For the past year or more, my Yale lift has had a miss that comes and goes almost on a daily basis. I've had 5 different mechanics look at it and none seem to be able to figure out what is causing the problem. All have been able to make it go away for a short period of time (2 mos) by replacing the plugs / cap / rotor (in the past 12 mos I have put 4 sets on). I think all this is doing is "masking" an underlying issue...I don't know what that issue is, but that is my belief. The particulars of the problem are these:

Some mornings the truck starts and runs fine all day without any issues.

Some mornings the truck starts and runs fine most of the day - you shut it off - start it back and it has the miss. The truck is started multiple times a day - it comes and goes at times.

Some mornings the truck immediately has the miss and it never clears up throughout the day.

Some mornings the truck immediately has the miss - you shut if off - start it back and the miss is gone.

The miss is so bad at times that it doesn't have enough power to pick anything up.

Here's a little info about the truck:

SN: E813V04514D

V6 GM Engine - Electronic - LPG

It has been hooked up to a diagnostic computer on several occasions but never has any trouble codes available.

This may or may not be pertinent, but it seems to always have a lot of condensation coming from the exhaust. Never low on water - so I would presume no gasket issue...

Any help would be greatly appreciated.

Thanks in advance!