engine misfire

[stranman]

Just a quick basic question
My truck started to miss a couple of weeks ago.
So I put new cap and rotor in.
Points looked good, I would have put new points in but the ones I got from 'American Military Parts' did not seemed to fit correctly, but that is another story.

Truck still is missing from time to time.
New plugs where put in a several months ago, but I do not drive the truck much.

What are the usual culprits?

I did not pull the plugs to check yet, but the engine seems to run pretty well, no smoke. Although it seems to run a little rich based on the smell.

Please keep in mind guys, I am just a backyard mechanic, so my questions may seem lame.

[george walker]

Im sure someone here can supply the napa number for the points and condenser so you have the right ones in there, pull the plugs an look at them they should be fairly clean an dry a wet plug shows one that isnt firing. ck the gap (030) a incorrect gap can def cause some performance prob. if all the plugs look goood you might be looking at a failing coil or a fuel prob. ck the mixture adj. the coil isnt really practical to test so replacement is the way to see but leave it as a last resort so you dont spend money you dont have to.

[wrecker]

Often a miss that sounds irregular is really always there. Maybe when you idle down it's more pronounced? I would not rule out irregular compression from cylinder to cylinder. Also, a weak valve spring can cause one cylinder to act a little off. A compression tester will help diagnose these things and costs about 30 dollars. One might be a good investment to check your engine.

[george walker]

a vac gauge is good too it real cheap and will show a weak or bad valve, smooth vac around 18-22 ok, wildly fluctuating needle shows bad valve, low vac can show exh restriction or jumped timing chain (belt)

[george walker]

just so you have it the napa number for the points: cs725a and condenser al869

[stranman]

thanks for the info guys. Will pick up points and a condenser.
Will look to pick up a compression and or vacuum tester this weekend.

The 1st set of plugs I pulled seemed fouled, what usually causes that?
I gapped the plugs when I put the new ones in a few months back.
I do have a replacement coil I picked up on ebay that I can throw in as a test.

[wrecker]

The fouled plugs are due to weak ignition, bad air fuel ratio (rich or lean), compression/vacuum problems (valve train usually or piston rings) Basically, the plugs aren't going to tell you exactly so you'll have to snoop a little further. You can find it fairly easily with the right tools.

[george walker]

from having wet plugs and smelling rich id say to look at the carb mixture adj and if its flooding while driving

[Captain Jack]

On either side of the points and condenser are 2 small metal tabs held on by small screws, they hold the plate that the condenser and points are on, and slide into the wall housing of the distributor, making sure that when you hit a bump, the plate doesn’t bounce around. Mine had shifted and I was having the same problem. As soon as I made sure they were holding the plate down correctly, it fixed the problem. Captain Jack

[george walker]

you can also add electronic ignition to these the pertronix 'ignitor' is a simple kit that fits entirely under the cap www.pertronix.com