Hey guys....please comment on this one....changed spark plugs in July....car ran perfect yesterday and today....then I heard a very faint backfire which my car has never done..'73 2.0...maybe ten in total over ten minutes....then on freeway whoosh!! no power and lots of noise, but not metal on metal noise....more of an exhaust whooshing sound. So I pull over to inspect and find my #4 spark wiggling so I tighten it up and problem seems to have been fixed......HOWEVER.....there is still a faint backfire here and there. I did not push the engine on the way home and have not checked the other plugs for looseness. This morning was the coldest one of the season so far...low 50's....any chance the weather let the plug come loose? Any thoughts will be greatly appreciated....thank you!
gg

Hey Greg,
I think the timeserts are the issue, with the loose plugs.
The back fire could be a MPS issue. The first back fire could cause a crack in the diaphragm.
Check to see if it holds vacuum and how long.

ps: my car has been Dr. Jeckell and Mr. Hyde.

I don't want to read to much into the issue but my engine problem started with a slight back fire and resulted in a dropped intake valve seat. I also had a loose plug on the same cylinder. I hope your case is different.
Brian

Me too....
gg

I would do a valve adjustment to make sure the valves have not tightened up. It did to me once and I did get a backfire. It blew off a vacuum line.