The 200 I6 in my 70 Maverick has dropped a cylinder. #1 cylinder to be exact. I have replaced and double checked the points, condenser, the cap and rotor, the leads, and the plugs. All good. Yet when I pull the #1 lead off while the engine is running there is no change in the idle. I'm thinking broken valve spring or the cam lobe on the intake side has gone flat. Any other theories?
Do a compression test, or if you suspect a broken valve spring just pull the valve cover. You say no change at idle does it smooth out with the wire hooked up and more rpm? If that's the case I would suspect a bad egr valve.
No change. When I pull any other lead the engine slows down etc. When I pull #1 it run the same. On 5 cylinders, execpt it's definitely not spark related
If the #1 wire and spark plug checks out then... Compression test. If #1 is low then you know its the valves or rings. Funnel a little 40 weight oil into cylinder #1, if your compresion bumps up some then your rings need replaced. If the compression stays the same then its valve related.
Pull the plug and see if the ground strap got smashed against the center electrode...If it looks good...Swap it with one of the other plugs in the engine and see if the dead cyl followes the plug. If so, get a good plug...If not...Compression test is in order. Good luck!!!
Had a bent pushrod on a 200 once. As per other posts, compression check. Then pull the rocker cover and watch the movement of the rockers and valves. My bet will be a bad exhaust valve! Not a hard or expensive fix! One other thing to check is the soft plug at the forward end of the intake log. Rarely will this go bad, but I have seen these rust out and produce a vacuum leak.
