FAST Dual sync distributor/MSD 6a/MSD blaster HVC(blue body)

Coolant sensor is front of the manifold under thermostat, ECU matches the guage. The one in the foreground is the ecu(black and white wire)
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Holy cow - I was looking all over for that piece of rubber hose sitting at the bottom of the manifold HUH -Rich

Ok, the dual sync probably rules out over heating magnets getting weak and causing a bad signal. I planned on using my Mallory distributor as a cam sensor and a homemade crank trigger to get the crank signal. The rare earth magnets I put into the damper were too small and when they got hot, I'd loose the signal. It took me a while to figure out what was happening - magnets get weaker as they get hotter who knew . I haven't yet replaced the magnets, so I'm just using the distributor for a crank signal.

I'm going to guess you've got a thermostat stuck open - either jammed with something or just failed. Is that the cause of the stumble ? IDK, but I'm guessing you will let us know !

Wedged -

He does seem to running "too cool" IMHO... and ECU's use ECT (engine coolant temp) for a LOT of control of fueling etc... So, too cold could cause him some 'errant' issues.

Thermostats don't usually fail "open" unless he has that type.. there is a type that fails open. I'm wondering if his thermostat is running within it's operating range... i.e., 175 degrees actual reading for a 180 thermostat seems within range? But I do think it's a bit cool for the application....

RICH -- Nice storage place by the way. I keep rubber hose there all the time... it keeps it soft and pliable - well - until it's been heat cycled a few times - then it can get dried up and a bit brittle. <grin>

Rich --

I'd forgotten about this - but one time I had an errant "stumble" - but it was at any time - any place... I finally found it was one of the connections at the distributor - the "clip" on the weather pack connector wasn't clipped - it looked like it was but just wasn't quite. Once fully engaged the problem went away. Also had a bad Dual Sync one time - something with the circuit board - replaced it and have had total reliability ever since. That was very early on in the Accel EFI years (something like 8 or 9 years ago at least). They used to have too small of a wire harness coming out of them (too small and too stiff too!) but they've since changed that.

I'd leave the tune alone, to me sounds like a poor connection or possible ignition issue. You can hit the wires with a quick mist of water from a spray bottle. That should atleast rule out an errant issue there. Night time usally works best to see cross-firing etc. Sometimes a cracked plug can do the same thing.

As Greg pointed out, I'd double check the connections in the distributor and injector harness. Usually a misfire or stumble should show itself in the O2 log. If your not seeing it, maybe you need to look to the opposite bank for possible issues.

Changed my plugs today and then took a peek inside the cap. Why does the inside of my distributor look like its been living below sea level. The screws to get the rotor off were actually furry, and the distributor plate completely rusted . This thing is a couple years old with about 500 miles. Im thinking the level of moisture inside the cap has to be very high. Wonder if this is causing my miss?

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Rich

Wow thats in tuff shape. That would definately cause problems. I don't know if its all of your trouble but might be big part of it.
Rich do you have a Batery disconnect on your car ? It almost looks like electrollises on a boat.

Wayne- no disconnect, but I did probe around with my DVM and theres no voltage at all on the primary side of the coil when the key is off. And there's no current draw off my battery with key off either.

The black cap in the pic that came with the fast dual sync distributor does not have a vent in it. I wonder if thats part of the problem. I just installed a new msd cap with a vent, it seems to be running well in the garage but havent had a chance to get it out. I switched sparkplugs from accel 416 to NGK FR5 , I hope the heat ranges are pretty close, I noticed the white portion is protruding out a little more than the accels. The accel spark plug also has a screw on terminal end and it always annoyed me that no matter how tight you make them they always loosen up.

Maybe the weather will be better tomorrow to take a ride and check it.

Wow buddy! That's nasty and MOST CERTAINLY would/could cause your issues!!

Glad you found that "scank" even if it wasn't the problem!! That is a problem in the making!