Rough start

[mbLova]

hey guys, the past couple of weeks, what happens, very intermittenly very very, like 2 days every week, is that i have gotton a rough start. no warning lights, no cel, what happens is that ill turn the key(1999 c280) all the way and it sarts, for like literally a second, then itll shutoff. so ill turn the key all the way to 1 and take it out. ill put it back in and the car starts normall, but i can tell that there is a very very slight rough idle, so small that i can barely tell unless i really really listen to the engine. this car has 57.7k miles, i got it when it had 56.2k. i got in jan this year and i had it thoughrouly checked out by the stealership. they said everything was in tip top shape(knocking on wood) but now this has started to scare me, im a hs grad( just grad this year) and i realy wanna keep my car in tip top shape. hope you guys can help me with a solution.



thanks

mblova

[jnenad16]

I would start with something simple as a tune up, including spark plugs, fuel filter, air filter, and a fuel system cleaner. see if this helps, if not, I would guess that the mas air sensor(MAS) or crank position sensor might be failing. also, make sure all the sensors are securely connected to their connectors.

nenad

[mbLova]

hey thanks for the help, i know this may sound stupid, but how would i go about checking all of these things? how would i check the spark plugs and all the sensors and what should i use as a fuel system cleaner?
i know, i just recently got this car and i just graduated hs, im slowly learing all the stuff(i do know where the maf) is ... but thats about it. i woudl appreciate any help i could get..

thanks

mblova

[jnenad16]

like I said, do a tune up first. if that doesnt fix the problem, then inspect the connections on every sensor you can see on or around the engine. I also forgot to mention, check every vacuum line and its connections you see for cracks or if its unplugged. if everything checks out, then the most likely cause would be a failing mas or crank position sensor. as for the fuel system cleaner, you can pick up a bottle at any parts store, my preffered brand would be chevron or greased lightning.

nenad

[SLAMMED_C]

Originally posted by mbLova
hey guys, the past couple of weeks, what happens, very intermittenly very very, like 2 days every week, is that i have gotton a rough start. no warning lights, no cel, what happens is that ill turn the key(1999 c280) all the way and it sarts, for like literally a second, then itll shutoff. so ill turn the key all the way to 1 and take it out. ill put it back in and the car starts normall, but i can tell that there is a very very slight rough idle, so small that i can barely tell unless i really really listen to the engine. this car has 57.7k miles, i got it when it had 56.2k. i got in jan this year and i had it thoughrouly checked out by the stealership. they said everything was in tip top shape(knocking on wood) but now this has started to scare me, im a hs grad( just grad this year) and i realy wanna keep my car in tip top shape. hope you guys can help me with a solution.
thanks
mblova
you could have worn motor mounts.. causing the slight rough idle.. aslo it could be a really slight missfire.
have the motor mounts checked out.. as long as the check engine light isnt on.. its not a problem..
but I think the best thing to do.. since you only bought it at the begining of the year and havent put that much mileage on it.. is to take it back to where you got it from and have them look at it.
as for the starting and then quickly shutting off.. could be a problem with the key and EIS (electronic ignition switch) they may be seeing eachother perfectly fine while cranking but when it starts it shuts off.
or I know on the W208 clk's, the 320 motor more so then any other.. the engine would turn over when cranked, and start breifly.. but then shut off.. basically the starter and ring gear were dragging, and the rpms would just breifly.. just enough that the starting circuit had thought the car was running (as soon as the rps jump above 500 or 600 rpms the starter circuit then stops energizing the hold in winding so the starter wont be engaged any more and not damage the ring gear or starter.
the fix for this problem was to lube the ring gear with a special grease.. and it fixed the problem.
just a couple thoughts for ya.. but Id take it back to where ya got it from and tell them whats happening.. they may do the things for free since you only bought it at the begining of the year, or if there is warranty still on your car then you dont have to worry either!