scared the pee-pee out me...HUGE backfire on the highway!

[konish]

Fellas,
Driving along at about 80 mph, trailing throttle to slow for some construction. All of the sudden I notice my tach drops to 0, and all the guages stop working as if someone had shut off the ignition. Anyway about 1-2 seconds later car comes back to life, followed by a HUGE BANG almost simultaneously. I looked in the rear biew mirror just in time to see a big, black puff of smoke coming out of the exhaust pipe. At about 65-70 mph I was surprised at how loud the backfire was. Car ran great after that, although it does seem a bit louder and idles a tad bit faster. I was running my A/C for the first time this year just to see how it performed and the oil temp was solid at 200 with good pressure. Now, I've been banging my head trying to figure this out:
1. I figure the backfire was due to the ignition cut out much like a rev limiting rotor works and the the backfire was due to the ignition of fuel-rich exhaust gas when it mixed with the atmosphere.
2. Permatune gremlin?
3. I checked my distributor lead wire...looks fresh and solid.
4. War weather knocked a bunck of carbon loose from the combustion chamber momentarily hampering normal ignition, which then cleared itself. I did run the motor pretty hard getting on the freeway and this is the first time in months the car has seen oil temps above 180-190.

Thoughts? Car is an 83 SC, permatune CDI, fresh plugs, 190,000 miles, 91 octane fuel, semi-fresh cap and rotor, good wires (ie no light show at night) thanks!

R/
Dustin

[Zeke]

The backfire was a result of ignition when the power came back on. The new tone in the muffler is because you rearranged the innards.

[Dantilla]

Wow. What a cheap way to get a sport muffler! Congrats!

[Emission]

Originally posted by konish

3. I checked my distributor lead wire...looks fresh and solid.

Smart... that was my issue last month.

[JMPRO]

If your gauges all went off then i would think it was a complete power failure not just an ignition problem.
Jerry

[competentone]

Originally posted by JMPRO
If your gauges all went off then i would think it was a complete power failure not just an ignition problem.
Jerry

Good thought; check the battery connections and grounds.

[howiee]

Could it be the ignition switch?
If the contacts in the switch are getting old it could cause this to happen. I had a Honda that started that way. I couldn't figure out what it was. Eventually when it would die on me I would have to turn the ignition switch off and back on,then it would work. I took the switch apart and changed the rear spring portion and never had the problem again.

Anybody seen this with their P-car?

[Rot 911]

We used to do the "big bang" in our cars in my younger days. Get going about 40 miles an hour cut off the ignition, coast a bit, then turn the ignition back on!

[RickM]

Originally posted by konish
...... scared the pee-pee out me........

I looked in the rear biew mirror just in time to see a big, black puff of smoke coming out of the exhaust pipe. At about 65-70 mph I was surprised at how loud the backfire was. Car ran great after thatR/
Dustin

All pipes cleared. Mission accomplised.

[konish]

Fellas,
Thanks. I kinda figured if I had a total electrical failure (ie a bad ground or battery) that would explin the loss of gauges. However I never considered the ignition switch. I'll keep an eye on it and if it happens again, I'll clean all the grounds and check the battery. If it happens after that, I'll have a look at the ignition switch...I figure cheap and easy before hard and expensive will be my guide in finding the problem. Also, I had a sneaking suspicion that the muffler had liberated itself of a bunch of packed in crap, but its nice to get some confirmation. Thanks for the input.
R/
Dustin

[targa911S]

Permatune.....mine did the same thing. tach drops to zero, then comes back on ...bang! Just like we used to do with dads car when we were kids. Use that thing as a paperweight. Get a Bosch box or borrow one from your tuner, hook it up, and see if it happens again. Or go to an MSD, although I have no experience with them (disclaimer)

[Craig]

Dustin,
My 77 used to do the exact same thing, sometimes more than once during a drive. It was as if I had shut the key off and turned it back on. Never did figure out what it was, although I suspected it was a ground problem because it started happening after it had been painted. I figured there was some dust from the process of sanding and painting affecting some of the electrical connections. Checking the ignition switch never occured to me, sounds like a good first place to check.
It does not happen any more because (fortunately or unfortunately, you choose...) my 2.7 bit the dust because the chain sprocket on the intermediate shaft decided to shear its teeth. This would cause of a complete rebuild of the motor to fix, so I upgraded to a 3.0 to save (a little) bucks. Fortunately, now I have a 3.0. Unfortunately it was bucks that could have been saved and used elsewhere.
Good luck on tracking it down.
Craig
77 911s w/3.0