Read my spark plug...

[theholycow]

I pulled the drivers side front spark plug to take a look at it. Anyone care to read it? I don't have enough experience reading spark plugs.

[GasSavers_Erik]

I think it looks fine- you are definitely not burning oil in that cylinder.

Do you feel that it might be misfiring? Does it look different from the rest of the plugs?

[Jay2TheRescue]

Looks pretty normal to me. You might be running a hare lean, but not too bad. No oil burning. Clean, check gap, and reinstall.

[Jay2TheRescue]

HC, are those normal AC Delco copper core plugs? If so you may want to switch to the AC Delco Platinums. You can easily get 100,000 trouble free miles out of the platinum plugs.

[theholycow]

It's definitely doing something that you might call a misfire. Sometimes with moderate throttle, sometimes with heavy throttle, it skips and bucks. Sometimes it's pretty severe. It's not consistent.

I originally thought that it was fuel starvation, as in the carb bowl is going dry (can a mechanical fuel pump get tired or does it work right until it completely fails?). After replacing some rotten vacuum hoses going to the distributor it seemed to improve (temporarily) and that made me think maybe it's NOT fuel starvation.

Additionally I think I'm missing some power and fuel economy, and it doesn't seem able to exceed ~3000 RPM.

I haven't checked the others, I just pulled that one because it was the easiest to get. Maybe I should inspect the rest.

They're basic Autolite copper plugs. I'm not worried about plugs that will last 100,000 miles. I'm not particularly confident that this engine will last that long and by the time 100,000 miles comes around they'll be seized in there pretty bad anyway.

[pgfpro]

Originally Posted by theholycow

It's definitely doing something that you might call a misfire. Sometimes with moderate throttle, sometimes with heavy throttle, it skips and bucks. Sometimes it's pretty severe. It's not consistent.

I originally thought that it was fuel starvation, as in the carb bowl is going dry (can a mechanical fuel pump get tired or does it work right until it completely fails?). After replacing some rotten vacuum hoses going to the distributor it seemed to improve (temporarily) and that made me think maybe it's NOT fuel starvation.

Additionally I think I'm missing some power and fuel economy, and it doesn't seem able to exceed ~3000 RPM.

I haven't checked the others, I just pulled that one because it was the easiest to get. Maybe I should inspect the rest.

They're basic Autolite copper plugs. I'm not worried about plugs that will last 100,000 miles. I'm not particularly confident that this engine will last that long and by the time 100,000 miles comes around they'll be seized in there pretty bad anyway.

I would pull the other plugs then. The timing bluing ring on the ground strap looks right where it needs to be at the bend. The A/F ratio ring on the porcelain can't be seen because it will be where the sun doesn't shine at the base of the thread where it meets the porcelain. So you need a spark plug light or cut the thread part off the plug to see it in full.

Heres a pic of plugs that went through my hell that I cut the threads off. LOL

[Jay2TheRescue]

Autolite copper plugs are crap. I was never able to get more than about 10,000-15,000 miles of satisfactory service out of them. At least replace them with AC Delco copper plugs. You can usually catch the Delco platinums on sale for $2-$3 each, so its not terribly expensive.

As far as your misfire, check the other plugs, but also check your plug wires for defects and make sure you don't have it miswired. An easy way to check if you have defective wires is to wait till its dark outside, remove air cleaner and idle engine. With a windex bottle full of clean water, mist the wires. If you see any spark escaping to the engine block then you need new wires.

I also recommend checking the cap & rotor. I highly recommend Niehoff replacement parts for cap, rotor, and wires. Delco Platinum for the plugs. If Niehoff is unavailable at your local parts store then buy Delco for the other parts as well.

EDIT: Its been a while since I've bought ignition parts for my Buick. Niehoff is now doing business under the brand name BWD.

[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?

[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....

[Jay2TheRescue]

I have seen where it was miswired, but the timing was far enough off that it was only noticeable only at certain RPM's. IMHO Niehoff/BWD ignition parts were just as good, if not better than OEM. Their plug wires even have nipples for the OEM distributor ring (OEM wires have not been available with nipples in many years)