Does your car have factory A/C? If it doesn its common for a leak around the connection to the vacuum canister.
are the deposits that form on the plug when you take it out to clean it, a dry sooty black stuff or an wet oily black goo? is there smoke coming our of your tail pipe when the car idles or accelerates? is there a puff of smoke right when you start the car? is there excesive black soot on the end of the tail pipe? i cant see how a vacuum leak would cause the cylinder to run rich. it would go lean. that would not cause a spark plug to foul out. i really suspect that you have bad rings on that cylinder. its possible that you may have a bad valve guide but i really doubt it. the other possibility is that the intake gasket on that cylinder may have a leak on the bottom side allowing it to suck up oil. i would do a cylinder leak down test on every cylinder. this would show if the rings were your problem. if it passes the leak down test then i would pull the intake manifold and look down the intake port of cylinder #8 and see if its oily. if its oily and the rest are not then that where the problem is. at this point you need to check the surface that he gasket touches for straightness on both the intake manifold and the cylinder head.
I have seen even new gaskets split and leak drawing oil from the lifter valley considering your only having this issue on one cylinder its worth checking
Yeah, it has factory A/C. I thought it might be leaking there too so I tried disconnecting the vacuum canister and plugging the port on the tree but still had the same results as before. I don't think I'm getting a leak there. I tried the same thing on the transmission vac line too (while parked only, obviously) and still no change for the better.
That sounds like the vacuum advance may be leaking. You can check it with a hand vacuum pump. (Don't have one? They're not expensive.) Just attach it to the hose going to the vacuum advance, pump up some vacuum and see if it holds. If the vacuum advance has two hoses, be sure you don't have them reversed. Wouldn't account for all your symptoms but might be part of your problems.
I haven't seen any smoke on startup, idle or when accelerating. My tailpipe has always been blackish at the exit so it's hard for me to tell anything from that. The stuff on the plug is more of a dry, sooty black stuff. The rebuilder has referred me to an old-school guy he knows to see if the rebuild was faulty and see if he can find the problem. If he's not helpful or wants too much $$$, I'll try the leakdown/compression test next. I'm just trying to troubleshoot as much as I can for free without having to disassemble the motor....this is my daily driver and I feel bad leaving the wife at home with 4 little ones and no vehicle. I may have to just cheat it for a while with a hotter plug, but I hate to put a band-aid on something that may lead to a bigger problem down the road.
I'll check this. I have the vac from the carb to the port on the front of the advance and I have the rear port plugged. I haven't had any problems with this in the past but please let me know if I need the rear port to be used. I don't think I've mentioned it but I also have some light throttle surging. It's not really bad, but it is noticeable.
Can't help you on the two vacuum advance ports. Never had one of those. Someone that knows will chime in.
Best way to check for this? I've looked down the throat of the carb while idling but can't really tell much from this. Both squirters from the accelerator pump seem to be working fine. I haven't seen any leaks on the outside of the carb it's on nice and tight. I plan on opening up the carb to see if there's some trash inside restricting flow and also check the float level. Any ideas why my fuel filter looks empty sometimes but the car never dies? Fuel pump? Common issue but not critical?
Probably going way out of bounds of what your looking for. But might check fuel flow. Make sure there is no blockages or leaks. Look at the rubber hose under the driver floor. I have heard it can crack and suck air. It's a cheap replacement anyway so may as well just change it for peace of mind. If you have a sock on the end of your pick up check it and maybe just replace it. Gonna have to replace the gasket too if you open that can o worms haha. Good luck and hope it's an easy fix whatever your fixing..
Not out of bounds at all. I'm looking into anything/everything I can. I appreciate your input. I didn't even think of the line under the car. It's old and needs to be replaced. I haven't noticed any fuel leaks under the car but not sure what behavior any cracks there may have.
Just replaced the PCV hose which was badly cracked/aged. This barely, and I mean barely, helped smooth out my idle, but at idle it still has the intermitten miss. You know, you would think that the guys who put the motor back in the car would have replaced all the hoses and cheap stuff like that. Don't even get me started on how bad those guys were.
Well, running out of all the free, do-it-yourself tests that everyone's mentioned and still no luck. All that is left that I can think of is a compression/leak-down test on the cylinders, which I don't have the equipment for. Knowing MY luck, it will be the worst case scenario.....or it will be something stupid like a hairline crack in the carb spacer or something. Any other last-ditch advice before I have to just admit defeat and take the car in to a shop (hopefully a more reputable shop this time)? I still can't believe how badly the shop that that handled my rebuild f'ed this up. Wouldn't surprise me if they didn't pour sugar in the tank to try to earn another visit from me. Crooks.
Yes, buy a compression tester (not free but its not expensive either) and test all the cylinders. Get one with a rubber hose and fitting to screw into the spark plug hole. If you do have a serious problem, that might be enough evidence to take it back for warrantee work rather than diagnostic work you have to pay for. Even if you don't want to take it back to the "crooks", it might tell you that a tear down is necessary. Pull all the plugs so the engine will spin freely on the starter when you check each cylinder. If you're getting good compression, or even 80 PSI, I wouldn't think leaking valves or rings are causing your misfires.
