230 Misfire

Canadian230

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Hi,

I am new to the forum and hope someone can help me out.

I have a 1977 230 4 Cylinder Gas (115.954 engine with a Stromberg carb). When it runs (after about 20 minutes) and the engine idles in drive (like at a traffic light) it stutters and misfires. Sometime very badly (so I have to give it gas to keep it lit) and sometimes not at all. When it's cold and over 900 rpm it runs perfectly.

Now I have changed everything I can think of (except the ignition coil). This includes rotor, cap, condensor, points, plugs, wires, cleaned the carb and replaced the diaphram, all the rubber air hoses are new, professionally cleaned the tank and fuel lines. I (and an experienced Mercedes mechanic) are at a loss as to why it still misfires when hot (which sometimes manifests as the RPM fluctuating by 100 rpm or so before getting worse).

Any suggestions? Could the coil be the problem?

Thanks.
 

meanie

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Sounds as though you may have an air leak (manifold leaks were quite common) or the mixture is just too lean.
Worth checking that the timing & dwell angle aren't fluctuating which would point to a worn distributor.
 

Sam.slc

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Would agree with meanie

I would agree with Meanie sounding like an air prob. Sounds like a Stupid question but have you recently changed fuel supplier or shoved Cat clean in her belly ?
These old dears can be awfully tempremental and if they don't get their normal food well ...Call for Matron
 
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C

Canadian230

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Thanks for the ideas...

One of the bolts that holds the two manifold halfs together is broken (the one with the ceramic spacer between them). There is no exhaust leaking through it, so I think it's okay. Could that cause a misfire problem?

I've added cleaners and octane boosts to the tank, so I'm pretty sure it's getting good fuel. Otherwise, all the hoses are new. I'll retighten the bolts to block and see if that helps in case there is a leak at the intake manifold.

Keep the suggestions coming...

It's a labour of love with this car, but I am determined to get it running!
 

Miffy

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Your Mercedes
CLK 320 CAB Elegance C208
an air leak would normally manifest itself with the engine hunting
 
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