Where oh Where is that popping coming from?

debriga

Registered User
OK.

Help me out here before I go insane!!! 93 SC, 130,000 miles on the clock. runs TERRIFIC, pulls good vacuum and boost and gets great milage. The engine idles very smoothly, gives no hiccups when accelerating, passed emmissions with flying colors as a a real "green" car, yet it "pops" in the exhaust (yes, that read "in" the exhaust, like in the cats or resonator) without any real reason for doing so.

Sometimes the popping sounds as though it is coming from the front passenger floorboard area, other times it is from farther rearward or on the drivers side. It moves about on it's own whim, and is annoying the hell out of me. It's there during light acceleration, cruising, and deceleration. It does not seem to rear it's ugly head above about 40 MPH. It is never more prominent in any one of these aforementioned driving modes than another.

What should I do about these gremlins other than opening a salvo of 300 magnum rounds in hopes of hitting a few these little devils? The car runs absolutely great in spite of these popping noises. They don't seem to interfere with drivability or performance in the least. They are just there to screw with my mind enough to send me over the edge and into the twilight zone!!

Afterburning whithin the exhaust is not something new, but it has always run hand in hand with a performance loss in my past experiences. This time, it does not. Somebody, please save what is left of my limited sanity and stop this damned popping noise before I will it onto some other unfortunate soul!!


An SC owner doomed to hell unless someone helps!!
 
If you think it is worth following up on the noise actually being in the exhaust, you could start with the following:

  • Run the codes to see if both O2 sensors are happy
  • Hit the cats with a laser thermometer when the car is fully warmed up and check for hot spots compared to other exhaust components you can similarly scan

Have you checked the fuel mileage lately? Hear any extended fuel pump activity? Smell any raw fuel? If all else fails, you might do a compression/leak down test to check for burnt valves, etc.

Ken
 
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CAT heat shields?

Is it possible the heat shields or core of the converters are coming loose? Maybe a couple of heat shields on the unibody structure have come loose?
Maybe your engine and tranny mounts are sagging causing some misalignment?
I also second the K-member bolts/mounts- engine and tranny.

My understanding is this is a loose, impacting noise- not a misfire or malfunction in engine operation. I say crawl under and try shifting the drivetrain, and see if anything is touching.
Good luck,
jj
 
ok causes of poping
1. loose exh flange letting air in . this would make popping at let back and idle.
2. bad or dirty exh valve this would let lit flame leak past valve and egnite exh gases in tube.
3. bad cat converter a broken or chattered cat can do this noise by clanging around inside its case it can also move back in exh and clog resonator.
4. bad coil i had one that had a crack in it and it jumped across the terminal to the next terminal and caused a missfire .

or it could be SC gremlins having a party in your exh.
 
It must just be gremlins!!??

Compression tests indicate all normal (kinda excludes a burnt exhaust). Exhaust fittings and gaskets all seem sound with no leakage issues. Milage has not changed in the least, and last months emmission tests say the car is very clean. I can't detect any engine missing or misfiring, so I assume the electrical is all OK. The ECU throws no codes whatsoever, so it can't be anything major.

Now, here is another small anomaly that I have noticed. When filling up at the local Shell station, the popping is reduced by about 50% to 75% less than when I fill up at another brand. It's not gone, just significantly less! And this is repeatable as witnessed by taking on fuel at different stations and expieriencing the results as though there was a formula for it all.

The car is bone stock, this started happening all of a sudden, and my medical insurance says they will not cover my impending mental breakdown due to this situation. What am I not seeing whithin this scenario that will point to a solution.

I don't have a laser temp probe to test the cats, but if it was due to a hot spot in them, I would not think that the brand of fuel would make any differance. Also, both cats doing the same thing at the same exact time?

Not trying to put down the foregoing suggestions (they have been great as they have made me think a little more), but I am still at a loss to figure this out. Come on guys, looks like we need even more suggestions!!
 
looks like we need even more suggestions!!

I worked on one vehicle (not an SC) that had a distinct popping/snapping that seemed to be right under the front seats. By the time they gave it to me to check, the exhaust, suspension, seat mounts and u-joints had been ruled out.

I tore out the carpeting and road tested...found a 4" crack right of center in the floorboard that was hidden by insulation on the top and rust-proofing on the bottom. I drilled an 1/8" hole at each end of the crack, stuffed a thin plastic wedge in the middle and test drove - noise gone.

Body shop took it from there.

As for u-joints on our cars, I believe the front one is directly under the shifter/console. Filling the tank could drop the rear, maybe change the driveline angle and effect one or both u-joints. Load up on passengers and see what happens. Same thing could perhaps apply to either rear axle, wheel bearings, or even wheels. A cracked wheel is a scary thing to see.

Been playing Dukes 'o Hazard lately?

Ken
 
Are you useing 92 octane or above? Is your spout plug connector in its place?
I have seen cars with broken cats still pass emissions. Jack it up cold and do the fist test. Have seen alot of these cars with cracked firewalls right down the middle also. You can check under the hood for this. Any codes?
 
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