Popping on Deceleration

[Jcon]

I've got an '81 SC with about 55,000 miles. Major service completed 650 miles ago. I started noticing a couple of weeks ago that when I'm slowing down especially from higher RPMs I get a load exhaust popping. It's getting progressively more frequent. Also my cold idle has dropped to 250 - 500 RPM. It's fine when the engine gets hot though at around 750-800 RPm.

What's causing the popping and should I be concerned.


Thanks

Jeff C
81 SC

[needlevalve]

First thing to check when popping on decel is a leak or pinholes in your exhaust. Popping on decel is usually a result of cold air entering the muffler and mixing with the hot air causing an explosion.

The easiest way to check this is to swap your exhaust with one that you know is good.

This explanation doesn't however explain your drop in idle, if they are corelated.



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Matt Macpherson
1975 911 S
nvalve@yahoo.com