My 2002 Cadillac Escalade Ext 6.0 lq9 with 180000 miles has some mystery electrical issue affecting starting. 

it all started when I had an oil leak repaired, the “valley” gasket was replaced. Since then my truck randomly, it is not consistent, will not start the first try, but always starts the second try. It tries to start and even puffs a little bit out of the exhaust but won’t and you could crank it for ever. But the second try it starts up like it was brand new.

my local mechanic is baffled and spent many hours trying to fix it. At first I had low fuel pressure so we thought that was why it was starting the second try. I’ve had the fuel pump replaced. Still happening.

All my mechanic can conclude is that it is an electrical issue and that when this failed startup happens the engine doesn’t do the initial knock that it’s supposed to. I had limited time when he looked at it. He suggested to me to disconnect the knock sensors for a week and see if it starts every time. 

so my question is what could be causing this, and if I disconnect the knock sensors and it works fine will I have to get them replaced I know that it is expensive to do that. Also will disconnecting the knock sensors affect how it drives? I have to move soon and will be towing a trailer so I’d probably wait to try it after if it does affects power. 

I should add that when the oil leak was repaired their was one plug that was covered in oil that he replaced. It may possibly be the knock sensor plug. I’ll have to call and ask, could it be that what he replaced it with is faulty and is causing this issue? The truck never did this in 8 years of ownership until this valley gasket replacement.