1991 500sl hi all, please help. If I don't drive the car for more than 8 hours, the next time I start it, what happens is I feel like I'm in a tractor. The car shakes like crazy and it feels as if it loses power and turns off. It even happened in the freeway during traffic!!! Could this be related to a different problem I have, at times, while driving my RPM will suddenly drop and I have to force the vehicle to go and it eventually gets out of that mode but gets back what's strange is when it gets off its like a push from behind like if a gear is misfiring?? Also at times the car just doesn't start, I have to apply the gas pedal for it to start and sometimes that doesn't even help!! I'm so fed up but I love this baby

 

after it does finally start, how does it idle? does it shake or cut out while trying to accelerate or push down the gas. If it's a fuel pump it cango down hill pretty fast on ya. they can be pressure tested.