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-   -   popcorn sound on deacceleration (http://www.focusfanatics.com/forum/showthread.php?t=307006)

tigercrazy718 01-19-2013 02:43 PM

popcorn sound on deacceleration
 
so i heard this weird sound today while riding with the windows down for the 1st time in a while. while going through my complex, i was slowing down for the speed bumps with the car in 1st, and hear a sound that kind of sounded like popcorn popping. any ideas what this could be? its not very loud, so i dont think it could be backfiring but i could be totally off. could it be the sound of struts settling back down on the rear? car has 123k on it and im pretty sure the struts and shocks have never been replaced. its had a CEL on forever for a stupid rear O2 sensor but im gonna pull codes just in case

Urbanspacedude91 01-19-2013 03:30 PM

Thats normal when downshifting. If you had an exhaust it would be more noticable.

tigercrazy718 01-19-2013 03:39 PM

man they backfire that much huh? good to know. thats surprising since all my other manual cars only do that on a cold start lol

Continuous 01-22-2013 06:42 PM

Basically the reason that they back fire like this is because of the compression ratio and that they use a higher octane fuel. Basically takes more to burn so therefore when it does combust during a downshift you here it cause the engine isn't masked as much by the sound of the exhaust leaving the car.

ukfan50 01-23-2013 11:34 AM

Totally normal and love the sound!

My exhaust is all OEM BUT I have a Magnaflow CBE (with resonator), CFM HFC (the $399 one I forget if it's the street or race but it flows better than their other HFC for $349) and today ordering CFM's flex pipe.

I've loved the exhaust popping noise every since I bought my SVTF but I'm sure I'll be loving it allot more when my full exhaust set up is installed next week.

mac.mogul 01-23-2013 11:39 AM

Its exhaust over-run.

When unspent fuel hits the hot exhaust manifold it pops.

tigercrazy718 01-25-2013 09:38 AM

ah yea i forgot about the compression that makes sense. all my other cars havent had nearly as high of a compression as the focus. well thanks for clearing that up guys! every little noise on this 100k+ car makes me assume the worst haha. now to locate the sound of all the creaking and popping. im assuming bushings are worn through lol


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