exhaust backfire AFTER cutting off engine.
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Joined: Mar 2013
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exhaust backfire AFTER cutting off engine.
76 300ci I6 w/c6 trans (all stock)
i was told when purchasing the truck sometimes it backfires after being cut off...didnt do it for the first few times, now it is sometimes, not all the time. ill drive it (usually a decent distance) and when i stop and cut the engine, about 3 secs later POW! its exhaust because the guy told me the muffler has a hole from it, i looked under the truck, OHHH YEAH shes split open! checked the timing, my buddy set it just a little advance, couple degrees. starts and runs fine. have no clue wat else it could be. i googled and found other ppl having the issue (all vehicles) and said it could be a valve sticking. also i read where someone said let it idle a minute or so after stopping and see if it does it. i tried that for about 1 min and cut and it seemed it wasnt as loud. like i said, its not all the time. but it does happen. any advice would be great! dont wanna put a new muffler on to just have that bust in a couple months!
i was told when purchasing the truck sometimes it backfires after being cut off...didnt do it for the first few times, now it is sometimes, not all the time. ill drive it (usually a decent distance) and when i stop and cut the engine, about 3 secs later POW! its exhaust because the guy told me the muffler has a hole from it, i looked under the truck, OHHH YEAH shes split open! checked the timing, my buddy set it just a little advance, couple degrees. starts and runs fine. have no clue wat else it could be. i googled and found other ppl having the issue (all vehicles) and said it could be a valve sticking. also i read where someone said let it idle a minute or so after stopping and see if it does it. i tried that for about 1 min and cut and it seemed it wasnt as loud. like i said, its not all the time. but it does happen. any advice would be great! dont wanna put a new muffler on to just have that bust in a couple months!
Senior User
Joined: Feb 2013
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From: Idaho
timing should be 8-10 degrees with the vacuum advance unplugged from the distributer and hose plugged. that could be some of it. could be your valves out of adjustment. and or fouled/dirty valves. check your spark plugs...
Senior User
Joined: Feb 2013
Posts: 266
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From: Idaho
remove the vacuum hose from distributer and plug it then check your timing. it should be 8-10 degrees...sorry if it didnt make sense. Dont take off your vaccuum advance....just the hose. Then check the timing.
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Joined: Mar 2006
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From: B.C. Canada
Sounds like way too much fuel in the exhaust. As kids we used to turn the key off rolling down the road. Turn it back on a few seconds later and BAM! If it runs fine I doubt it could be timing to make it that bad.
Maybe letting it idle for a minute burns off the extra fuel. I'd be checking the carb. If float level is too high could be dumping fuel in the manifold when you brake to a stop.
Maybe letting it idle for a minute burns off the extra fuel. I'd be checking the carb. If float level is too high could be dumping fuel in the manifold when you brake to a stop.
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Joined: Mar 2006
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From: B.C. Canada
Yeah, you should check carb adjustments. Timing too though. Make sure your choke is coming completely off when it warms up. Idle speed is correct. To check the float level you'll have to take the top of the carb off. I think those motors came with a Carter carb. You're going to need a book of some kind with specs for those settings. Preferably a factory manual, but if not, a Chilton or Haynes. Preferably Chilton. Had problems with Haynes, but that's all you can seem to find these days. Maybe while you've got the carb apart, take it right off and do a zip kit rebuild. Not too difficult. Just follow the directions exactly. You'll have to get the carb. number to get the correct kit. Hopefully the tag is still on it or it's stamped on the carb somewhere.
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Senior User
Joined: Mar 2006
Posts: 110
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From: B.C. Canada
One other thing to try first is what Wilcam47 mentioned about taking the vacuum line from the carb to the advance on the distributor off and plugging it at the carb. Try driving it like that and see if it still backfires. Pretty sure that engine should have the vacuum coming off a timed port on the carb and not the base of it.
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