annoying miss! - PeachParts Mercedes-Benz Forum

dwcars · #1 06-08-2009, 07:30 PM

My '88 560SL has an intermittant miss that is getting on my nerves. After driving at 70mph for a few miles, I have an intermittant miss while sitting at at light. Having done no diagnosis, I don't know whether to look to the fuel delivery system or to the ignition system. Since it is a dead miss and not a stumble, I would guess it to be ignition. Anyone have any thoughts?

jplinville · #2 06-09-2009, 10:56 AM

Quote:

Originally Posted by dwcars

My '88 560SL has an intermittant miss that is getting on my nerves. After driving at 70mph for a few miles, I have an intermittant miss while sitting at at light. Having done no diagnosis, I don't know whether to look to the fuel delivery system or to the ignition system. Since it is a dead miss and not a stumble, I would guess it to be ignition. Anyone have any thoughts?

Mine used to do this and I traced it back to a vacuum leak on the back of the intake that is hooked up to the economy gage. The rubber elbow gave up the ghost...$2.98 fix at the 'Zone and all was good.

Paratroop · #3 06-09-2009, 10:57 AM

When was the last time you changed plug cables?Rotor Button,Dist
Cap??Check the easy stuff first.Heat and old cables build up resistance.

Philip J · #4 06-23-2009, 06:07 PM

I have the same problem with mine. I have done a complete tune up ,also have run injector cleaner[tectron] through it a number of times,Has anyone used acyletene to find vacuum leaks? Philip

timm9 · #5 06-23-2009, 06:38 PM

Philip,

You are very brave to use acyletene...

I might suggest you try a "smoke" test at a local shop. Far safer, with much better results. Plus you drastically improve your chances of driving your car after the test.

ctaylor738 · #6 06-28-2009, 02:24 PM

A dead miss can either be a plug not firing, an injector, or the valve for that cylinder in the fuel distributor.

The best way to check the plugs is to clip a timing light on each wire at idle when it is missing and see which one is not firing.

You can check the injectors by loosening the nuts on the the lines on top of the fuel distributor one at a time, again with the engine missing. If the miss does not change, you have found the bad cylinder.

Then you can swap the injector to a cylinder that is firing. If the miss moves to that cylinder then the injector is bad. If it doesn't then the FD has gone south.

Be sure to have rags available to catch the fuel.