Re: 90-92 areostar
How did you come to the conclusion that it's not knock...aka pre-ignition? Is the noise only under acceleration? If so, I would almost guarantee it's pinging. Try either running a higher octane gas or retarding the ignition timing a bit to see if the problem goes away. If the problem does go away, disconnect the SPOUT connector and reset the base timing to the spec listed on the sticker under the hood with a timing light. Reconnect the spout and take it for another test drive. If the noise is gone, the timing was probably too far advanced. Check/replace the knock sensor as well.
If timing wasn't the problem, it may be time to pull the heads and scrape all the carbon off the top of the pistons and in the combustion chambers. While it's off, might as well do a valve job. The carbon buildup can retain enough heat from the last power stroke to ignite the fuel/air mixture before the proper time....thus creating the audible knock you hear.
Hope this helps.
1992 Ford Bronco
E4OD- B&M Stage 2 shift kit
Full 3" stainless Bassani Exhaust
32" BFG's/stock suspension
"No replacement for displacement."
"Our lugnuts require more torque than most Honda's produce!"