Gentlemen,
I'm having some problems tracking this down. When I accelerate hard or get up to a certain RPM (about 3000) at cruising, I get popping coming out of my exhaust & a huge lack in power. The engine has never stalled, but I can't go any faster in that gear due to the misfiring. I've done almost everything that I can think of short of checking the timing chain & replacing the carburetor. Here's what I've done so far:
Changed coil + ballast resistor + ignition wires/wire to distributor Changed fuel filter + replaced all fuel lines Changed fuel pump Changed points + condenser Changed plugs + plug wires (plugs gapped at .035) Changed cap + rotor Changed vacuum advance (this was confirmed bad & made a huge difference)
The initial timing is 6 degrees BTDC & the dwell angle is about 31. I get about 16hg of steady vacuum at idle & about 7psi of fuel pressure at idle. The idle & even light acceleration is perfect, which makes me think it's not a timing chain issue, but I don't know enough about what the symptoms of a slipped chain would be to make that call. When the engine is at TDC of piston 1's compression stroke, the rotor lines up perfectly with cylinder 1's plug wire, which also makes me thing it's not necessarily a timing chain issue. Since I have changed the plugs & tried to further diagnose the problem, my plugs have turned black. This along with the popping in the exhaust obviously mean my mixture is either too rich, or something is going haywire with the timing & causing the fuel to not burn at higher RPM. One thing worth noting, is that I have not changed the plugs since they have been fouled since I replaced the faulty vacuum advance. I didn't know if this would make a difference or not & didn't want to risk fouling a new set while troubleshooting. I can literally get flames to shoot out of my exhaust if I abuse it enough. This happens on both sides & I have dual exhaust, leading me to think it's not a valve issue, unless I'm really unlucky & have a problem on both sides of the engine.
The jeep is a recreational vehicle of sorts, used primarily to climb up & down sand dunes. The symptoms all occured when my fuel pump died about 2 years ago. After I replaced the pump, the engine started doing this. I've since replaced it again to rule that out with no change. I've also rebuilt the carburetor, but it was the first time I ever did such a thing, so it's quite possible I missed something. The accelerator pump works fine, the idle mixture screws are set very lean (since I think the mixture is too rich for some reason), the power valve has been replaced & I even checked it again last week & I can see spray coming out of the booster venturi when I rev the engine (it does this whether I'm moving or not). Another thing I noticed is that when the engine is cold, if I hold my hand in front of the exhaust, it sprays black fluid on me at idle. It's not a lot, but I noticed it when it was sprayed on my leg one day. It has no smell to it other than stinky exhaust, so I don't really know what this is. My coolant level has not changed noticeably, so I wouldn't think it to be a water leak, but I can't say with certainty.
Here are the basics: 1972 Jeep CJ5 AMC 304 Aftermarket parts: Edlebrock peformer intake Holley 600cfm 4-bbl carb Edlebrock shorty headers
Thanks for any help you guys can give on this. I'm at a loss & don't know what to do next.
-Matt