Question about 1989 Cadillac Fleetwood

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1989 FLEETWOOD 4.5 Engine will run smoothly for some time, then will cough and fart and back fire. put trani in nuetral it will clear it self out. It runs smooth in nuetral, Put it back in drive it starts to run rough again. Changed Dist. Cap, Rotor, coil, spark plugs, spark plug wires (one at a time to keep order). Now it really Backfires, Blew the Muffler right off ! Let it sit for a month, had to put a battery charger on to start it, started fine ran smooth, idled up to operating temp. No backfires but i fear putting it in gear and maybe blowing up another muffler. Can Anyone Help Figure this Out!! Is there a vacuum switch on the transmission that could make it Backfire ??? Thanks in Advance for Your help !!

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Hi and welcome to FixYa!

Transmission has nothing to do with this. I'm suspecting that there's an engine problem. Any noticeable white smoke on the tail pipe when it runs? This back fires are caused by a worn out piston rings and worn out valve seals. If the problem still persists I strongly suggest that you get your engine rebuilded to resolve the problem.

Hope this helps and thank you for using FixYa! Have a good one!

Posted on Dec 29, 2010


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