C-Class 1999 W202 Misfire Problem

[MercedesBeats]

Hi all,

This is my first post so please excuse me if I sound like a noob.

Car Info
Model:C-Class C180
Year: 1999
Type: W202
Engine: M111.921

I purchased a C180 earlier this year. It's been running really well for months however it's recently developed a bit of an issue. Over the last couple months, if I try to drive on a cold engine, the car just jerks as if it's got no power whatsoever. It won't accelerate at all, almost as if it's not being given any fuel. The only way to drive it is to accelerate from 900rpm - 1500rpm and then change to the next gear and so on, until you reach road speed. However, if I start the car and allow it to warm up to 90degrees before driving it, it performs pretty much fine.

Also, regardless of the above, another issue began occurring at the same time. When driving on Motorways, the car randomly loses power at around 70-80mph. It's only a very short loss of power and it can be regained in a couple of seconds by releasing the accelerator and then pressing down on it again slowly and gently.

In general, the car itself feels quite under-powered. I understand it's a heavy car but I have a strong suspicion that it's not giving me all the power it has under the bonnet.

I didn't really attend to the issue initially because I knew the car was due for service shortly. Anyway, I had my Dad take the car for it's service and MOT last week at a family friend's garage. It passed the MOT without issue. It was serviced also and was it was plugged into the Mercedes Star Diagnostics system. The mechanic explained to my Dad that a couple of cylinders were misfiring. He attended to it and said "It's fine now". I suspect he changed the plugs. Being a family friend, I was charged very little for all the work and as a result I can't really complain. Also the garage is pretty far away and going back there comes at a high cost for me.

My Mum's brother is a very experienced mechanic also, and we met over the weekend. He explained to me that I should just change the plug leads as the car sounds like it's misfiring and the leads sound like the culprits. When I inspected the engine, I couldn't identify any traditional plug-leads. So I called my uncle back and explained what I could see. He then advised me to purchase 1x Ignition Coil Pack and replace one of the existing ones. If I noticed a difference, I should consider my problem solved. If not, he said I should put the original coil pack back, and replace the next one instead and so on until I identify the faulty pack/s.

He said, they're really easy to swap. So, I tried to identify the packs. I couldn't work out where they are and how to access them. I'm not a dufus and have previously serviced my older cars with ease. However this is my first Mercedes and I'm out of practice. I've attached pictures of my engine and would appreciate any advice, direction & guidance any of you can offer me.

Many thanks & kind regards,

Mr Beats

[martyz]

Sounds like mass air flow sensor going bad,many posts on here with symptoms you are experiencing

[martyz]

Have just seen it's your first post, just a tip, introduce yourself in another post,some may be offended by you coming straight in with a problem.

Welcome to the forum

[grober]

This is a well known problem with these cars. There are 2 coils which each fire 2 cylinders/plugs. They are located under that plate on top of the cylinder head cam cover. Its held on by 3 or 4 allen/torx headed bolts. You need to remove the cross engine intake pipe. Once the plate is off you will see the plug leads and coils quite clearly. Any of the components can be faulty including the low voltage wiring from the engine ECU--- They tend to fail due the increased heat from the engine. Lots of posts and pictures on here about it-- it will pay you to read them.

THIS IS FOR AN SLK but same principles apply http://www.benzworld.org/forums/atta...y-1999-slk.pdf

[andy27168]

Hi,
If you are going to replace the ignition leads bear in mind you only have two of them, but do not forget to replace the plug caps which are fitted actually under each of the coils.

[MercedesBeats]

Thanks for your help Grober. However that PDF link seems to have been shortened and doesn't work for some reason. Can you maybe re-post the link for me? Thanks again

[MercedesBeats]

Thanks Martyz, I thought it might be related to that. I think I'll go down that road if the leads and coils don't solve the problem first.

[grober]

Originally Posted by MercedesBeats

Thanks for your help Grober. However that PDF link seems to have been shortened and doesn't work for some reason. Can you maybe re-post the link for me? Thanks again

TRY POST #38 IN THIS THREAD FOR THE LINK.
Tech Tips and such.............. - Page 4 - Benzworld.org - Mercedes-Benz Discussion Forum

[MercedesBeats]

Excellent! So useful! Thanks Grober. You rock!

[MercMania]

i had a similar problem on my car i replaced the air mass sensor since then had no probs i suggest u try that first cheaper option