Tweet
I have installed new plugs, wires, cap and rotor and still have a severe low speed (and at idle) miss. All help appreciated.
-
-
Re: C3, Severe Low Speed Miss
Jack,
Short out one plug at a time and you can identify which cylinder or cylinders are missing. Then pull valve cover and check push rod, rocker arm, valve spring. If everything looks good there do a compression check.
That is a starting place.
Verle -
Re: C3, Severe Low Speed Miss
Vaccum leak, probably on 5 and 8 where the vacuum port is. Pinch off those lines and see if it goes away.Comment
-
Re: C3, Severe Low Speed Miss
When I first got my 70 it sometimes missed or sputtered at moderate acceleration. I changed the plugs, which were dirty, and it worked for a while, but the sputtering returned a few weeks later. Then I re-checked the plugs I'd just put in and they were filthy again!
I discovered that the choke was not opening enough, and the carb was getting insufficient air. I believe this resulted in incomplete combustion, which quickly fouled the plugs, which caused the misses. I bent the choke rod slightly to allow for a larger opening and thus more air, and changed the plugs again, and have had no trouble at all since.
While it sounds like your problem at low idle may be different, the choke may be something you want to check out just in case.
Good Luck, Patrick Moresi #45581Comment
-
Re: C3, Severe Low Speed Miss
I had the same issue with my '69 350/350. Turned out to be a bent plug electrode on #2. Felt like a timing or vacuum issue, but wasn't. I too had replaced all the ignition parts - plugs included. But I must have dropped the #2 plug and bent the electrode after gapping, but before install. Never hurts to re-check them.
I also had a pesky miss issue on my mid year: turned out to be two broken exhaust springs ('66 L36 427 - stock springs). Had a very noticable miss around 1500-2200 rpm, then would smooth out. Changed-out all the springs - runs like a champ.Comment
-
Re: C3, Severe Low Speed Miss
"But I must have dropped the #2 plug and bent the electrode"
While rare, it DOES happen occasionally... You can get a large piece of carbon build up in the combustion chamber flying loose and 'wack' the spark plug's electrode thus changing the air gap.
Also, on Shark cars, failure to periodically change the filter for the vac system (small white plastic disk at the intake manifold), can result in the filter element becoming SO clogged that it rips free. Of course, being in-line to the intake manifold, where do you think the filter element is going to go?
If you said into the intake and on through a combustion chamber, you get an ATTABOY award! Valves and spark plug electrodes generally DISLIKE foreign particulate matter flowing through them....Comment
Comment