Slow89Iroc-Z

Motor and car in sig. OK....disconnected the blk/tan wire. Timing on #1 was rock solid at 6 degrees and mark was steady and constant. However I move the pick up of the timing light to another wire and the mark is there and then for a bit not there and then back again. Like a miss. This happened on about 5 cylinders and the car really Idles like crap..engine shakes really bad.... If I try another wire like #8 it will be constant like number 1....Move to number 4 and it misses like described before. Wires and plugs are brand new on this motor and I rebuild the dizzy with a new pickup and ignition module myself. Gap on plugs was checked and set at .035. However the dizzy was never used in another motor and had 65K on it. Also the timing light is brand new craftsman that I used on different motors. Could this be a bad dizzy.

ZZ28ZZ

If the timing is OK with #1 wire, then it's OK.
Does the eng start missing when the inductive pick-up is placed on a plug wire, or does it miss all the time?

Slow89Iroc-Z

Misses all the time and idles like crap...shakes bad.... Only 3 cylinders fire constantly and the other 5 miss like crazy as watching the balancer. For the other cylinders I picked out a number on the balancer since I have the Street dampr and watched it and it would be there then not... So that cylinder missed..correct....what would cause all these cylinders to miss all the time?

ZZ28ZZ

Sounds like arcing inside the dizzy cap. Is the cap new? Can you see tiny little black lines inside the cap? That's a sure sign of the spark getting lost inside the cap.

Slow89Iroc-Z

new cap and rotor..brass terminals

ZZ28ZZ

Did it run OK for a while, then just start doing this?
Did you use heat sink compound on the backside of the ign module?
The reason I ask is, if no heat sink compound was used, the module would have been OK till it got good and hot, then fried itself. A fried module can do all sorts of wierd stuff.

Might wanna look inside the cap with a strong light. If moisture gets inside the dist cap, it can ruin a cap quickly.

ede

try trouble shooting it a little. make sure the tune up is good, just because parts were recently replaced doesn't make them good.

RB83L69

Twiddling the timing won't fix a broken ignition system. Put it back where it belongs, and leave it alone.

If multiple cylinders are doing the same thing, then it's not plugs or plug wires. Those could be less than ideal but they're not the cause of the problem.

Something that all cylinders share in common is defective. Cap, rotor, coil, module, maybe even the pickup coil. For that matter, it could be a bad connection in teh incoming 12V feed to the ignition system. Try another cap & rotor first; if they don't fix it, put them back on your shelf for your next tune-up. Watch the motor run in complete darkness, see if you can see arcing anywhere around the dist or coil. Take the module and coil to a parts store that can test them. In other words, do some troubleshooting.

Slow89Iroc-Z

Yea... been trouble shooting this for months already..new cap and rotor, took ignition module to the Zone and it tested good, and ohmed out pickup coil and it came back good. I pulled the dizzy and hooked up the pickup coil leads to the multimeter and set it on frequency. Slowly spun the dizzy gear in my hand and when the magnetic points lined up I would get a pulse on the multimeter however almost with every revolution there would be some that wouldnt register. The dizzy has 65K miles on it.....maybe time for a replacement.... Thinking MSD that comes ready to run with new module and pickup. Ohmed out the coil too and it came back good. Its an MSD 2 plug GM coil and there was some arching to the metal ring it sits in.......its only a few month old also.....

Vader

When you removed the pickup coil, did you closely inspect the reluctor for cracks, bending, etc? Id teh distributor shaft running true, or slightly bent? Is the switching module definitely grounded? Connections intact? Did you test/replace the filter capacitor in the base of the distributor?

Slow89Iroc-Z

vader?? filter cap??? where?? car is an 89?? I looked at the reluctor and didnt see any cracks and shaft spins true.... There is a bit of up and down movement and when installed the rotor can be turned slightly by hand even when the gear is meshed with the cam..

Vader

Not sure on an '89, but an '86 has a capacitor in the distributor base, used as a tach filter. Your's may be located elsewhere, but I'm guessing it is near the coil.

Slow89Iroc-Z

did new cap rotor, ignition module and ignition coil and no change

Slow89Iroc-Z

Well pulled dizzy again and took a beter look at the reluctor on the shaft. Turns out the magnet in it is cracked straight through like a pizza with 4 slices. All the way through. Guess I need a new dizzy.... Do you guys see any benefit in paying $300 for an MSD #8366 since I already have the coil and if this fixes the problem I will get the box, or should I just get a new one from GM for like $170. Does the MSD one come with a better ignition module???

Vader

Yup. That'll kill the pulses for sure. If the rest of the dist is O.K. (bearings good, etcetera) you can get repair parts. If the bearings are worn, you might as well get a factory replacement.

The only advantage to some aftermarkets is the roller bearing on the upper end. If you already have teh better HEI module and a good coil, there is really no advantage.

Have you priced a replacement at SDPC? They seem to have a little better price than most dealers.