Hello guys. hope someone can help me out here. I have a 1989 560sel that wants to stumble on takeoff. it dont matter if its hot or cold. there are times that it will run like there was nothing wrong at all. it boggs down and sometimes dies at stop signs. it started doing this about a month ago but I never had time to look at it. about the same time this started I could smell raw gas inside the car but found no leaks and I noticed this more often when I filled the car up, 2 days ago when I filled up, I didnt notice the smell of raw gas at all. my girlfriend used the car while I was out of town and she put regular unleaded in it instead of the premium. has that messed up something onmy car. I have only replaced the plugs at this point. it also has a rough idle now, like a light miss. I have since filled up with premium 93 octane but no change. any of you 560 owners have this experience with your car. this is not a daily driver, so it does sit in the garage alot. any hints or sugestions ???? also, I have noticed that when the car in running and in park, I have heat, but the minute I get out of the driveway and go down the road, the heat goes away andnothing but cold air at that point. thats about all the trouble I am having with this car.I am stumped at this point. Please help. Thanks

 

well if ya put regualr in 560 you'll notice a difference especially if ya lead foot. See lower octane rating can cause pre detonation as in the fuel air mixture ignites too early and can mess stuff up after a while in some cars. In the 560 using wrong octane can leave a slight rough idle that can drive a mechanic insane trying to fix.

Smelling raw gas indie that car at any moment is not good.

The sluggish feel can be from a failing fuel pump.Or a clogging fuel filter.When it is not working properly but working, it may be able to deliver fuel fine at idle but when you press the gas, it can overload a bad fuel pump and cause not enough fuel to get to the engine. When it's electrical, the fuel pump can work erractic sometimes working fine, the next too slow, sometimes not at all and then fine again.

and when you sit the car in the garage do it sit long enough for the battery to run dead because jump starting these beasts can cause all type of electrical gremlins.a goodthing is if the car is going to sit a while, disconnect battery or even best is to get one of those devices that holds the battery charge.

The heat might be a vaccum problem.