jpniner

Please help, yesterday my car started jumping in parking lot in idle and first gears and CEL came on. Got it checked at autozone and it read out "Cylinder #2 misfire"....is this probably the spark plugs? the car has 95k miles on it, 99 ML320

rcltrh

Could be a plug, plug wire, but more likely the ignition coil for that cyl. going bad.

jpniner

thanks, i'm going to get the plugs changed since its due for a tune up anyway....will get the ignition coil checked for that cylinder too.

is the ignition coil expensive?

PaulX608

I think I paid $85 or $90 for the coil I bought. Didn't fix my misfire, though. But a $45 pair of plug wires did. I've talked to a few techs and they told me the wires are a definite weak link in this igniton system. I plan to replace mine as a set when I do my plugs. That'll be next year when I get to 90k or so. Or the next time I get a cylinder out!

rcltrh

True, wires will definitely cause that problem, but unless you have been under the hood messing with things generally I havent seen one just develop a total rough running jumping CEL type misfire problem all at once. Generally they go bad over a few weeks once they start. When a wire first starts to go bad I have noticed an occasional stumble, or idle jitter or feel a slight bump on the pedal when accelerating. That's not to say that it couldn't be a wire though. If circumstances were just right for the connection to break then it would give that symptom. I'd pull the engine cover off (just lift it up and off) and look at the coil for cylinder #2 (they are labeled on the manifold) and trace the wires to the plugs as well as to the harness and see if anything was loose. Look at the coil itself for cracks. Also, wait until nighttime then go out and start the car with the engine cover still removed so you can see the coils in total darkness and look for blue or blue-green glowing or arcing around that coil.

jpniner

well it wasnt the plugs, got those replaced since I was due for a tune up anyway.....I found the ingition coil's online, whole set for 175 bucks, debating buying those or taking it in to dealer to diagnos the problem. I'm generally skeptical of shops and figure they'll hose me if they can.

this problem started right after I filled up the other day at a citgo(I did put 89 octane gas in).....soon as I cranked it the CEL was on and it was jumping.

rcltrh

Oh. Well that may be your problem. I have never put anything but 93 in my ML so I have never had the chance to experiment, but my C220's CEL will come on if I even put 91 in it (and it does it every time) although its code reads knock sensor whenever this happens (if I am in an area that does not carry 93 oct and I have to use what is available). Put some Lucas Octane booster in your ML and see if it helps.

jpniner

well I've put 89 in it for a year now to save money since gas is high....anyway, I put some octane booster in, no help. any suggestion before I buy the coils?

rcltrh

Bad gas? Water in the gas from that station? Fuel pressure regulator? Fuel filter clogged by any of the above? They say the fuel pressure regulator on the fuel rail on C280 6 cylinders will cause the misfire indicator because on those cars something happens if it senses not enough fuel pressure it cuts out one cylinder which gives the misfire reading, but I have no idea if this same scenario holds true on the ML 320 6 cylinder. I would hate to spend $175 on a set of coils if it was fuel pressure, fuel filter, or water in the gas. At this point you are kind of just tossing money at it trying to blindly luck out since there are more than one variable. Had this occurred just during a trip to the mall without any gas being added or anything I would think wire or coil, but since it started after refueling (with low octane fuel) it could be bad gas, clogged filter, water in the fuel, etc. How far are you from your MB dealership? It might be worth a trip just to let them diagnose if nothing else. You could always buy the part and install whatever it is yourself and just pay them for the diagnosis. They can check fuel pressure and ignition coils pretty quick. Is it driveable?

PaulX608

You put 89 octane in it to save money? It's a ten or twelve cent difference per gallon. Maximum savings per tank is about $2.00. So, you used fuel that doesn't meet your engine's minimum requirement and risked possibly serious damage for $2.00 a tankful? That seems exceptionally foolish to me.

jpniner

I kinda think it could be bad gas, I only put a quarter of tank in it but it was Citgo which I usually stay away from b/c of Chavez....it was alot cheaper than the other stations....maybe I know why now?

Car is driveable, especially on highway....just jumps/shakes alot in park or while stopped...everytime I call the MB dealership to try and get them to schedule maintaince they always tell me they are booked up for next 2 weeks, last time I hung up on them. I talked to one of their mechanics once and he told me to just show up and not call.

jpniner

I put 93 in it from time to time, generally I've always felt this was just a scam to try and get you to buy the more expensive gas and help create the high-end price point for mercedes and other luxury cars. I've never had problem with 89 in this until possibly now. I do mix it up between that and 93 though.

rcltrh

Put you some Lucas fuel treatment with water remover in it, fill it up with 93 from something noteworthy (Shell, Phillips 66) then drive it a bit. If it was really bad gas or watery gas it could take a bit to work it out of the system. I have learned the MB simply do not like low octane fuels - especially the C220 being a 4 cyl it needs all the octane it can get. I can use it in the Lexus but not in the MB. I have never even tried it in the ML since it is so sensitive to everything. I think ML's will throw a CEL for sunspots

jpniner

I did what you suggested, lucas treatement and got a half-tank to top off of 93 from shell.....noticed an immediate difference....its still misfiring though but not near as bad as it was, big difference. unless it gets worse I'm going to drive it like this till i use this tank up and put more treatment and 93 again and see if it does trick, before i go to dealer.


note: this only time I've bought CITGO gas(and only b/c of price) since I found out they are Venezuala's company, Chavez is a lunatic commie *******....we should boycott them for that alone but none the less it appears they are putting water in their gas

rcltrh

Cool. Let us know how it goes. Like I said, it might take a tank or two to clean out really bad fuel or really watery fuel and if it was really bad fuel (stirred up crap off the bottom of the holding tank) it can even clog your fuel filter with a thick gelatinous gunk, but let's hope it wasn't that bad and will work its way out. My ex's mother used to work at a service station (phillips 66) and said people would be shocked at what comes out of the bottom of the in-ground tanks when they pump it out every few months, and Phillips 66's are usually very good stations. She showed me a sample once of a container full of blackish jelly-like watery goo that came out of the bottom after a cleanout and their tanks were less than a year old and it was the premium tank. Hate to think what lies in the bottomr of less than scrupulous stations' tanks.

jpniner

well this thing is still misfiring, but I still think its bad gas that just isn't working its way out. took to dealer monday and they thought same and told me to go another week or running 93grade through it.

I filled up monday with Shell 93 V-Power, immediately it was hitting on all cylinders again but a few minutes later it started misfiring again. still not as bad as it originally was when I filled up with the bad gas at citgo.

any suggestions on cleaning this thing out?

rcltrh

You may have gotten ahold of some from a tank that had a large pool of water in the bottom - happens frequently or so I am told. If you got a good dose of water in the tank, you may just have to keep adding that alcohol based fuel "drier" until it works it way out. It's pretty cheap at any store, so add some of that every tankful for the next few weeks and see if it gets any better as you drive.

jpniner

well i put some ISO HEAT in it last night, hasn't made any difference yet but I'll go for another fill up and iso treatment and hopefully it will clear it out finally.

rcltrh

That would be my approach. One time a few years ago (actually many now that I think of it) I filled up at this crappy looking out of town station (but I was on the big E) in an old 86 Toronado (which was less than a year old at the time) (I actually loved that car) and had the same problem. Finally had to take it to the olds place as the tank was mounted underneath the vehicle inside the X frame and was inaccessible. They removed the tank and when they emptied it out there was almost 2 gallons of black, inky looking water in the bottom that smelled really bad. They said this was typical of iron tanks in the ground when the moisture eats through the internal lining. I have never bought gas from anywhere but reputable places ever since. Even still my ex mother in law workd for Phillips 66 in a new station and said that if the lot seals aren't just right that rainwater gets in every time it rains and they have a pump thing they turn on to suck it out.

jpniner

well the ISO heat hasn't fixed problem, its actually gotten a little worse. I drove an hour away last week on interstate and it got pretty bad and when I got off highway it basically lost almost all power and eventually cut off in parking lot, I restarted it and it was fine though.

I'm thinking now it could be the fuel fiter or something along those lines. guess i need to atleast get it diagnosed, if its the coils I'm changing them myself.

My ML

I know what your talking about the same thing happend with my ml320 2000model 66k and its not the leades it your fuel pump i got my changed and now it all ok just take it to your mercedes benz dealer and theyl do it for you it will cost u around $400.

My ML

when this first happend to me i was going up a mountin sudenly i lost all the power and straded shacking i was full imbaresed even havy trucks over took me. its your fuel pump or either your fuel filter better get them both change thats what mercede did for me.

rcltrh

Yeah, at this point I would think bad gas would be out of the system. Now it could have been initially some dirty fuel that has since stopped up your fuel pump screen and/or fuel filter, but those two do seem to be what I think would be your first things to check. They can do a pressure test on the pump/filter/regulator to see how they are reacting and go from there.

Gabe

Check your vaccuum hoses, I just fixed that same problem in my 98 SLK230. The Fuel Pressure Regulator relies on vaccuum pressure to work correctly and the hard plastic hoses can get really brittle and crack.

Detari_SR

JP,

I had a simmilar misfire issue with my #8 cylinder. I red here in the forum, and learned that that wires are the weakest link.

I replaced the wires, and while at it, I replaced the plugs for that cylinder also. Easy fix.

You can diagnose the problem by switching the wires with the ones from another cylinder. Same thing with the ignition coil.

I hope this helps.


-----
2000 ML430
78k miles