Missfire

Okay, I plugged the vacuum line going to the AAP, and it made no difference.

The fuel cutoff solenoid has power with Ignition ON position. I disconnected it and it didn't really make much of a difference, but it made the exhaust smell much worse. Like a sharp burning smell that stings the nose.

I replaced my fuel filter too, old one was nasty, but it made no difference either.

And heres the black shit coming out of the pipe. The small dark patch is the freshest as I moved my truck back a foot.


I also ran it out of a gas can, to see if there where any issues between the tank and carb, but that also didn't make any difference.

I'm trying to find a video camera to use so I can better record whats actually happening.

have you checked your timing. i have a truck here at my shop it was havin problems like what you have been talkin about an we finally got a timing light and determinied that it has jumped time. that may be your problem. check your timing with a light to see what you come up with if you cant tell take the bolt out of the distiributor and turn it until it starts to run better if it does and you cant put the bolt back into the slot then you have jumped time

The timing is fine. I have checked it several times.

I think the cat might be clogged from the bad fuel, causing too much back pressure for it to flow at low RPMs. I'm going to test it out tomorrow after class, since I have to leave in about 30 minutes for my night class tonight.

Seth, maybe it just needs a good high speed blast to clean things out, It still may have some over rich carb problem thats getting overlooked. I gave my best shot with no hands on, which can be hard sometimes.
Just so you know your not alone, I have had a few carb issues myself.
I did a few mods on my rig this winter, can't ever leave well enough alone, upped the blower boost, definately felt that in the seat of the pants, swapped the 2bbl carb for a 4bbl, then in the 30's degree weather started having some carb icing issues, the carb sits so far to the side it doesn't get much of any engine heat, top that off with the funcitional hood scopp blasting more cold air under the hood, and the carb height, had to raise it nearly 4 inches to clear the blower, kinda acts like a tunnel ram with lots of surface area under the carb to cool, so it would ice up and crap out going down the road, I removed the K&N filter I had on it and did a little creative air cleaner plumbing and came up with my winter version air filter, works like a charm now, in fact I might be able to run it in the summer too by just rotating the heat shield so it gets cooler air from the hood scoop, we'll see how that works out. I never claimed I wanted fuel economy

That is an immaculate engine bay. My lord. Lol.

I already tried a good high speed run. Did about 80 on the freeway, still having the same issues. I am going to remove the cat and see if ti does anything.

It runs better with the exhaust disconnected (and a lot louder). And I can get it down to 1100 RPM without it wanting to die, but if I let off the gas pedal and it goes to idle it still drops too low, and gets rough. Then it stumbles a bit when I press the gas pedal again. It still seems like its running rich. But it doesn't make sense. The carb is rebuilt again, all cleaned out, and thats all I can do. These carbs aren't tunable. It only has a fast idle screw.

I don't know what to do at this point. It seems like I've tried everything.

why not switch out the carb for something less "smog friendly" until your next mandatory check? in other words, procrastinate until you have time to screw with it, plus you get a more fun carb for now.

I thought about it. And I talked to the smog guy I go to, and he said as long as it passes at the pipe he doesn't care. He told me most of my ignition stuff is illegal anyways. The only thing keeping me from that, is the cost. I don't want to pay $300 for a carb I will use for maybe 6 months or so before swapping to EFI.

I have been bouncing this around all day trying to come up with some idea to help you out on this deal, I,m assuming the ignition deal is OK, miss is gone, good compression, good fire to all cylinders, cam lobes are good, fuel system is cleaned and fresh gas, new fuel filter, timing is OK, Its apparently a over rich condition thats causing the problem.
You said you rebuilt the carb, to what extent, soaked out, blew out, new kit installed? Thinking of the things that would cause an over rich condition, carb has some crud plugging 1 or more passages inside, main and primary jets reversed in the carb, choke not opening, float level too high, stuck or not seating needle and seat, AAP diaphram pinched and not sealing. Those are some I can think of, vacuum leaks will make them run ratty but normally they run lean from sucking air, around carb base, carb base to main body, throttle shafts, or hoses.
When cold does it start relatively easy? how about after its warmed up, if running and shut it off how does it react if trying to start back up, when you took it out and drove it does it blow black smoke out the exhaust, rich fuel if so, blue indicates oil, white, antifreeze, don't wanna even go there
You have a California version carb if I remember right, has all the miles of plumbing, the air mixture screw at the base is capped off, some of those you can pry the cap off and the screw is under there to manually adjust, they are just preset for Ca. emissions, and with the header, ignition upgrade a little fine tuning wouldn't hurt if so.
Someday we'll figure this out or rebuild your truck in the process of trying to. Damn, and I just sold a weber carb and Offy intake a few weeks ago I had sitting in the garage for a 20R I had no use for.

Seth, on your distributor does it have the double diaphram type advance? The reason I ask is that when Nook mention the weber and offy combo it was one of the problems I had when I put my motor back together. I had the wrong diaphram connected, caused the carb to be overly rich and wouldn't run for squat.

Also has your fuel tank ever been resealed that you know of? The smell that it has does it smell like burnt hair or burnt walnut?? I had a problem years ago with my 'cuda, sounds very similar to your situation. I rebuilt those carbs several time, swapped fuel filters, lines etc. I finally dropped the tank and poured the contents into a bucket and it was the most foul thing I had ever experianced. I still get a whiff of it whenever it rains because like a dumbass I poured int on some fence post to kill weeds. That was 5yrs ago, LOL. It turns out that the previous owner had some pin holes in the tank and sealed it up, over time the stuff breaks down into this thick nasty shit and it will eventually clog everything up. I ditched the tank, put new ines and rebuilt the carbs again and I haven't had a problem since.


oh yeah, have you tried using any seafoam?? that stuff does wonders.