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Investigating a mild but persistent engine stutter issue on my Mercedes

It's not much and my wife doesn't even notice it. But I do and I will keep at it till I find the problem.

BHPian Jeroen recently shared this with other enthusiasts.

Today I decided to investigate the persistent problem on the W123. I have been after this for several years now. When driving at a steady pace, the car/engine hesitates/stutters a bit.

It's not much, my wife doesn't even notice. But I do and I will keep at it till I find the problem. I got a bit of renewed inspiration after the technical day of the Heckflosser club at Cor de Jong, I showed a few posts earlier.

I had already agreed with Cor I would call him to arrange to come and see him and see if we can fiddle some more with the ignition and CO.

Today I decided I had better check everything one more time.

I have done this so often, I can almost do it with my eyes closed. Took the air inlet filter and its housing and associated pipers off, took out the spark plugs and removed the valve cover.

I made a list of the various measurements to check and torque specifications to put everything back together again.

When it comes to the spark plugs. The good news is, the tips look great. The gap is still spot on.

The bad news, as you can see, the thread and body are very dirty. I found them all loose!! I could just turn them by hand!! No idea how that happened. The last time I had the spark plugs out, was when I was working on the carburettor and dynamo with my friend Cees.

As it so happens Cees is arriving later today and I will blame him! What are friends for? We are taking his Volvo to another friend of ours to get a new exhaust fitted.

During the technical day, Cor also spoke about how an old worn distribution chain might cause problems. As the old chain stretches the timing between the camshaft and crankshaft will be off.

As some of you will recall I did renew my distribution chain a while ago. Both Peter and Toon had helped me, and we did have some issues regarding the timing at the time.

So I decided to check once again:

Here you can see the crank in the top dead-centre position of the first piston, as marked on the flange.

When I checked where the camshaft mark sits I noted this, which is incorrect!

So I slowly turned the crank a little further, just under 20 degrees

When I look at the camshaft in this crank position I see the mark lining up as it should!

My conclusion is that the timing of the camshaft is off. As it so happens one tooth is the equivalent of 18 degrees crank. So this can be solved by taking the chain apart, resetting it one tooth and clamping it down again.

Luckily I still have some spare chain links and bits.

I am going to think it over a bit more and ask some other knowledgeable folks what they think. Can this be the ultimate cause for the slightly less-than-perfect running of the engine?

More to follow.

I also put the Ford Fiesta Cutaway compressor together. Cleaned it with various detergents and air-driven steel brushes.

These are just the three main body parts, I have left everything else off for now.

On Friday I am planning to take it to my favourite DIY sandblasting place.

So I carefully masked some bits and filled up some cavities that should not be blasted. All ready for some sandblasting!

Check out BHPian comments for more insights and information.

 
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