backfiring

[larry emrick]

What does a popping exhaust note while coasting down a hill denote, and how can I remedy it on our 2.5 gas, weber carb? Otherwise starts on the touch of the key and runs beautifully.
Thanks, Larry and Pippa.

[Rob]

I had an 88 with a late model Zenith that did the same thing... turned-out to be too lean on the idel setting idle.

Cheers, Rob

[larry emrick]

Hi Rob:

It was leaned out to get it throught Air Scare; perhaps when it was reset it was not richened up enough.
Can anyone point me in the right direction to do so? Because it is running so well I am reluctant to just start poking around with a screwdriver.
Larry

[RoyP]

My 2 1/4 w/zenith does the same thing. Condition of the plugs indicate no issues with mixture. More often than not people are commenting 2 1/4 & 2.5 aren't fast enough. My recommendation is don't coast .... keep your foot in it! :-)

[ANDYD]

I always thought "popping" was unburnt fuel going through the exhaust.

I wonder if the timing of your spark is slightly delayed allowing unburnt fuel to be forced out through the exhaust.

I dont think its a carb issue, more likly distributor / spark issue....

[HeadDamage]

Popping on overrun can be a fault in the ignition system somewhere, usually a bad wire or plug. If it is this some day you might have a large boom that opens your muffler like it was a tin of beans in the fire ;) I had this happen once in an old 88 and it will get your attention!

[Greg S]

Pop-poppop-pop as you coast with foot off the throttle?

It's a Land Rover thing. Get used to it! Or fix the exhaust leak. You are getting fresh air in the system. Number one culprit in my experience is the connection between header and exhaust pipe. Could also be head to header gasket.

You could also be getting fresh air in after the carb but before the exhaust. Second choice but still possible. Carb gaskets, Intake gaskets and maybe some others.

[Greg S]

Oh! And by the way- prepared to be driven near crazy trying to eliminate these subversive leaks.

If you find a way to seal the header to exhaust pipe connection, please let me know. In 10 years of running my 109 I've not been able to seal it more than a few short minutes at a time.

One exhaust shop told me to not come back again. I was being nice and everything and even paying him by the hour to fix it, not warranty work for free. I guess he was too frustrated and gave up.

[gudjeon]

The header to exhaust leak can be a tough one. I usually remove the pipe, take a dremel with a rough bit. Use it like a die grinder and clean up the old rust and exhaust cement, etc. Once the inside of the "exhaust doughnut" is cleaned up, I put a thick smear of exhaust cement and offer it all up for assembly. I doesn't have to be pretty, just down to bare metal, same with the exhaust side. It works every time.

[Dave_F]

I always thought "popping" was unburnt fuel going through the exhaust.

I wonder if the timing of your spark is slightly delayed allowing unburnt fuel to be forced out through the exhaust.

I dont think its a carb issue, more likly distributor / spark issue....

On my 109 i used to get this as well. Put in an electronic distributor set up, set the carb up...gone!