Some of you may remember my earlier posts about a '90 300E with a 3.0L SOHC engine miss. The miss was intermittant at first but then became permanent. We found that Cyl #3 was dead, no compression, Cyls no 5 and 6 were weak as well. We removed the head and #3 had a large chip out of a valve, and 5 and 6 showed signs of blow by in the intake side. So I had a valve job done by a reputable local crank and head shop. New valves, seats, guides and seals were installed.

We just got the head back on, and low and behold a miss is still there. All cyls now show 185 to 195 lbs compression - including #3. However #3 still appears to be the problem - remove the plug wire and the idle is not affected. The cyl has spark, compression, not sure about fuel - the plug seems to be wet, but only slightly and the plug has no discernable color to read. All other plugs are burning perfect light tan.

I don't even know where to start....I'm thinking that the valves may not be adjusted correctly.

This is what I know for a fact:
The head has been rebuilt - all new parts except springs
The problem cyl is still #3
#3 has spark
Plugs, wires,dist cap and rotor are all new.
There are no vac leaks - I checked every connection
The timing gear,chain,orientation were all marked and the gear was removed from the cam with the chainin place. Tension was kept on the chain/gear until reassembly - it could not have jumped a tooth
There is good oil pressure
Temps are normal
No indication of coolant leakage or burning.
When I installed the oil spray bar, the bar seated in the supply tube but only the two end bolts lined up, the center bolt did not line up with a tapped hole in the rocker assy below it, so I assume two rocker assys were switched in error. I don't think this would be an issue though, since the oiler is seated in the supply tube and the valves were all adjusted by the head shop after the valve job was done.

This is what I am not sure of:
That the head shop checked each spring against specs.
That the head shop installed the rockers in exactly the order I removed them, although I had them laid out in order. They did apparently take the time to mark them each with positional stampings, so I assume they refected how I had them laid out, but there was the issue stated above.
Cyl #3 appears to be getting fuel as the plug is slightly wet, but I may be misreading this, it could be it should be much wetter.


Any ideas what is going on here? Any experienced help would be greatly appreciated.....

Andy

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Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey