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Car Backfires

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L

lostdog

Freshman Member
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1980 MGB Limited Edition
I have changed the cap and roter, spark plugs, adjusted valves, checked timing and the car still backfires. It does this during shifting and when cars is turned off continues to sputter and backfire. Any advice? What do I do next? /ubbthreads/images/graemlins/confused.gif
P.S. Great site just found it today.

American Home Inspector Directory
 
Welcome to the BCF! If everything you mentioned checks out ok, then it "might" be excess carbon buildup on the tops of the pistons. I had this problem on one of my non-British cars. The car would sputter and "run-on" when turned off. It turns out the excess carbon on the tops of the pistons would glow and act to ignite the mixture at odd times and cause the car to continue to "run-on" even after the ignition was cut off. I'm sure those more knowledgable than I will have other suggestions, but when you mentioned that the car continues to sputted when turned off, my former problem came to mind (assuming you are certain the timing is ok).

Basil
 
Hi LD, What if anything has been done to the Carbs.???---Keoke
 
Basil,

Where you able to fix the problem? If so how?

Keoke, I have done nothing to the Carb. Wanted to ask around before rebuilding it. If that is my next step where do you suggest I get a rebuild kit? Thanks for your help
 
HI, Most of the usual suspects sell the kits.However, I would try reajusting the mixtures before tearing into the carbs.There are three ways to remove carbon from an engine. 1} with the engine running at about 1500-To-2000 Rpm spray brake fluid into the carbs makes a lot of smoke so do it in the country. /ubbthreads/images/graemlins/laugh.gif-2}Remove the head and clean the valves,chambers and piston tops off. 3} take the car to a Mechanic that Knows how to burn it out using a conventional welding torch and proper adapter. #2 is probably the method most people would use. Also check with others on the forum and see what the optimum spark plug is for the method you drive the car ---Fwiw---Keoke
 
Is all the anti-pollution devices still installed on the car? Check all rubber hoses for a leak as they can cause the engine to backfire. Check the timing, clean the carburator and adjust, cleans sparkplugs and fill tank with premium fuel, add a really good carb cleaner and drive at 70 mph for about an hour. If this does not improve things then you will have to rebuild the carb and start over.
 
Welcome aboard lostdog. Guess you are not so lost now. /ubbthreads/images/graemlins/grin.gif

Have heard or rather read where others have used SeaFoam. Never used it myself, but do not remember a bad review of the stuff. One word of warning, it is suppose to produce a huge white cloud of smoke. Any members every use this product? Your evaluation would be appreciated.

Let us know how you fixed the problem, lostdog.

/ubbthreads/images/graemlins/cheers.gif
 
If you don't put too much in too fast, plain old water will do the same job. This method of carbon removal has been around since engines were made. If you are in any doubt about how to do it, driving at 70 mph for an hour, as suggested, will do the job.
D
 
If you use the water method to remove carbon, spray it into the intake(s) slowly, then increase the amount going in until the engine starts to slow down. Stop and take it for a high speed spin. As with most of the advice here, do it at your own risk.
/ubbthreads/images/graemlins/cheers.gif

Guinn
 
Thank you all for your help. I will dig into it this weekend. I am going to try cleaning the carbon deposits and adjusting the carb 1st. Any tips on adjusting the carb?
I will post my results after all has been tried.
 
I'm suprised nobody asked, but what kinda of carb? Sromberg? Weber? SU's?
 
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