C180 - Engine Misfire / Backfire

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Wully

Active Member
Joined
Jul 2, 2004
Messages
502
Location
Glasgow
Car
2002 W203 C220 CDI Avantgarde SE Auto
Guys
Looking for some advice :confused:

The car seems to have the following problems that relate to its running and I’d appreciate your thoughts.

I’ll show the results in the different situations:-

Idle in P - Lumpy, dips every few seconds and fire up again

D - Sounds like it's missing when pulling away, backfires then pulls no problem

Changing Gears in Auto - Backfire between changes if accelerating up or dropping down


Basically I really need to drive the car like a manual, when it drops down a gear for a corner for example and left in the drive position it will hesitate, backfire and then pull away.

A few things I’ve noticed, when its cold it runs quite well until I’m assuming the engine reaches the desired temperature - like an old choke, it then acts like that above.

In the last couple of weeks I’ve had the following replaced:-

Plugs / 2no Coils (no signs of abnormal wear to the previous plugs - improved running for about a week)
Complete exhaust Inc CAT (this weekend)

The only items I haven't replaced and I’m thinking of is the ignition leads and plug caps from the bottom of the coils.

The other thing I’ve noticed, it seems to have developed a metal knocking noise from the top front of the engine, could this be a tappet? It's more obvious at low revs and vanishes at higher revs.

The last thing I want to do is put it into a stealership, it’s covered 140k and had a valve replaced about 20k ago, MAS was replaced at the same time.
 
Hi Wully, sorry to hear about your problem.

There is most probably a lot more people here with more knowledge than myself, but here is a what I think it could be, mainly because it's happened to me.

It sounds like your Camchain Tensioner might be stuck, or broken. This will mean that at idle, usually the Camchain hits the side if the Engine Casing, because of no load. When this happens it can jump a tooth on one or both cams, putting your timing out, resulting in the symptoms you mention.

The one way you can check is by removing the Rocker Cover and feeling the tension on the Camchain, should be pretty taught.

Hope this helps, but as I say, this did happen to me but it wasn't a Merc.

And I'm sure there is someone else here that has had the same problem on a Merc and will be able to advise you accordingly.

Cheers, Bill.
 
If it's Ok when cold but more of a problem when hot suspect an air leak into the inlet manifold after the throtle body.

When on fast idle the leak has a lesser effect as more air is passed in by the throtle, once the engine warms then the throtle closes so the vacuum increases and any leak has a greater effect.

Just an idea.
 
Does anyone think this could be MASS related?
 
Wully said:
Does anyone think this could be MASS related?

Its the FIRST item I always remove and clean when a problem occurs. 5 minutes, no cost.
Fixed many a fault.

Bazzle
 
What do you use to clean it with?
 
Wully said:
What do you use to clean it with?

Aerosol brake cleen.
Spray on, drip dirt off, wave in air to dry.

Easiest way to remove is to undo 2 small torx on side of unit and slide sensor out.

Bazzle
 
I'll try that in the morning!

Thanks for the tip!
 

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