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Discussion Starter #1
98 ML320 cylinder problems

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So I drive an ML320, 1998, with 162k miles on it. I recently took a new job that requires me to commute about 75 minutes each way, so of course, it broke down. I'm trying to pinpoint what exactly is going wrong, before I start replacing everything.

When driving home recently, about 30 minutes into driving I noticed I wasn't accelerating as well as normal, and as soon as I would try to go up a hill, my speed would drop instantly. I could put the pedal to the floor, and the engine would rev to about 4000-4500, but the car wouldn't move any faster, and wouldn't shift. By the top of the hill, I was all but stopped.

A friend got a cylinder misfire error from a scanner, and I took it to the dealer to replace the spark plugs and spark plug cables. However, the next day, the same thing happened, at about the same time into driving. However, if I turned the car off and back on, it runs normal for a bit, but then returns to not accelerating up hills, just revving.

I have a few ideas in mind, but wanted to know if anyone has had a similar problem or experience with it.

edit: took it to autozone to do a scan, and have misfires on basically all cylinders. was driving slow and not accelerating well, but definitely not running only half the cylinders like it was while driving home.

Probably going to replace the coil packs, as they would need done soon anyway if it's not them.

Is it worth shelling out an extra $400 for OEM coil packs, or should I use ebay and get 6 for $100? Don't want them to crap out again after only a few miles.
 

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2000 ML 430
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1,588 Posts
I wouldn't go on ebay, go on autozone and search it for your vehicle, you might not get the bosch coil pack if you don't want to pay for OEM but you can get ones of a better quality that ebay for cheaper.
 

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02 ML320 06 ML500
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17,101 Posts
Do not replace coil or wires. This is probably a catalytic converter problem ad they will have to be checked before any replacement of parts.
 

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Discussion Starter #4
just curious, what leads you to the cat? I've gotten multiple opinions from a few people, and they're split between coil packs and the cat.

Also, should the coil packs be replaced after a certain number of miles? If so I'll just get them anyway and fix the cat...really want this issue solved soon.
 

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1999 ML430
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1,739 Posts
You can't just go throwing money at parts to solve problems. My 99 ML430 has over 300,000 miles on her and still has the ORIGINAL coil packs. Yes that unusual, but they can last a long, long time. Plus, when you replace...replace the faulty unit , not all of them, unless necessary.

Spend your money on a good diagnosis of codes and take it from there. Many of these issues have been addressed on this forum. If you will post results and steps you have taken, you can save some serious money AND have your ML running well again.

P.S. If those are original cats, they very well could be the source of your problem. The catalytic converters have a history of going bad. Just had to replace one myself.
 

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02 ML320 06 ML500
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17,101 Posts
just curious, what leads you to the cat? I've gotten multiple opinions from a few people, and they're split between coil packs and the cat.

Also, should the coil packs be replaced after a certain number of miles? If so I'll just get them anyway and fix the cat...really want this issue solved soon.
If you are getting misfires on every cylinder, do you honestly believe that every coil went bad at the same time?

Clogged cats. cause back-pressure into the engine causing misfires. But if you want to replace every coil then go right ahead.
 

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89 300E, 98 ML320, 2010 C300 sport, 92 500SL, 84 500SE (Eurospec), 2008 C300 sport
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43sqd is right on the money. Same thing happened to my ML...hit the throttle and no action. It turned out to be my cats.
 

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2000 ML320
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i'm halfway getting through this same situation-

i got codes for cylinder 1 2 and 3 misfiring at the same time, happened out of nowhere and left me stranded, at a gas station not far from home (thankfully).

the engine was acting CRAZY when I tried to drive it and was a struggle getting it in the garage, removed the forward oxygen sensor and it was doing better not bucking as violently with the plugged cat.

almost got the dang thing out, just stuck on the muffler coupling thinger! she's stuck on there good so i'm just soaking it in some liquid wrench over night and going to try some more while i wait for the part.
 
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