ghitos73

Upon cold start, the truck would sound real weak and it would shake like it is going to die. After starting it up again a few hours later, it runs fine except the "Check Engine" light would stay illuminated.

I was wondering if anyone had any suggestions as to what it might be before I ended up spending a ton of money at the dealer. I wouldn't mind taking it to them, but they are several miles away.

One more thing, I used an OBD II Code Reader to tell me the fault code and it read "random misfire".

Any help would be greatly appreciated.

Rene

As I understand this may be:

a. a spark plug

b. a spark plug wire

c. or injector(s)

Hope this help...

Rene

theine

Yep, I would do as rene says.

ghitos73

Thanks for the good info guys. I decided to take the cheaper route ($6.99 ea) and buy all twelve spark plugs instead of buying the wires ($49.13 ea). I couldn't believe how much they cost and to think about replacing all twelve plug wires ($589). Yikes!

Anyhow, it took me 1.5 hrs to replace all twelve spark plugs. I bought the Bosch Platinum +4. One side was definitely easier than the other (driver side). I had to struggle when removing the spark plug wires.

After installing new plugs, I attached the OBD-II Code Reader and erased the computer codes. Not only did the "Check Engine" light disappear, but the truck runs a heck of a lot better than it did before. It has better acceleration and doesn't stall when I floor the gas pedal.

I will keep you guys posted on how it does later on ...

Again, thanks for the advice.

Mercedescl600

Reasons mine came on:

1. Gas cap wasnt on all the way.

2. Both O2 sensors were burned out.

I have 70,000 miles on mine.

ghitos73

Arg!! I cannot believe this. My "Check Engine" light came on this afternoon! I thought I nailed it by replacing the spark plugs. I have a new problem now ... Does anyone know what "Fuel Trim Malfunction" means? Please help.

Drew_ML

Replace the Mass Airflow sensor. I can almost guarantee you that it will fix the problem...replacing the spark plugs probably didn't do much at all, but hey it didn't hurt either.

Good luck!

JJunkins

If it was the Mass Air Flow Sensor, you would definetely be able to tell. Your car will not accelerate when you press the pedal. Well, it will, but only for a few seconds then it will become very, very sketchy and jerky. Sounds like your O2 sensors are gone. That happened to me as well.

Unfortunately, my "check engine" light did not come on when my Mass Air Flow Sensor took a hike.

ghitos73

Drew_ML: The spark plugs helped with the misfiring of the cylinders (#1, 5, & 6). Those codes (P0301, 0305, & 0306) have not returned.

JJunkins: Man, I cannot believe how much the MAF sensor costs. I called two MB dealers: they want ~$290 (US). A friend of mine has an older Audi, he paid $700 for his. So, I guess I shouldn't be complaining.

Anyhow, instead of replacing the MAF sensor, I cleaned out my air filter to see if it would do the trick. I cleared the code and the Check Engine light disappeared. The light has not returned since. I waiting to see if the MAF really needs to be replaced. I am not too sure it is the sensor because I haven't experienced a loss in acceleration or performance. I will run with it for a while and see where it takes me next.

JJunkins

My MAF went out on me on Labor Day, I was in Knoxville, TN and I live a little east of Atlanta. I had to call roadside assistance and they had to get someone to go to Mercedes of Knoxville to open up the shop for me. Luckily I could get my ML to their shop. My car was out of warranty and cost nearly $500 for the whole thing. I didn't pay it though. I told them to bill it to my home dealership. They paid it too.

My car is in the shop today. The BAS, ETS and ESP lights came on the other day and my brakes where grabbing awfully hard. Some thing about a sensor (figures) went out. This is the 2nd time for this. They brought me a 2002 C240. I like it much more.

ghitos73

Yikes! More problems with your ML ... I think you should go for that Audi S4!

Nano57

Hi guys i'm new to this game i have bought a 98 ML 320 some month ago and I've got to say its been running good so far, but the other day this light came on and even thou i had changed the spark plugs and cables as a matter of maintenance ($450), the light came on anyway, the funny thing is when this happens the RPM gage stops working also. Does anyone have any idea of what it is ? I'm just curious as to why the RPM stops working.

benz-tech

stop wasting money! 20bucks says you got into some bad fuel. take a piece of white paper, pull the engine cover off and the fuel rail cap. start the engine, place the paper under the fuel cap, press the schraeder valve with a little screwdriver, protect your eyes, the gas will soak into the paper but if there is water, it will bead up and be obvious. if it is clean, then you may have an issue with sensor adaptation- especially after a missfire. dealer only on that one, sorry. Mafs are a common prob but you usually have a few months of lack of power before they get to the point of causing a misfire.

99ML320

I love it when he chimes in, he's right to the point no BS and usually correct. Thanks for adding in on post like that where common misconceptions send us in 500 different directions.

I have had me CEL on for about a year (P071 and the other o2 sensor stuff) and I could honestly care less but with my little brother coming of driving age I guess he can get the 320 so I need to fix all of these little problems.

fizzle

coil packs.