My Spark Disappeared!

I've been putting a few miles on my new drivetrain in order to get everything broken in, fix a few minor leaks, and work out my well documented AOD issues so that I can get it on the dyno. I've been traveling quite a bit lately for work, so this process has taken longer than expected. Last week, I finally got it in the shop to install a fresh set of plugs, re-check the valve adjustment, install a new MSD distributor with a hardened steel gear, swap the transmission pan with a deep, finned aluminum pan, and change the oil and transmission filters and fluid with synthetic. All set to hit the dyno, right??? Nope!!! Keep in mind that the engine has run just fine all this time, but now all of a sudden it intermittantly starts breaking up badly at around 2000 rpm. It will spit, sputter, and nearly shut off for a minute or two and then clear back up until the next time. I took the car over to Carter Racing Enterprises here in Savannah where I'm having it dyno'd, and it did it's thing right there in the parking lot for them. They explained to me that MSD can stand for My Spark Disappeared. They agreed that it acts like the ignition is just breaking up for some reason. Since the distributor is new and the 6AL box is used, that seemed like the logical suspect. This weekend, I replaced the MSD box, the coil, cap, and rotor... no change and seems to be getting progressively worse. This week, I'm having the old, used MSD distributor (with the bronze gear) put back in to see if the new distributor is the problem. Anyone experienced anything like this before????

I haven't... But the dist. sounds like the culprit to me, or the parts in the Distributor...

Do you have the MSD Box in a COOL place when it's mounted?

Originally Posted by FEandGoingBroke

I haven't... But the dist. sounds like the culprit to me, or the parts in the Distributor...

Do you have the MSD Box in a COOL place when it's mounted?

Since the battery has been moved to the trunk, my MSD box is mounted on the side of the front apron where the battery used to be. There are openings in the radiator support in front of the box so that outside air flows over the box.
I'm fairly conviced that the brand new MSD distributor is the culprit also. Its the only thing left in the ignition system. When I wired in the new box I traced all of the wiring and inspected it. I even eliminated a couple of splices with the new harness.
I'm pretty sure that it is not a fuel problem because it doesn't happen all the time. And when it starts cutting out I try to keep it running by patting the gas pedal; when I do that it blows black smoke out of the exhaust pipes as it spits and sputters. This indicates to me that the gas is there but just not being ignited.
We'll get the old distributor back in it tomorrow and then we'll see if that's it. If not, it's back to square one.

Got the old distributor back in the car yesterday, and sure enough it runs just fine. Now I have to wait for them to build me another one (apparantly MSD doesn't keep any 85805's with steel gears on the shelf). Maybe this time they'll actually test it before sending it to me!
Lesson learned: Never rule out the expensive, brand new part as being the problem!!!

Looks like I spoke too soon! It seemed to be fixed but then this weekend it decided to start missing again. The thing is, its not as bad as before. With the other distributor, it had gotten where the car would even shut off. Now it will just miss a little between 2000 and 2500 rpm. You can accelerate through it, but this is the rpm where the car cruises in 4th gear which makes it very annoying. Every component of the ignition is new and I'm not sure what else would cause a miss at this rpm intermittantly, and why the new distributor would improve the problem but not cure it all together. Back to square one!

Is it truly a miss, a dead spot, or a surge?

Originally Posted by dennis111

Is it truly a miss, a dead spot, or a surge?

The best way I can describe it is it feels like the ignition is breaking up. As you accelerate normally into the 2000 - 2500 rpm range you can feel it start missing or cutting out. It feels a lot like a rev limiter. With the new distributor it would start cutting out so badly that it would even stall out sometimes. With the old distributor back in it, it won't cut out nearly that badly but it still starts missing and cutting out none the less. Now you can accelerate beyond that rpm range and it will clear up around 3000 rpm and up. But then when the car goes into 4th gear where the cruising rpm is around 2500, it will start up again. Just to complicate things further, it doesn't do it all the time. Sometimes the car runs just fine for a short trip, but then acts up again the next time out. And it doesn't seem to matter whether the engine is warm or cold for it to happen.
The changes that were made when this all started were new spark plugs, valve adjustment, and a new distributor with a steel gear. The engine never missed a beat up to that point. It seems to me that if the problem was with the valves or even a defective spark plug, it would do it all the time. And of course, why would it improve with one distributor over the other when they are the exact same distributor other than the gear??? ...My head hurts...

I suspect that you have either a bad plug (cracked porcelain?), or that spark is jumping from your plug wires. Have you tried looking under the hood at night with the lights out?--Also do it while revving the motor. I don't recommend driving in 4th gear with the hood open at night with the lights out. LOL

Were the plugs gapped? I use .045 with my MSD6AL. A plug with a broken porcelain can do weird things. I used to be able to tell if there was a broken one on our ignition scope. If you have the old plugs, you might try reinstalling them and see if the problem goes away.

Originally Posted by dennis111

I don't recommend driving in 4th gear with the hood open at night with the lights out. LOL

I don't know... I'm willing to try pretty much anything at this point!!!

Thanks for the input Dennis. I'm thinking that the plugs may be my next try. Atleast they're inexpensive!

ive had this problem before,changed all the plug wires and the miss went away.it was bloody frustrating chasing that one