I have a '91 F150 with 99,300 miles on the clock. The truck started pinging under moderate-to-hard acceleration about 3000 miles ago, so I decided I'd do a tune up. Bought and installed new plugs and wires today, but the pinging is worse than ever (I guess it's pinging... just a light tapping--sounds like tapping on tin foil).)

Anyhow... This isn't good... I have no idea why it would be doing this. I put a new fuel filter on just about 25,000 miles ago... have run regular unleaded forever with no problems.

Thoughts? What to check next? I'm getting the truck ready to sell and want to get this fixed before putting it up for sale.

Thanks,
Mike

 

what engine?

 

It's a 302. Also... replaced EGR about 32,000 miles ago (December '99).

-Mike

 

are you sure its pinging? it could be coming from the valvetrain (bent pushrod, loose rocker, etc.). if its pinging, have you played with teh timing at all? if so, go back to stock and see. also, have you tried higher octane gas? try running some 93 octane, if it goes away tehn you know its pinging. good luck!

 

Running on 93 right now... still pinging. My thought is that the timing chain (sprocket, actually) may be worn out. 99,300 on the truck. Hard miles, mostly.

What do you think?

The truck was doing it all the way home today under minimal acceleration and even under minimal throttle required to maintain speed. Can't find any problem with tune up stuff... plugs are tight, new distro cap and rotor okay, wires on... Don't know why it would behave worse after a tune up than before... Plugs gapped per factory specs.

-Mike