popping through exhaust SOLVED

[1970440RT]

     Hey guys, a new problem for this year.  I just pulled the cars out for summer and one of them now has a "popping " through the exhaust after about 3000 rpm.  The motor is a 440 with Mopar electronic ignition, new last summer and have already changed the ignition box last fall to correct a different problem.  The popping happens in park as well as under load.  The more rpms go up, the worse and louder it gets.  I had a problem with this motor this winter, when I would start it to get the juices flowing, it would intermittently pop through the exhaust at idle.  I attributed this to a burnt plug wire which had come into contact with the headers and would arc to the header pipe.  A change of wires and plugs this spring cured the idle pop but now I have this problem.  The timing is at 18 degrees at an 850 rpm idle and 36 degrees at 2900 rpm all in with no vacuum advance.  Anyone else have a similar problem and can point me in the right direction?

[dodge freak]

Had a poping noise one time and it was a small hole in the header pipe, but not sure if thats your problem.

[Chryco Psycho]

a leaking gasket will do the same , make sure the exhuast is fully sealed

[1970440RT]

a leaking gasket will do the same , make sure the exhuast is fully sealed

Never thought of that.  The exhaust is good to go at idle but maybe creating a leak at high rpms.  It also seems to be worse if the car is fully warmed up or has been run for a while.  At this point I can't rule anything out, I'll try one thing at a time starting with the exhaust until it goes away.

[Chryco Psycho]

if the exhuast leaks it can draw in oxygen & cause hot unburnt fuel in the exhaust to ignite

[firefighter3931]

It could be going lean at higher rpm. Check your float levels and look at the plugs.

Ron

[myk]

Maybe it's a bad muffler?

[1970440RT]

Did not get a chance to crank down the header bolts yet but the 1 and 5 plugs are all a light tan color.  I was sitting at a cruise all day and all I had was a spark plug socket, no wrenches.  Doh.  On the way home, the high rpm miss was still there. 

[1970440RT]

Got another chance to work on the problem again.  I put on new header gaskets with new bolts.  The old ones that came out looked good.  I took it out for a drive and the pop was still there.  At idle now it seems to be barely there at all but under load, same as it ever was.  This seems to point to fuel delivery.  I changed the fuel filter and the pop is still there.  How can I tell if it is starving for fuel while on the road driving? 

Anyone else experience these symptoms?

[1970440RT]

The carb is an Edelbrock 750.  ( sorry Chryc )  The floats are set per the manual.

[Chryco Psycho]

check the plugs probably white , if so up jet it

[greenpigs]

How old is the gas?

I would get some of the gas "cleaner" they sell at auto store and top it off with the highest octane gas available.  Might not be it but a cheap possible fix and how old are the filters and are they paper elements?
On mine on year the filter dried out and broke down so when it got gas again I had little pieces of the filter mixed with the fuel. It popped under they load like your talking about but in park\neutral ran fine.

[RECHRGD]

My 440 did the same thing when the coil was going bad.  The coil failed completely within 50 niles or so.  If you've put alot of miles on it with no change it's probably something else, but worth a look anyway.  Bob

[1970440RT]

How old is the gas?

I would get some of the gas "cleaner" they sell at auto store and top it off with the highest octane gas available.  Might not be it but a cheap possible fix and how old are the filters and are they paper elements?
On mine on year the filter dried out and broke down so when it got gas again I had little pieces of the filter mixed with the fuel. It popped under they load like your talking about but in park\neutral ran fine.

This tank of fuel is new this spring but I've already gone through about 3/4 of it so its about time for a fill up.  I would like to just try one thing at a time to correct this problem and find out what the heck is causing it.  I have a bad habit of throwing many solutions at a problem without sometimes knowing exactly what the root is.   I also just changed the fuel filter.  I'll read the plugs again and see if they have changed color.  Next on the list to swap out is the coil and fuel pump. 

[greenpigs]

Thats fine, but are you going to test them before replacing or do you have backups already?

I used to throw money at problems but after spending time on this site\old one I check things before replacing.

I would consult a Chilton manual on how to test a coil.

One thing at a time is how to do it & I agree but don't get in a hurry.

[1970440RT]

Thats fine, but are you going to test them before replacing or do you have backups already?

I used to throw money at problems but after spending time on this site\old one I check things before replacing.

I would consult a Chilton manual on how to test a coil.

One thing at a time is how to do it & I agree but don't get in a hurry.

Thanks for the input.  I have 3 other running big blocks that I know are good, so swapping parts is pretty easy for me.  Now if it would quit raining, I could get some of this done...

[1970440RT]

    I can rule out fuel and timing.  Last night I filled it up with new 94 octane and cruised on the highway for about 30 miles.  Popping was still there.  I got back and pulled some plugs.  They are all tan to light greyish.  I then tried advancing and retarding the timing & driving a mile or so with each adjustment.  No improvement.  Next up...coil.  Hopefully tonight. 

Edit: rule out contaminated fuel

[greenpigs]

Not to be anal, but I would have pulled all the plugs. I know a few suck getting to but ya never know.

[1970440RT]

You are right, I'm getting lazy.  1 and 5 are easiest to get to so that is what got pulled.   I'll do the rest tonight before I run it again.

[mikepmcs]

this sounds like an ignition problem to me.  i realize that has been covered above but just wanted to throw my
oh yeah and i wanna know what fixes it too.
v/r
Mike

[1970440RT]

More info:
 
     I inspected all the plugs, all pretty close in color-light tan.

     I changed the coil over from my Challenger.  No luck, miss still there.

     Next I changed the ignition ECU.  No change.

     The only good news is that while driving and changing how much throttle I give it, I learned that if I mash it to the floor, the breaking up starts right at 3000 rpm and at about half throttle the motor will wind up to 3500 rpm before it starts to miss.  This tells me almost for sure that it is fuel delivery.  Time to swap out the fuel pump and inspect the rod and go from there.

     The only other problem is that the car was sold this past weekend ( just the car, I get to keep the motor ) and I have to yank the motor out this Saturday.  I'd love to fix this problem before I pull this motor out.

[konigcharger]

     

[histoy]

My friend has a 528 Hemi in his car.  It was running poorly so he asked me to look at it.  It was popping like crazy thru the exhaust at all speeds.  It seemed to have good spark and plenty of fuel.  I pulled the distributor cap and found that the center spring contact on the rotor was bent out of shape, and the cap had carbon tracking all around the center terminal.  I cleaned the cap and replaced the rotor, and the engine ran like a Hemi again.  You might want to check yours.   Also make sure all the plug wires are inserted all the way into the cap so they make good contact.  Good luck!

[1970440RT]

     Thanks for the input histoy.  When I first started having this problem, the first thing I checked was the reluctor gap and rotor.  All that looked good.  I had a problem on another car that had a slightly cracked cap and gave me fits trying to figure out what was going on.  That was fresh in my memory so that is where I started.

    I decided to hold off on pulling the motor out of the car to try and fix this problem.  I swapped the fuel pump out with three I had on the shelf.  Here are the smash your face against the wall results:

-fuel pump # 1: A brand new in the box Carter high volume mechanical pump from Summit.  At idle, that fuel pump was pegging the needle on the regulator and pushing fuel through the carb gasket and past the hose clamps!!!   Regulator could not control the pressure, the inlet side of reg and connections at the pump were leaking like crazy.   ( this pump was a replacement for one that was leaking from the gasket on the housing, also brand new ).  I did not take the car for a test drive.

-fuel pump # 2: Slightly used stock replacement pump from Napa.  No pressure whatsoever.  The car started and sucked the bowls dry and shut off.  I tried to prime the lines and get something, no go.  I threw the pump away.

-fuel pump # 3: well used stock pump off a core motor I had rebuilt.  Got fuel to the carb and she fired.  Good to go for the test drive, breaking up now starts at 2500 rpm not the previous 3000rpm.   

    I was extremely ticked that the fuel pumps were garbage but I did narrow the problem down so I guess that is the silver lining.

    Anybody know of a good quality high volume mechanical pump?

[firefighter3931]

I've used the Carter 6psi "street" pump on many engines...never a problem. Check your fuel pump pushrod and make sure it hasn't worn down. There is an acess plug below the fuel pump....remove it, slide the pushrod out and measure it. The rod is supposed to be 3.25in long.

What is your timing set at ? Base timing at idle and total ? What rpm is the total coming in ? Are you running vacuum advance ?

Does the engine break up in neutral....or only when driving (under load) ?

Ron