I have a major problem with my Yukon. It has been going insane for the last week. It will cut off randomly, shudder, and sometimes the RPMs will drop to zero, then after 5 seconds start back up to where they were before. I ran the codes this morning and came up with a code 42, Electronic Spark Timing. What the heck is this and how do I replace it? I need to fix this, I drive this truck 35 miles to work and 35 miles back on I-40 and I-85. Can anybody help me out here? /forums/images/graemlins/1zhelp.gif Thanks!