'93XLT with ping, knock, whatever

[dgrisman]

I've a '93 XLT (97k) with an engine that makes a lot of noise under the following conditions:
Fuel 89 octane or less,Makes less noise with premium gas
Makes noise when engine is warm; makes no/less noise when cold.
Makes noise during acceleration or during increase engine load (going up a hill), less of a problem at constant speed.

The noise sounds like loose nut and bolts rattling in a metal pan. The service manager at the local dealership called it "spark rattle". Couldn't find any info on that terminology.

Before I take this vehicle in for service again, can anyone give me an idea of what might be the problem? And what would need to be done to fix it? Many thanks.

 

[Bruce L]

I had the same problem ('92 XLT w/ 108000 miles). It's pretty common. My successful fix: I took the plenum off and tightened the studs/bolts for the fuel rail to the lower intake manifold (they were very loose). I replaced the gasket between the fuel rail and plenum. Ever since then, no knock and runs great. I'm just waiting for the warmer weather to see if it last through the summer! Hope this helps.