MBClub UK Forums - View Single Post - Warm idle too slow

Brabus3.6 · 30-12-2004, 09:26 PM

An update. Over the last couple of days the car has worsened, it will definitely cut out if I don't right foot accellerate and left foot brake. I decided to buy a cylinder compression tester. The procedure I followed was remove all spark plugs, coil lead and fuel plug relay, then screw in and test cylinder compressions.
The results surprised me as I expected low cylinder compressions. The specced cylinder compression for my engine is 10.1:1 up from the 300's 9.2:1. The actual compressions I read from cylinders 1-6 were: 12.5, 13, 12, 11.5, 12, 10.75. So hopefully Ian was correct when he mentioned the valve clearances as excessive clearences will give higher compression. After the valve's were re-seated the all the clearances became too small so I had to loosen all of them, perhaps all too much. I'll re-check them tomorrow. I would have thought if the valve clearances were out the engine would be noisy though as remember this happening on the M110 engines, my 103 runs fairly quietly. Does anybody know of a site that explains clearly how to get valve clearances 100%?!
I have attached a picture of a spark plug that just came out. Unfortunately the picture isn't great but the plug tips look fine however the base of the plug, bottom of the thread is blackened, its smell I cannot make out. Could be carbon or oil fouling. The valves have just been re-seated etc. so I guess it's either incorrect valve clearences or an overly rich mixture?
Thanks & enjoy yourselves tomorrow night!

30-12-2004, 09:26 PM	#13
Brabus3.6 Hardcore MB Enthusiast Threadstarter Join Date: Apr 2004 Location: London/Oxford Car: 1989 Brabus 3.6 Saloon Posts: 109	An update. Over the last couple of days the car has worsened, it will definitely cut out if I don't right foot accellerate and left foot brake. I decided to buy a cylinder compression tester. The procedure I followed was remove all spark plugs, coil lead and fuel plug relay, then screw in and test cylinder compressions. The results surprised me as I expected low cylinder compressions. The specced cylinder compression for my engine is 10.1:1 up from the 300's 9.2:1. The actual compressions I read from cylinders 1-6 were: 12.5, 13, 12, 11.5, 12, 10.75. So hopefully Ian was correct when he mentioned the valve clearances as excessive clearences will give higher compression. After the valve's were re-seated the all the clearances became too small so I had to loosen all of them, perhaps all too much. I'll re-check them tomorrow. I would have thought if the valve clearances were out the engine would be noisy though as remember this happening on the M110 engines, my 103 runs fairly quietly. Does anybody know of a site that explains clearly how to get valve clearances 100%?! I have attached a picture of a spark plug that just came out. Unfortunately the picture isn't great but the plug tips look fine however the base of the plug, bottom of the thread is blackened, its smell I cannot make out. Could be carbon or oil fouling. The valves have just been re-seated etc. so I guess it's either incorrect valve clearences or an overly rich mixture? Thanks & enjoy yourselves tomorrow night! Last edited by Brabus3.6; 31-12-2004 at 04:43 AM.