coil or ignition box?

[70challengerrt]

My challenger is missing when driving, when idling its fine and runs great except under throtle. I switched to electoric ignition and used a mopar adapter with the 4 prong ballist. I was also thinking about switching coils to an accel but didn't know if it would work here are the specs (SUPER STOCK; PRIMARY RESIST 1.2 OHMS SECONDARY
8.9 K OHMS; TURN RATIO 100:1; MAX VOLTAGE 42000V ) or will the extra resistance screw up my tach and distributer?  Any help and suggetions would help out! Thanks!

[FY1 RT SE]

The only thing that an Accel coil will do is lighten you wallet up a little more.  Have you tested your coil to see if it is bad?

[Bullitt-]

test your coil?    I see posts to the effect that you can get the ignition box too far away & loose power, did you lengthen the wires?
      
Mopar Ignition Coil Test      
This testing procedure is valid for just about any automotive coil. Using an ohmmeter, check the resistance between the side terminals of the coil. Do this with all fo the wires to the coil disconnected. You should see 0.75 to 0.81 ohm of resistance. Then check the resistance between either side terminal and the center high tension terminal. The reading should be 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate that the coil is defective.       
      
      
      

[ShelbyDogg]

First things first. Dumb questions, I know, Did it run okay before you changed to electronic ignition? Did you set the timing? Are you sure that your wires are installed in the correct order. Is the coil getting it's power through the balast resistor in the RUN position.       When you say "missing" when you drive, do hear backfiring through the carb, popping through the exhaust, or does it just not have any power and sound kinda normal.. Need more info.

[Bullitt-]

We had a Dakota V6 that started and idled fine, even took off ok under light acceleration but if you came to a hill or gave it a lot a gas it started  stumbling w/no power. It took the shop 3 tries to figure out that there was something inside the distributor not working(I figure the advance mech.) Did you add a pickup for your electronic conversion that might be interfering with something? Or possibly a used unknown distributor that might have problems? 

[70challengerrt]

OK here is up to date. I did not have a chance to fire the motor before I changed ignition because I came in pieces like the car. I am running all stock mopar ignition except the coil is Excel. I changed the distributer, coil, cap, rotor, wires, plugs, ballast resistor with new stuff. I did a compression test and high cylinder is 140psi low was 128psi. I turned the motor over with the valve covers off the make sure the rockers were moving a decent to see if the cam was junk (it was fine). Do you think this could be the electronic ignition box? I changed the carb to a edelbrock 750 which was off my GTO and was running good so it should be getting gas. As for the feel and sound of the car: It has power at full throttle and when you don't get to far into the gas (its the middle of the throttle) it popped through the exhaust once or twice but that was it. Thanks for all the help.

[Bullitt-]

 I'm bout out of ideas, I never had a problem w/electronics  few ideas but before you do anything based on this lets hear from others.   fuel pump, low fuel pressure, clogged fuel filter. bad fuel, cam out of time/stretched timing chain, stopped up exhaust, something makes me want to say coil wired backward, engine ground strap,
most of these I have 1st or 2nd hand expieriece with having to solve poor performance problems. \

I feel yer pain
 

[70challengerrt]

New fuel pump, exhaust is new, fuel filters are new. The coil has the positive to the stock wire harness for power and the cylinder style condenser, the negative is to the eletronic ignition harness which includes the ballist resistor and the tach wire. Is this right?

[Bullitt-]

i'm looking in my manual now will get back in a couple  Mine is a '73 though

[Bullitt-]

dis is what I see on mine & the book says BR (brown?) to pos. BK/Y (black w/yellow) to neg. the book does not show tach. in this illus. but on mine it goes to neg. I'll keep looking but I don't see how that could cause a prob. if your tack is working.

[70challengerrt]

I hooked up my tach once and at idle (700 rpms) it reads about 5500 rpms and moves with the engine reving up but reads way to high. I posted it on the board and was told the tach was shot and should be restored or replaced. The car was sitting in the garage and ran fine so I figured they were right it wasn't until I drove it down the road that the throttle problem was found.

[Bullitt-]

can't find any wiring info on Tach. but I just had a brain tremmor. try disconnecting your tach. once many moons ago I heard of a problem being caused by a bad aftermarket tach. Who knows. What ya got ta loose

[70challengerrt]

Thanks for all the help Bullitt!

[Bullitt-]

hope you get her runnin good. everybodys in the chat room now se ya

[Bullitt-]

another idea. I've never had this kind of issue but it is worth looking into. Vacum Advance , Assume new Dist. Good parts. What about the Vacum? Leaky/stopped up/kinked hose. I also read about different ports on the Carb. or Manifold are better that others at delivering accurate vacum for the purpose. Pull off the vac hose at the source w/the engine running. Suck on the tube a little & see what happens. if little or no change the hose could be the prob. test source. find a port w/more vac.