Idle surge and lond start - PeachParts Mercedes-Benz Forum

danieldono · #1 10-20-2004, 05:19 AM

Had my '93 sl 500 in the garage now for two days. they have diagnosed it and the merc computer has told them to check most of the sensors. turns out all but one are definately new and the crank sensor is difficult to tell, so dont know if that too has been changed(Bought the car three weeks ago and dont have any history).

Problems are still, surging at idle and until about 1500rpm
rotates about eight times before starting but if she stalls starts straight away.

my garage has told me that they are opening the motor to check the timing. aparantly if the timing is out then rough idle could occur. also if timing is right then the crank sensor will be replaced. this is starting to cost a fortune. anyone know any experienced money saving tips here or do i just go with it. by the way garage is trustworthy, worked on my two ML's as well as wrangler and G wagon.

Ps plugs, rotor and rotor cap have all been replaced.

anybody??????????????

G-Benz · #2 10-20-2004, 10:33 AM

Only real suggestion I could give to your techs is to check for vacuum leaks...idle surging and rough idle is pretty much a symptom of that. Check the intake manifold and vacuum lines for leaks. You can spray a bit of water near those areas to see if the idle changes...if it does, you've found the leak.

nglitz · #3 10-20-2004, 11:00 AM

A little carb cleaner sprayed on a vacuum leak will increase the rpm for a few seconds. Good diagnosis tool.

An evil coolant temp sensor caused rough idle & hard starting in my older 260. Not the same, I know. Just a thought.

danieldono · #4 10-20-2004, 11:13 AM

we think we have found the problem.

told the garage to go with his gut feeling consideringi dont have an open budget. he opened up the front end and found the cam belt tensioner to be weak. aparently the timing was out one tooth so it would seem we have found the problem. they are busy putting the pieces back together and i am waiting to hear.

will let you know.