Read my spark plug...

[theholycow]

Originally Posted by Erik

Pull the plug wires one at a time while it is running to verify that the idle decreases (meaning that cylinder was firing before you stopped it)

It would be weird if I was running on 4 or 5 cylinders this whole time. I'll try that for sure.

[Jay2TheRescue]

Here's a good cure for purchasing Autolite:

From the makers of the infamous "Orange Can Of Death" comes Autolite spark plugs! If they think they can cut corners and use hot melt glue to manufacture an oil filter, what makes you think they can make a quality spark plug? Besides, even with your 30,000 mile history with them in the truck, the OEM Platinums will go 100,000 and beyond.

Find the OEM plugs on sale, and in the long run not only do you save money, but the pain of changing the plugs. Especially the #6 cylinder. That's a true pain on old Buicks as the A/C unit protruding from the firewall makes it darn near impossible to get a socket wrench in there and be able to move. I had a stubby extension about an inch or 2 long. It was the only way I ever found to do it and not take hours to get the last plug changed.

[add|ct]

Originally Posted by Jay2TheRescue

Here's a good cure for purchasing Autolite:

From the makers of the infamous "Orange Can Of Death" comes Autolite spark plugs! If they think they can cut corners and use hot melt glue to manufacture an oil filter, what makes you think they can make a quality spark plug? Besides, even with your 30,000 mile history with them in the truck, the OEM Platinums will go 100,000 and beyond.

Find the OEM plugs on sale, and in the long run not only do you save money, but the pain of changing the plugs. Especially the #6 cylinder. That's a true pain on old Buicks as the A/C unit protruding from the firewall makes it darn near impossible to get a socket wrench in there and be able to move. I had a stubby extension about an inch or 2 long. It was the only way I ever found to do it and not take hours to get the last plug changed.

I couldn't tell where you went from sounding like a lame salesman to making great points, good post!

[Jay2TheRescue]

Originally Posted by add|ct

I couldn't tell where you went from sounding like a lame salesman to making great points, good post!

Its a gift!

[pgfpro]

Originally Posted by theholycow

I guess I'll pull the rest, and maybe I'll sacrifice one or two so I can autopsy like that. What's the best way to cut the thread off? My instinct is a cutoff wheel.

The cheap Autolites worked great for 30,000+ miles in my truck but maybe the Buick doesn't like them.

I think my cheap distributor cap may have been BWD. Anyway it might be time to invest in some better quality ignition parts, but I would just rather diagnose first before throwing parts at it.

If I had miswired the spark plugs (definitely possible, I lost my labels while changing them and had to do it from a chart) wouldn't it consistently run terribly?

The way I do it at the track is to chuck the plug into a drill and then put the drill in a vice or make a way to secure it. I then use a hack-saw to cut the thread part off with the drill at a low speed.

If you got your wires crossed it would run like crap. Unless as a example on a GM with the firing order 18436572 5 and 7 get crossed. Its just a very light miss.

[GasSavers_Erik]

If you can't get over 3000 rpms, I would check the distributor advance weights/mechanism to make sure it's free (you could just attach a timing light and rev it up to verify this).

It could also be an issue with your secondary barrel of your carb- if the butterfly is vacuum operated, check the diaphragm and the hoses for leaks. It would be tougher to check the secondary jets for clogs without removing the carb...

Severe bucking would indicate fuel starvation- you might put a T on the fuel line to the carb and see how much extra fuel it can pump into a gas can while the engine is running (clamp the line with some vice grips to provide a little resistance so it can build some pressure and keep the carb full).

If it can't deliver much extra fuel- look at the filters and pump. Hopefully it isn't a clogged screen in the tank....

[theholycow]

Since it's turned into troubleshooting my problems I moved the thread to Troubleshooting & Repair.

Anyway, there's a vacuum diaphragm attached to the distributor. I don't know what it's called. Do they fail? I imagine that if they do fail, they can be flaky rather than just always dead. Is there a way to test it?

Then there's this thing. One line goes to the aforementioned diaphragm, one goes to the manifold, and one goes to the carburetor. This is the thing whose rotten lines I replaced (I also removed its rotten boot). Should I investigate failure in this? (Lower left of photo, yellowed plastic thing)

[GasSavers_Erik]

The diaphragm on the distributor advances the ignition timing under certain conditions- most of the time they operate on manifold vacuum and keep the timing advanced at idle but some vehicles use venturi vacuum or even ported vacuum. I think manifold vacuum is best from an economy standpoint.

They do fail first with a small leak, then with a big leak- just connect a vacuum pump and see if the diaphragm holds vacuum (it should). If it holds vacuum, then test the mechanism it by applying vacuum while you have the timing light hooked up- it should advance the timing.

The yellow plastic thing looks like a one way valve- like would be found on a brake booster hose. Hmm- or maybe it is part of the charcoal canister system for collecting fuel vapors from the carb or delivering them to teh carb to be burned.

[Jay2TheRescue]

I think it is part of the vapor recovery system.

[theholycow]

Jay, you make a good pitch against Autolite plugs.

The yellow plastic thing is not part of evap. It connects to the manifold, the carb, and the distributor's vacuum diaphragm. It is definitely part of the vacuum ignition advance.