Mercedes: Mercedes Benz 450 SLC 1978, oxygen sensors, traffic advice

Question
Hi there,
Bought this car yesterday and it starts in one shot. Runs smoothly a bit and then begins to lose power despite acceleration to the verge of stalling. Seller did mention the spark plugs need changing. Do you think it may have other problems? What do you recommend? 250,000 kms. All original. Do you feel a tune up and change of spark plugs will make the difference? No smoke. No leaks. Just won't pick up and car shudders a bit when in halted in traffic. Advice would be greatly appreciated.

Answer
Salman,
Definitely,I just installed plug in my 86 420sel and it make a drastic improvement in the starting and performance. The plugs had in excess of 90,000. And in good shape except the gap was double the recommended because of use. You need to determine the proper plug for the vehicle base on the manufacturers recommendation for year and model. Do not depend on the ones removed to provide that info. I purchased NGK over Bosch because of the expense and they seem do the job.

After changing the plugs, and air filters too if they have not been changed,  and the problem still exist.
Oxygen sensor and or Catalytic converter if it has one may need checking.
If the catalytic converter is clogged, it will cause back pressure and not allow the vehicle to breath.
The Oxygen sensors adjust the mixture depending on the amount of oxygen read in the exhaust if it is cooked then the vehicle tends to run rich.
Good Luck
Rob Let us know how it goes>>>