merc83055

Hey all! I'm hoping that the smart people in the forum can help me with this one. I have a 1994 s420. When I put any octane gas in it, including 93, there's a hesitation when I'm stopped light or I'm just taking off. It feels like a misfire. If I put octane booster in the car the car runs perfectly fine. I'm fine if I have to put octane booster in it but it seems strange to me that I would when I'm putting the highest octane gas I can find in the car. I still will do that I'm not trying to cheap out on the gas I would just rather not have to put octane booster in it as well. Here is a link to a video I made to show a friend

https://youtu.be/JJXNjqWmaWk

JohnLane

Age of spark plugs? Good place to start.

Alex-587

I agree with the above post, Check your sparkplugs.
Not only will they cause a misfire but also rough idling or difficulty starting the vehicle.
Another part to check (or just replace to be sure) is the crankshaft position sensor.
This was an issue on my 300SE and caused the same problems as you have described.
(Misfire when moving off or taking a long time to start, it will just keep cranking. Mine actually stalled on an intersection when trying to move.)
These are more difficult to test and may even produce normal readings at slow rpm, thats why I suggest replacing it.