My truck when idling has this "popping" sound coming out of the exhaust. Is this a mal-adjusted carb or a carb that is needing rebuilt? This is a 1979 F-250 4x4 with the 400 and 4 speed manual. I don't know exactly what carb it is. It is a 2-bbl motorcraft. Which I assume is the stock carb but not sure. It does run real strong though. I think it is suffering a bit in the mileage area. Even though economy and these trucks don't often reside in the same sentence. Any help would be greatly appreciated...thanks.

 

I'm no expert, but if you hear a "popping" sound coming from the exhaust, that would lead me to believe that you've got an exhaust leak. Is the noise coming from near the engine? Maybe it's a blown exhaust manifold gasket. Maybe a bad exhaust joint somewhere.

Fish

 

I just hear it coming out of the end of the exhaust. This had headers and glass packs. It appears to be professionally installed. It was on the truck when I bought it. It seems to run really strong to be much of a carburation problem...I have had plenty of vehicles with bad carburetor problems. Hell my 1975 F-250 carburetor caught on fire once!!

 

Start with a vacuum gauge and see how steady it is. Try pulling plug wires one at a time (insulated plug wire puller) and see what changes. If you find one cylinder where nothing changes, there is a problem. Might take a compression check to determine what the problem is.

 

Popping in the exhaust means something is detonating in the exhaust. Or at least at the wrong time in the engine.

Is the exhaust true duals (no crossover between the sides)? If it is, does the pop only come from one side?

How loud is the pop?

Is the pop regularly timed (rhythmic, equally spaced, as in a problem that occurs in one cylinder every time it fires)? Or is it random?

Does it happen when the engine is cold, warm, idling, in gear stopped, driving?

Where exactly is the pop coming from along the truck?

Is there a pressure jump or drop at the tailpipe associated witht he pop?

Need way more info to even theorize on the problem, but I doubt it's a problem with the exhaust system.

AleX

 

It is a true dual exhaust with headers and glass packs.
The popping noise isnt real loud, maybe as loud as a champagne cork...give or take a little.
I will have to listen to it next time to determine which side it is coming from if it isnt both sides.
The pop is definetely random.
I have only noticed the pop when it is at idle and warmed up.
I just hear the pop at the tailpipe...again I will have to listen more carefully next time.

 

I had the same exact issue with my 390
Worn throttle shaft on the motorcraft 2bbl carb was causing a vacuum leak. Carb rebuild with Shaft bushing fixed the problem

Lonnie

 

I was thinking if it was something simple and cheap I would try to fix it, otherwise I will deal with it. It isnt that bad (just annoying more than anything else) and I will be putting in a new motor this summer. If it is something that a carb rebuild would fix I would be willing to do that as the kits are pretty cheap. If it is something down in the motor itself then no way...I can deal with it until the new motor goes in. Thanks to all for your replies, like always your help is appreciated very much.