560 Rough idle

Rough idle on 560 has been a problem ever since I purchased the car last August. I have been in the trouble shooting mode reading the engine manual several times..I had found a bad throttle switch and leaking EHA. Replaced them, but the idle was still rough. This last week I pulled out the injectors and in looking down the holes I saw broken tips on the nozzle holders. I replaced all eight nozzles holders, guides and vacuum hoses on top of the injectors. That fixed it !! The engine has a smooth idle and the acceleration improved considerable. All this for a little over $50.00. The car is 10 years old with 130K miles. All the engine rubber is quite brittle. I think this could be a source of problems for all the old CIS V-8's. Thought I would share this with everyone.

H. O. Tyler
90 560 SEL 130K
85 300 SD 62K
83 240 D 260K

thanks for the information. might need it someday....

emmy
1991 560SEL 125K

[SANDEEP]

I HAVE A 300SEL 89 AND HAVE A ROUGH IDLE FOR A LONG TIME. THE TECH TOLD ME IT COULD BE THE MIXTURE CONTROL UNIT BUT DUE TO THE COST I DID NOT FIX IT. I DID HAVE MY INJECTORS CHANGED A FEW YEARS BACK. WHAT EXACTLY DID YOU CHANGE THAT CURED THE PROBLEM. APPRECIATE A RESPONSE FROM YOU.

I changed out the fuel injector nozzle holders and rubber vacuum hoses. This is a 560 V-8 gas engine with the CIS fuel injection. The 420 is simular.

[mihai914]

Can you please specify the symptoms of the rough idle because my 420 is having problems. It idles smoothe and like every five seconds it gives a jump shake like a piston just fired. Thank you.

Mike