Metallic Banging

[V8BoatBuilder]

Never thought I'd be starting a thread here - but I need some help.

The 1997 V8 Mountaineer has developed a "metallic banging" noise. It sounds as though someone is hitting the exhaust pipe with a hammer, or as though metal was expanding/contacting from heat. The noise is intermittiant (of coure), and happens on startup (while cranking), during idling, and the time inbetween noises increases with rpm. Sometimes it'll go 30 seconds between bangs, othertimes it'll go 2 seconds. I haven't taken it out on the road, only listened to it in the driveway.

Also, when it bangs, there is a momentery pause is the exhuast gas pulses coming from the tailpipe.

Any thoughts?
-Exhaust system - could a baffle in the muffler be loose, or some catalyst? What does that sound like? How can I test?

-Misfire - I don't think it's misfiring, but what would that sound like?

-Other?

I know sounds are the worst problem to diagnose over the net, but I don't want to drive it, incase its something with the engine internals.

Thanks,
Aaron

 

[410Fortune]

first check all the fluids.
are you sure its from the exhaust?

If it was a misfire you would notice a problem while driving, does it have any driveability problems or is it just a noise?

Do you have ramps?

visual shakedown is your best bet at this point, look for anything loose, try to narrow down your search.

 

[V8BoatBuilder]

I had the truck off the road for the last week, with the battery unplugged. I redid the ignition system among other things. I haven't taken it out on the road yet, I don't want to rev the engine a lot/put strain on it until I figure out more of what's going on.

I'm going to pull all the plugs... go from there. It's odd that the exhaust from the tailpipe stops momentarily when the bang/pop occurs, then resumes. The exhuast smell/color seem normal at this point. It's pretty cold here!

My next question is: could a fault in the ignition system cause this? I ask, because when I put the truck in gear (drive or reverse) the RPMs drop substantially, and the truck stutters. Though this may be a non-issue, the PCM hasn't relearned the correct parameters.

 

[V8BoatBuilder]

Just a quick update for those following, I pulled the plugs and the #5 cyl plug was totally black. All others were normal. I have a feeling I just didn't seat the plug boot wire back on fully, but I'm doing a compression test just for my own edification.

Hope for the best!

 

[section525]

I just sent you a six page PM and you didn't have the wire on!?

 

[boominXplorer]

detonation?


LOL section: see my avitar tital

 

[V8BoatBuilder]

I just sent you a six page PM and you didn't have the wire on!?

Bingo.... I am hereby firing myself from working on my truck... It was a sparkplug wire issue, I got ****y and didn't label the wires when I ran them, and also didn't bring a printout of the coil pack connections into the garage with me. I swapped 5 and 6 at coil. DOH!

Thanks guys - she runs awesome. Misfiring sounds mighty different through modified merge collectors