1990 560sel missing
 

ok, here goes i have been on here alot with this 560. had a bad vaccum leak oround the injectors, new seals and o-rings. now it is missing. idle is at 600 steady no bounce what so ever. but it shakes like we are mixing paint or a 69 camaro. have put new plugs and wires. so where do i loook now? not burning oil, not running hot no smoke.

There are some rubber parts in the intake manifold, underneath all the fuel-injection stuff you see under the air filter: these could be leaking, as they are prone to do when they age. Sure it's not your plug wires, etc? Anyway, those rubber parts are worth replacing at this age.
One way to confirm a leak down under: no, I can't tell you, it's too risky.
My '86 420 was a known poor idler from new; I always knew if I could get my hands on it, I could straighten it out. Now (20 years later) it idles very smoothly, and the dealer who could not fix it when new is out of business. Hope this helps/encourages you.

what rubber parts are you talking about?

okay lets see if can find this miss.warm up car,apply emergency brake,remove air cleaner housing,get an open end 12mm wrench,put car in drive and gently let off foot on brake[emergency should hold it,if it won't you will need help to keep brake applied].now loosen one of the lines at the top of the fuel distributor and you should create an immediate miss that you can feel which will smooth back out again when you tighten the line back up.you need to do this with all eight lines.ideally when you loosen line you will have fuel leaking at the nut you loosen.if you find one that doesn't leak much fuel then your problem may be in fuel distributor.using this method you should be able to isolate the missing cylinder.

thats only for a fuel miss right?

right-----but you've done all the electrical?

found the reason for the miss. ran the engine and loosen the lines at the fuel dist and the 1st one on the driver side and the 2nd one on the passenger did not leak any gas and i loosen it a bunch so now what? am i going down a slippery slope?