determined that although my digital multi-meter showed that my electric fuel pump was receiving +12v, the pump itself would not operate. Thinking that I had correctly diagnosed the issue as a defective fuel pump, I replaced it with a new OEM part (001 470 87 94). Imagine my confusion when I found that the replacement fuel pump wouldn’t operate either…
To make a really long story somewhat short, I ultimately discovered that this system has a fuel pressure sensor (003 542 48 18) located under the driver’s side exhaust heat shield, and its signal is sent to the fuel pump via the fuel pump controller as a pulse width modulated voltage. This sensor had apparently failed internally, and even though the DMM was showing +12v, in reality it was only sending the fuel pump a small blip of current at perhaps a 3-5% duty cycle. The DMM was clipping the signal and making it appear to me that it was measuring a constant +12v, when in fact the circuit was off >95% of the time.
As expected, replacing the defective sensor completely resolved the fuel delivery issue. What I didn’t expect to find was that since replacing the sensor, I’ve not experience even one recurrence of the heat soak-related hard starting issue.
I suspect that the sensor had probably begun to fail quite some time ago, and once parked it would heat soak from the exhaust, dropping it's signal to this very low duty cycle. As it cooled off, the modulated voltage duty cycle would increase to the point that the electric fuel pump would begin operating again, and the engine would start.
I’m really happy to have been able to discover this issue, as I could have easily wasted a ton of money replacing the ignition transformer, coil packs, and a host of other costly items.
Finally, with regard to the random misfires during WOT, it appears that these are most likely due to an issue with the throttle position sensor located within the accelerator pedal. After clearing all the active DTC codes, I was able to trip the MIL/CEL light and record a P0123 (Throttle Position Sensor/Switch A Circuit High Input) DTC while parked in the garage with the engine off/ignition in the number II position, by simply pressing the kick-down switch repeatedly with my finger.
Having essentially concluded that the random misfires were indeed the result of a defective TPS within the accelerator pedal assembly, I ultimately felt justified to spend the $200 for a new one (A 230 300 01 04). Since replacing this component, I’m pleased to report that I've not experienced a single WOT misfire in nearly two years!
I appreciate everyone’s suggestions, and I hope that the information in this thread helps someone else in the future.
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