Here's a good one
Thread Starter
Instructor
Joined: May 2009
Posts: 180
Likes: 1
From: Prairieville Louisiana
Here's a good one
Why is my #2 cylinder not firing all the time? new parts from module to the plugs. Same compression as all other cylinders. can hear some sputtering out exhaust on that bank. Can a valve be sticking, burnt or a bad lifter??
Melting Slicks
Joined: May 2003
Posts: 2,076
Likes: 281
From: Dyersburg TN
you say the compression is the same (I assume that also means good). check the inside of the distributor cap and see if there is a line going between terminals. This is a sign that the spark is not going to the right plug at the right time. What does the plug on that cyl look like if you remove it?
Thread Starter
Instructor
Joined: May 2009
Posts: 180
Likes: 1
From: Prairieville Louisiana
Plug is dirty, wet. The others are light brown as they should be. I am kinda leaning towards the valve spring or was wondering about a bad lifter. Dont hear of too many burnt valves often. The cap is new and i did look at the terminals. A mechanic had it on one of those old Sun diagnostic machines and said it all looks good to him.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
Plug is dirty, wet. The others are light brown as they should be. I am kinda leaning towards the valve spring or was wondering about a bad lifter. Dont hear of too many burnt valves often. The cap is new and i did look at the terminals. A mechanic had it on one of those old Sun diagnostic machines and said it all looks good to him.
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Brett Foote
Team Owner
Joined: Jan 2006
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From: Crossville TN
Bad plug...bad wire...spark signal being shorted somewhere. Swap plugs with another cylinder and swap wires with a different cylinder. Run it a bit and see which cylinder has a problem then. (Don't be surprised if you no longer have a problem, either.)
Thread Starter
Instructor
Joined: May 2009
Posts: 180
Likes: 1
From: Prairieville Louisiana
Held engine at 1/4 throttle and slowly dumped a qt. of Marvel Mystery oil down its throat. Engine is running much better but still has a small miss. Will change out #2 plug next.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
does it misfire under load? yes do the above suggestions, but if you have good compression then who knows.. Idle circuit on the carb may be mis adjusted if it runs fine under load... a little misfire is OK.. if your mechanic had it on a scope and saw nothing then do a little idle tuning then forget about it... did you check for vacumm leak?
Thread Starter
Instructor
Joined: May 2009
Posts: 180
Likes: 1
From: Prairieville Louisiana
Vacuum is 17hg. Slight 1/2in. swing both ways every 15 seconds or so. Carb. is new rebuild. It was doing this before i changed carbs. Heavy load is ok, the main miss is at steady speeds and a slow increase in speed. its ok when you drop your foot in it. At steady speed, it felt like it was dropping a cylinder. I'm assuming a valve sticking now. Will do more fuel additives to see if it helps out. Compression is so-so 85lbs cranking. low by my standards.
Melting Slicks
Joined: May 2003
Posts: 2,076
Likes: 281
From: Dyersburg TN
old school
we had a trick when a single plug was messing up or hunting for which was messing up. With engine running pull wire at distributor and move it back to make the spark jump (which makes it hotter). Sometimes it will clear the problem. The engine should stumble as you move it to far away. If not, that cyl is not hitting.
P.S. hold the wire tight, a loose grip will knock the crap out of you
P.S. hold the wire tight, a loose grip will knock the crap out of you