Re: Mystifying miss  
Re: Mystifying miss -- Wes Notovitz Post Reply Top of thread Maverick Message Board
Posted by: Wes Notovitz ®
2001/10/28, 11:28:23
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:Ok, fellow wrenchheads...see if you can help me with this one. I have a 250cid in my Stallion with a bit over 69000 miles on it. It's got new plugs, cap, rotor, wires, and a new carb. The timing has been checked. Compression is just over 110lbs. on the front two cylinders and about 105 on the rest. It starts crisply and has power. There is an annoying miss which is very noticeable at the exhaust as well as with the general engine sound. The plugs still look good and the wires are secure. The compression test was done just before I got on here. All vacuum lines are new and connected securely. The miss is still there even when the engine speed is increased. I'm stumped! I've checked everything over and over and I still can't find the culprit. Before I have to cheat and pay a mechanic (dread!), anybody have any ideas where to go with this????


I already checked for leaks at the exhaust & intake manifolds..none. The EGR valve is bad and blocked off. The carb spacer gasket is new as the carb is new (Holley rebuild of the Carter YFA). The car still starts crisply without stalling and the valve train makes little or no noise when running at idle or under load. When I had the valve cover off to replace the gasket, there was no sludge or heavy deposits visible around or near the rocker arms and pushrods. The miss improved significantly when I replaced a plug. The plug was at cylinder #1 and did not look bad when pulled. I put in Autolite plugs (46), and I'm considering switching brands if these are going to be a problem. I was always partial to Bosch. Right now, the worst thing it is doing is hesitating when you hit the gas. The idle could be smoother, but, my experience is that I've seen few straight 6 bangers that idle perfectly smooth especially with past neglect. Both of our late model Jeep Cherokees with straight 6s do not idle perfectly smooth and they are very far from neglected. I haven't done a vacuum measurement yet.I guess I'll have to get out the Mityvac and do that soon.


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