Long story short:
In December I replaced all my spark plugs and my left (7-12) coil pack because the entire bank failed.
Last night I installed a new right coil pack because I was getting cyl 2 misfire.
Today, things were running great until this afternoon when it had difficulty starting (like it took a couple seconds longer to start than the usual immediate startup). Didn't think anything of it aside from "odd, it hasn't done that before".
Then driving back to the office, I gunned it through a yellow light (trying to clear the intersection before the red light cam fired), I heard a soft "pop" (backfire?) the engine started bucking, and the check engine light started flashing. I pulled into my office parking lot, stopped the car, restarted, and it ran fine (check engine solid now). Plugged in the obdii and it had active and stored misfires in cyls 1,2,3,7,10 (?!?! Not just one side!). So I'm at a total loss.

As far as the noise, as I Drove it home 30mi without engine issues, about two miles from the house, when stopped at the stop lights, I could hear an occasional growl or whirring buzz from under the car. When I pulled into the garage, I left the engine running and followed the sound to the rear axel area drivers side, maybe center of vehicle, but it was not as loud from the passenger side. Sounds almost like a muffled air drill at lower rpm. Not sure how else to describe it. It seemed to come on for a couple seconds very randomly. I doubt it's related to the ignition, but it's still annoying.

So HELP! What else could be going on with the ignition system? And what is this new noise I'm hearing in the rear?

Thanks in advance!

 

https://mbworld.org/forums/m275-v12-...misfiring.html

 

So perhaps the ignition voltage transformer that sends voltage to the coils?

 

just a SWAG

you were just in/under there the eve prior?

sounds like a boost hose popped off - check all connections

the difficulty starting would correlate to something not seated correctly and a lean draw, then the abrupt load unseated it more fully

again just a random thought

report back, fingers crossed for you... that's not a fun feeling, esp after what you've gone thru

 

Fuel pump? I keyed in on the noise description. The fact that the noise comes and goes at idle just seems odd to me. MB fuel pumps do whine (and the muffled air drill description is a good one), but usually consistently not intermittently. Maybe the misfire codes are a result of periodically low fuel pressure; just enough to misfire randomly. Would also explain the lack of 'umpf' when you punch it. Depending on the miles and fuel quality used, I'd check the fuel filter, fuel pump and/or fuel pressure regulator. Just my two-cents. Had similar effects (but no codes, obviously) in a '73 450SL. It was the fuel filter.
Cheers,
Jeff
PS - If this was covered in Das Geld's link, sorry. Didn't read the entire link.

 

Thanks for the suggestions guys. I just rolled 90,000 miles, but always use either BP or Mobil - 93 Octane fuel (or other major brand if those aren't available). I did notice when it misfired again today it was at startup after being run (warm). I was able to drive around all morning with no problems. I went to watch my daughter's soccer game, and when we went to the car, it wouldn't start...misfired again and would stall. Took about 5
tries before I finally kept my foot on the gas to keep it running to get it in gear. Sort of felt like an idiot being the most expensive car OBVIOULSY having problems.

Based on what you guys have said, I think before I throw $500 at a Voltage transformer, I'll try replacing the fuel filter and perhaps the crankshaft position sensor (??). I had a CPS go bad on my C32, but it flat out shut down when hot while running, not at startup.

I'll also double check all the connections when I installed the coil the other night...maybe I pinched something or forgot to plug a sensor in. I'm wondering if the new plugs I put in are fouled up now ?? (I hate to even touch those blasted coil packs again to look at them unless I have to).

Are the CPS and Fuel Filter easy to DIY, or is there something "special" I need to worry about?

 

Fuel filters are fairly straight-forward to replace. The bugger about 'em is the gasoline that inevitably leaks/spills. One has to really be cautious when changing fuel filters DIY. Personally, I have an Indie shop replace 'em for me simply 'cause it's faster and safer with the car on a lift then on jack stands. But the task steps are simple. Just keep gas spillage to a minimum.

Regarding fuel, the two you mention are good brands. But what I was referring to was the quality of the delivery of gas. That's determined by the station, not the brand. For example, one can have the finest fuel in the world, but if it's stored in tanks that have contaminants or delivered by equipment that adds contaminates, the gasoline is thus contaminated. Food for thought.

Cheers,
Jeff

 

check the fuel rail/manifold pressure before you throw random parts at it. simple gauge available at any parts store. check ign on static, engine running, "brief!" blip at wot. you should be seeing a stored code for any pump/pressur problems IMO. maybe when you go back over your work youll find somthing simple/obvious that wont cost anything but a little time.

 

roflmao (sorry)

I have soooo been 'there' (and as recently as Tue - d'oh - w/ the TR3, oh the joy... least w/ 'that car' it's all but expected heh heh)

too funny

what's not funny?

I swear this sh!+ is contagious!

I got a random misfire last weekend backing out of a parking spot (hot after an in/out), which I restarted and it went away and CEL cleared itself w/in miles.

Last night I got the exact same thing after an in/out.

I have 2 new coils, 59,999mi, hoping it's an abberration 8-/

sorry - tangent!

In you case, rule out the boost leak - your symptoms sound alot like it

Good luck, hope it's something simple (and hope for no further CONTAGION heh heh - jeesh!)...

 

Paul,
LOL! Yeah, you have to love those ironic situations! Can you explain what (where) I should be looking for the boost hose connection you're referring to? Is it something I could have tweaked as I was replacing the blasted coil pack? I'm frustrated that I've sunk the funds I budgeted for the ECU tune - AGAIN! I just want 60 days driving with no fuss! Is that too much to ask??

Jeff,
I agree with you about the indy mechanic install. I'll have my guy install the fuel filter when it arrives. I also understand what you're saying about the fuel delivery. I just filled my tank up at a different station and added a bottle of fuel system cleaner. Figured it can't hurt.

AH1W-COBRA,
While it's in, I'll have them check the rail/manifold pressure.
No codes aside from the last P300, P301, P302, P303, P307, P310. The fact that it's spread across both cylinder banks with two new ignition coils is what's frustrating me.

Thanks again guys, you're great!

 

Awww, shucks Mark. Now you're gonna give Paul and I big heads and inflated egos. LOL Seriously, good luck and let us know how it works out.
Cheers,
Jeff

 

no worries Jeff - I am most definitely not great

Mark-

Look @ the boost related items you tinkered with during coil install - there's a few bits under the airbox that run to the I/C that you removed to access... I'd confirm are all seated correctly.

All it takes is a slight pinch or twist of something to be 'off' a CHair (red headed) and you're drawing unfriendly unmetered air.

I know I busted the nipple off (like so many here have done I see) that sensor that runs off the small I/C hose when I did my coil. Dunno that'd cause your huge misfire issue tho.

peek around - remove that stuff and reinstall even

 

Well I got home and after she cooled enough to touch, I spent the evening removing everyfriggingthing again on the passenger side (intake, air connections from the intercooler, coil pack and even the spark plugs that were replaced in December) . I figured it's probably something on that side since that was the one I last tinkered with with the coil pack install. Plugs still look good (thankfully), I removed every sensor (the MAF pressure sensor - Paul I broke that stupid nipple off once too, intake temp sensor on the air box, and some other unknown connection - thin plastic tubes that had a "T" connection - crank case ventilation maybe??), reseated them, sprayed some electronic cleaner on the plug connections, let them dry, and plugged them all back in. I did notice after reassembly, when I squeezed the coolant hose running to the intercooler (the one closest to the center of the engine) it didn't feel like it had any fluid inside it, however when I gently pressed the schroeder valve, a little fluid would come out if I squeezed the hose. Is that normal? The engine was off and relatively cool, so maybe I'm just paranoid and the system wasn't charged.
She started fine (this time...but again she had a chance to cool down). Plugged the computer in and reset the engine light to get to a baseline. For what it's worth, the misfires that ocurred today were almost all different cylinders on both sides compared to two nights ago. I'll check things tomorrow when I can take it on the highway to the office. Crossing my fingers. Regardless, I still plan on replacing the fuel filter and crank position sensor anyway just for preventative reasons (can someone tell me where the sensor is located?). They should arrive next week. .

 

Mark,
While changing the crankshaft position sensor is probably not a bad idea, I think failure of the sensor - even intermittently - sends the engine into Limp Mode. Just an thought as I re-read your symptoms.
Cheers,
Jeff

 

Update...still misfiring...
Had my mechanic replace the fuel filter and crank position sensor. He also checked fuel pressure at the rail (no issues), and vacuum (no issues). He also said he doubted this was the cause because no lean codes were showing up. Then he pulled out both coils and inspected all the plugs I put in, checked the gap and their condition (no issues). He drove it around a day before calling me to pick it up (with no issues). I pick it up, take it for a 25 mile highway spin, go home and park int the garage. Everything seems fine. 1 hour later I need to run to the store. So. I go to start her up and I get the flashing mil with obvious misfires again...nurse her back to the mechanic where it is shut off and restarts just fine. Pull codes: P300 and a couple other cylinders 1,2,7,10 this time. He's thinking it's definitely an ignition issue suggested I replace the right coil pack again in case it was defective.
Ugh! So...Any Other thoughts or suggestions before I rip the damn thing apart - AGAIN???
Thanks!

 

So today while driving to an easter party, the car threw a P0410 secondary air injection error...would this contribute to the warm misfire or is this a totally separate issue?

 

Update for those concerned...
Reset the CEL, started the car, and ran at ~3000rpm for ~a minute in park per the indy mechanic's instructions to reset the CPS sensor (???)
Replaced the Coolant Temp sensor
Replaced the air sensor in the manifold
Replaced all four pressure sensors (both airboxes, pre and post intake in manifold under the voltage regulator module in the top center of the engine)
Ran 5 tanks of seafoam fuel cleaner

Knock on wood, the misfire has gone away.

The only variable that I can't control is that the last two weeks have been relatively cool outside (50-60s). When I had the last misfires, it was a warm week in the 70s. Time will tell, but I wanted to let you know. I did take pictures of the coolant and the air sensor. The coolant sensor had some corrosion on it, not alot, but some. The air sensor was definitely in need of replacement.

I haven't looked into the P0410 Secondary Air Injection System error yet...I hear the pump running every morning when I start her up. Have gone about 150 miles and the light has not come back on, so maybe a fluke? O2 sensors would throw a different code, right? (I have a concern the cats were damaged with the misfires). Live sensor data looks right on the computer when I plug into the OBDII, so maybe that's just paranoia on my part given that I'm out of Fed warranty period now (it's the EARLIER of milage or years, isn't it?)

Oh, AND the fuel pump noise has gone away after replacing the fuel filter.

 

What is the normal pressure at the test port on the fuel rail?
I'm getting about 16 psi, which seems low to me.

Thanks