I have a 1998 chevy silverado pickup that is running great; no misses, no check engine light. However in the last few months if the engine is running, I am unable to use the garage door opening (hand held). I have two different manufactures of the openers (a liftmaster, and genie) both are circa 1998. They have worked well for years with the truck runnings. With the engine running, if I put the remote next to the opener it works fine.
The alternator was been disconnected and it is not the root cause of the problem.