MBCox

Does anyone know what causes a misfire when engine is warm, 300SL 24 1991.

cliffyk

You have asked a rather broad question, here is a rather broad answer (pretty much in order of what I would check first):

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Bad spark plugs;

Bad plug wires;

Bad distributor rotor;

Bad distributor cap;

Bad ignition coil wire;

Bad ignition coil;

Bad fuel filter;

Clogged air filter;

Bad fuel;

Low system voltage (possible battery/generator/regulator problems);

Low compression when hot (worn piston rings/leaky valves/bad head gasket);

Worn timing chain;

Worn timing chain guides;

Worn crank/cam pulleys;

and a myriad of other problems...

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1. How many miles on the car?
   
2. When were the spark plugs last changed?
   
3. When were the plug and coil wires last changed?
   
4. When were the distributor cap and rotor last changed?
   
5. Has the ignition coil been tested?
   
6. How many miles on the car?