Aarrrgh!! Early S Problem won't go away! (LONG)

[Kevin G.]

I have done everything I can think of, as well as all the suggestions you good people have made and I still can't find and fix the problem with my poor baby!

I still have this nasty-a$$ bucking and backfiring from 3000 to 3600 rpms. I have:

Replaced a burned up rotor and the cap for good measure.
Pulled the dizzy, cleaned, oiled, replaced and reset optical trigger and timing.
Swapped in the original black bosch for the blue one - no change. Swapped in a new MSD unit to match the CD with no change either.
Swapped a known good cd unit for the MSD 6A this evening and still no joy.

This is something that happened suddenly while I was out of town for a few days, and my son was driving the car. He swears that it was fine one day, and acting up the next. I am inclined to believe him, and I can't think of anything he could have done that would create a problem over a 600 rpm range only.

The problem seems to be there after the car warms up, if it exists when cold, I can't tell, but I don't run it hard at all until it is warm. At that point, it accelerates to 3K smoothly, bucks and jackrabbits to 3600, then smooths out and pulls well to near redline. I do seem to feel some reluctance in the high 6K range, where before I could easily hit the rev limiter, but that may just be me looking for something that isn't there.

The bucking is worse the more load that is put on the motor - more pronounced accelerating uphill than downhill, harder acceleration, etc.

That pretty much rules out the entire ignition system, other than the optical trigger (all it does is send impulses to the CD, rpms shouldn't matter), the plug wires (somewhat new Magnecores) and plugs (spec Bosch platinums, but still with factory gap). Again the plugs and wires should cause a rpm specific problem.

One last thing - I could not completely dissassemble the dizzy, the drive gear is held in with a hard steel pin that I could not budge, and I sure didn't want to hit it too hard and damage the shaft or drive gear. Even so, lateral play in the shaft was nonexistant. There was some top-to-bottom play, but I didn't think that would be a problem. I hosed the internals down pretty good with laquer thinner and made sure that the weights moved freely and the springs were operating. Everything seemed ok to my very limited ability to tell.

Sorry for the long dissertation, but I wanted to provide as full a recap as I could.

So - can somebody please help me?

Please, please, please???

Help me Obi-Wan, you're my last hope!

Gasp

death rattle.....

[Early_S_Man]

Kevin,

Any idea how much vertical play there was on the central shaft with respect to the housing? Could it be as much as 1 - 2 mm (0.040" - 0.080") or more? Play in that range would cause quite a bit of timing 'scatter' ... as the drive gear and shaft jump up and down on the crank gear!

I suggest finding an old timer at a shop that has a Sun distributor machine ... and have him check out your distriutor and eliminate the vertical play. Get a plot of the advance curve.

[CamB]

I hate to be the one to suggest this, but have you religiously gone through the MFI "Check, Measure, Adjust" setup procedure?

(edit) Just had flicker in the back of my mind and remembered Matt Smith suggested you try richening it slightly to see if it fixed the prob - have you tried yet?

Cam

[NYSCAR]

I'm with early S man, try to see if you can find somebody with a compatible temp distributor willing to lend it to you for a test.

Brad

[Kevin G.]

Thanks, Warren.

The gap was nowhere near that wide, I had my valve adjustment feeler gauge handy, and it was too thick for the gap. It was just about wide enough to make an audible click.

I'll check with local PCA members to see if there are any local repair shops that regularly work on older cars. If they don't have the equipment, they can likely tell me where to go.

Cam -

Yeah, I am about to dust off the old check, measure, adjust book. I will admit I have been avoiding fiddling with the MFI - it took me soooo long to get it running well. I recall Matt's suggestion, but did not follow through as I am already on the slightly rich side.

Brad - That's a great idea! I'll have to look around to see if someone has a spare 2.2S dizzy I can borrow. It would probably be a good idea for me to try and find a spare for myself as well, since rebuilt units are NLA at Pelican.

Are there any Ventura area Pelicanites that has a spare dizzy I can try?

Time to go to work! Thanks for the help, guys.