1993 B2600 Acceration rattle
 

At 140,000, my '93 b2600 has developed a tin-like rattle when I accelerate. This only happens when I push the gas pedal down in any gears and while the vehicle is in motion. This does not happen when pushing the gas pedal in neutral. It doesn't happen when I am coasting, even if I am in gear. Since it only happens while the vehicle is in motion, I am unable to pinpoint where the sound is coming from, however, it does sound like it is coming in from underneath the console.

My father said it might be the heat shields, but I am having trouble finding them in the repair manual.

I replaced the drive line about 2000 miles ago, as the needle bearings had rusted out.

Master and slave cylinder and the valve cover gasket has also been replaced.

All suggestions welcome. Thanks!

Kyle

Sounds like the engine might be "Pinking" or "knocking".
Check the engine timing & increase you petrol octane to a higher grade.

.....and when was it the last time a tune up was performed? (new plugs and wires)

It was tuned up last at about 110,000, when I bought it. I will look into that though. The simplest explanations are often the correct ones, eh?

Yes, keelboatkyle.
Also look for vacuum leaks and consider replacing the PCV valve and rubber grommets.
I am not totally familiar with your engine. But at that mileage I would also check the ignition coil/distributor rotor and cap--- or coil pack if that is what you have.

Check the Catalytic converter heat shield or the heat shield attached to the body/frame underside directly above where the exhaust routing is. there is also a heat shield on the stock exhaust manifold. get under there with a rubber mallet and start tapping things until you find it, mine was the cat heat shield, I have even had the actual catalytic converter rattle because the guts of the cat broke loose inside the housing.

After checking heat shields, problem still persists...
 

I just checked the heatshields around the exhaust system and they are corroded. They are loose and rattle a little bit when tapped with a mallet or moved. I tried taping them with foil tape to secure them, and took it for a test drive. It didn't fix it. See photos here. I removed the foil tape after. The catalytic converter seems fine and intact.

I also shot a of a potentially related problem of mis-firing or back-firing when the rpm decreases rapidly. It is slightly audible after the revving goes down.

I shot another while driving on the street where you can hear the "rattling." Around 21 sec you can hear it pretty well.

My father weighed in again and thought maybe something to do with the emissions.

I will next check the coil and distributor rotor and cap.

I will also check the engine timing.

Could changing spark plugs and wire improve a backfiring or misfiring?


Thanks for everyone's thoughts.

GO HAWKS!

Definitely, misfiring should improve, actually should improve when you replace ignition wear parts.
If you do have a vacuum leak and you fix it it will also improve.

it sounds to me like like one cylinder is not firing (at around :21 seconds of the video). do you feel the car loses power? if that is the case i would start by doing what tanprotege suggests.