[QUOTE]Originally posted by wgfrazier
[B]courtneyg

Thanks for the thorough reply. I wish my initial post had been as complete. I failed to mention that I've checked compression, and all cylinders were 410 psi +-10 psi on a cold engine. In addition, I've checked all the glow plugs and they glowed quite red. However, I did notice that they were quite pitted, and that one or two seemed to require quite a bit more time to heat up than the others. Do you think this is significant enough to warrent replacement? One other point that I should make is that on many occasions I get blue smoke on start up, but not always. Can the presence of the oil that is creating this smoke influence combustion?

I would try new plugs first. From the other info it sounds like you might have a slight stem seal/guide issue but I have never heard of a slight amount of oil in the combustion chamber fouling a diesel's air/fuel mix sufficient to cause a vibration or miss. As you know, the glow plug's performance is critical during cold weather start ups. Any inconsistencies in the set are very likely to cause imbalances or percieved 'missfires', especially if the relay cycles off before the plug reaches its specified operating temperature. Be sure to check resistance of each plug. If you have a current measuring clamp, it would be helpful to see if one plug is 'hogging' all the current or if the 'under performing' plugs just have too high a resistance. I like using the current clamp because it takes into account the possibility of varying resistance with temperature and most closely approximates actual conditions of use over the DVM resistance check.