CalG

Hello all

New guy here.

I have just been assigned "primary care giver" to a pretty sweet 1979 RX-7.
Pretty sweet, except for a consistant misfire under any load only when it's warmed up. (I get some nice smooth drives into work in the morning, but with the summer heat, the noontime drives are less than ideal)

This yellow beauty is all original with regards to the points in the distributor.
You should have heard the guy at the parts counter "Points!" You don't hear that word much anymore!" During the purchase and sale transaction, there were some "under tones" murmered about "ballast resistors(BR's) and replacement coils" while the papers were passed, so everything might not be showroom stock. I have not confirmed that the previous owner (P/O) might have changed out some components like condensers, coils or BR's, but 6.4 volts shows up at each coil positive terminal with the ignition on, but the engine not running. 8.0 volts is read if the relay just in front of the battery is energized to send that extra "jolt" of electricity. (What the heck is that relay called again ;-)) If I read the Haynes book right, this relay should power up by the "controller" above 4000 RPM while under acceleration.

The hesitation happens mostly at RPM's less than 4000, and in fact "forcing" some extra revs is a sure way to "clear things up" When those rotors get going past the problem , What a nice blast! smooth!

Leading plug color looks good, and it's timed to the "idle setting". I plan to degree the pully soon, but first things first.
Trailing plugs are black (all four are 8's)

Fresh points (.019" gap) and cleaned up plugs "seem" to make everybody happy, for a while,(60 miles) but the misfire returns. Bad Rex! Bad, Bad Rex!
Perhaps it was just cooler last Sunday afternoon. There were rainshowers.

I just picked up all the "Tune up parts" from my local neighborhood jobber, so I plan to pull the distributor and do the "rebuild" job on the bench.(No bearings however). It could be the p/o put the .5 micofarad EMF noise suppression caps on the points insted of the .27 microfarad items that are needed, or even that a 1.5 ohm coil has been swaped, and a 3 ohm unit put in it's place. I plan to check that tonight.

Question: What component or system would be most suspect considering the symptom of "under load" misfire.

The fuel pump clicks away nicely, the fuel filter is new and flows well when disconnected, and the engine runs strong at high revs, so I don't think I have a carb problem. (But there are so many "systems" on that thing!!! grrrrr.

I'm watching a 1980 Dizzy that on E-bay and might just pick it up and go that way, but, I would like to get understanding and then past the present situation.

Ideas anyone,

Anyone want to sell a working electronic dizzy complete with ignitors?


Thanks in advance from a New Guy having some fun!

Regards

CalG

Kentetsu

I don't know the details involved, but you should be able to swap that dizzy out with a newer one so that you can get rid of the points. That would be my first step, especially if you are already considering a replacement. Good luck!

CalG

Thanks for the encouragement.

The Dizzy on E-bay has days to go, and I'll be on holiday. Wish me luck!

'Didn't get to the ignition last night, The Energy Suspension Polyurethane bushings for the suspension came, so I spent the evening with sway bars and tension rods. (From Suspension Restoration http://www.suspension.com/) Shamless plug, but the gal on the phone is fun to talk to ;-)

Never-seeze and rubber grease is so hard to wash off the back side of your arms ;-)

wow! The "clanking" is gone from the front end!

The holiday week end should give some time for the electrical sluething.

I don't like driving in weekend traffic anyway.

Great list

Regards

CalG in VT

CalG

Just thinking some one might benefit from my experience.

I pulled the distributor to check play and re grease the advance plates.

What did I find? Well, some where along the way the GROUND WIRE SCREW had been "replaced" with one that didn't quite fit. It couldn't be tightened. This would provide a lousey electrical path to ground for the points.

Upon re-installation of the "rebuilt" dizzy, the engine runs sweetly all through the range with nary a hitch. Oh! I love points! (when they are working right ;-))

Cost of repair? Two sets of points from the local auto parts store, About 10 bucks! The condensers tested good.

Well, just for those who want to know.

Now I just "need" that R_B exhaust system!

Regards

Cal

Kentetsu

Congratulations man, thanks for the update!