Have a strange miss.

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J

jeryst

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I have a 73 Challenger 4-speed with a stock 360. Lately, it has developed a miss/backfire.

It doesnt do anything when accelerating. And it doesnt do anything when backing off. But after I let off the gas to back off, and then just touch the gas to start accelerating again, it stumbles and backfires (out the back). Once I give it gas, it smooths right out.

I've had the car for about 5 years, and it always ran good, so I never tuned it or replaced anything, although it would do this same thing on very rare occasions. But now it is doing it almost all of the time. Most of the time it is in storage, and doesnt get driven very often. I put fuel stabilizer in the tank and always use high test gas. I also use engine oil with sufficient ZDDP.

Does it sound like fuel or electrical? Time for a full tune-up? Timing need adjusted? Carb need rebuilt?

I'd like some opinions before I start replacing stuff.
 
Pull the plugs and look at them. Reading plugs tells a great story. My guess is if you haven't tuned it up for 5 yrs. it's time. The older stuff didn't run nearly as long as new cars do on a tune up.

Does it sound like fuel or electrical? Time for a full tune-up? Timing need adjusted? Carb need rebuilt?
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Out of all the things you listed in the above quote the only one I can most likely rule out is the timing needing adjusted. Why you ask? Once timing is set it changes very little. Not generally enough to cause this problem. Unless the dist. hold down is loose of course. It never hurts to check the timing though. Any of the other things could easily be the problem but I'd start at reading the plugs first. You might pull them out and find them burned to a crisp cause their so old.
 
These cars were designed to have regular maintenance. You can't drive them for 5 years and do nothing. If they are new to you (meaning you didn't grow up with carbureted cars or anything older than late 80s) then you should know it will need the usual tune up stuff, cap, rotor, wires, plugs, fuel filter, plus the carb should be rebuilt and the whole thing tuned when that's all done. Better than factory parts will help it last some, especially good 8mm plug wires... but there are always limits and high powered ignitions will eat plugs, caps and rotors faster. Most cars back in the day would have been in for basic services that would have adjusted things and rebuilt/cleaned the carb at least once a year, and i recommend rebuilding any aftermarket carb at least once every two years if once a year is too much. It sounds like it needs just the basic maintenance.
 
I've had it for 5 years, but I havent even driven it 1000 miles. I had not driven it this year at all until the other day, when I noticed the problem. So it became much worse from sitting for a year.
 
Maybe the carb is gummed up now from gas sitting?Also check 3 5 and 7 blug wires?Maybe touching each other?
 
moper said:
These cars were designed to have regular maintenance. You can't drive them for 5 years and do nothing. If they are new to you (meaning you didn't grow up with carbureted cars or anything older than late 80s) then you should know it will need the usual tune up stuff, cap, rotor, wires, plugs, fuel filter, plus the carb should be rebuilt and the whole thing tuned when that's all done. Better than factory parts will help it last some, especially good 8mm plug wires... but there are always limits and high powered ignitions will eat plugs, caps and rotors faster. Most cars back in the day would have been in for basic services that would have adjusted things and rebuilt/cleaned the carb at least once a year, and i recommend rebuilding any aftermarket carb at least once every two years if once a year is too much. It sounds like it needs just the basic maintenance.
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LOL SO true.

I think since they started all this EFI crap a lot of people have forgotten things like maintenance since with an EFI controlled car, some people NEVER change the plugs over the entire time they own the car.

Back in the dya you had points, plugs, adjusting the carb, and all kinds of stuff popping up in between. These babies need love.
 
pettybludart said:
Maybe the carb is gummed up now from gas sitting?Also check 3 5 and 7 blug wires?Maybe touching each other?
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Anything I have had sitting that long...I prime the oil system, rebuild the carb for giggles, and change the plugs, check cap/rotor.

You can't go wrong.
 
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