1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Horrible backfire when I accelerate too fast/floor the car.

Old 03-14-05, 06:06 PM
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Horrible backfire when I accelerate too fast/floor the car.

Hello, this problem started almost immediately after doing a sparkplug change. I decided to test out FC sparkplugs in my car. I recently switched backed to the stock FB sparkplugs and the problem still persists. I want to sell my car so I can afford a sports bike, so I would to take care of this problem as soon as possible. Any help is greatly appreciated as I would rather save my money and do the work myself.

An exact description of the problem follows: I take my car up to 3.5k before I can floor it as a result of my Mikuni dual 45mm barrel. If I immediately floor it at that RPM the car will rev up to approximately 4.5-5k RPM and then let out a horrible flaming backfire. If I immediately let up on the gas that is all that happens and it drops back to idle and then seems to run fine. However, if I continue to floor the car it will backfire repeatedly and at great speed resulting in a god awful sound and a complete lack of power. I am driving the car daily as if I do not attempt to accelerate fast there is no sign of any problems and it runs just as it always has.

I am presently thinking it might have something to do with the timing but I really do not know.

Thank you for you time,
Adam
Old 03-14-05, 08:08 PM
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Sounds like you got the plug wires mixed up when you were changing out the plugs. Could also be the timing, do you have a timing light?

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Old 03-14-05, 09:11 PM
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My 7 shoots flames also but I have run it hard to 5 or 6k then down shift and let it go down to 4 1/2k. I like it though. Mine been doing it ever since I fixed the fuel injectors.
Old 03-14-05, 10:37 PM
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Unfortunately it is not the plug wires. They are correctly placed as that was one of my initial ideas. I do not have a timing light, but I can easily come by one.

When functioning I take my FB to 7.5k on a daily basis. What is happening to my car is not a healthy function nor is it the standard rotary engine backfire and it is by no means desirable.

Last edited by deimox; 03-14-05 at 10:39 PM. Reason: grammar
Old 03-14-05, 10:51 PM
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you know what? my car did the same thing, check your fuel filter, does ur car throw a flame out, or just backfire and buck?
Old 03-14-05, 11:25 PM
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Make sure your distributor cap is not misaligned. Sometimes it can be bumped off center and cause timing issues...

Also, how old are the plug wires? Recent movements could have opened up or exposed cracks in them. This could cause the spark to "jump" to another wire causing crossfire.

Run the engine in the dark and move all of the wires around watching for any sparking.

Good luck...
Old 03-15-05, 02:33 PM
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My car does throw a flame out when it backfires like that. I'll check my fuel filter this afternoon. I put a new one in mid/late summer so I wouldn't think that it should be too bad.

I checked the distributor cap it appears to be aligned, if alignment is determined by the retention clips. My wires are pretty new and look to be in good condition but I'll check them out tonight.

Thanks for the tips,
Adam
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