1985 Pontiac 6000,2.5 litre?

Question

I've been running 93 octane gas for years ,recently I changed the distributor .Now the car knocks somewhat,and we tried adjusting the timing ,but it still knocks .Is there any chance lowering the octane would help with the knocking (as someone suggested to me)and should I try 87 or 89.?

Answer 1

REDUCING the octane rating will INCREASE the knock in the engine.
When you replaced the distributor, and adjusted the ignition timing, did you follow the instructions?
There is a specific procedure for adjusting the ignition timing. The ALDL terminals "A" & "B" must be jumped with a paperclip, or the timing will never be correct.
The computer expects to see the timing "based" at a particular position (8° BTDC)?, and after the car starts, the PCM will advance the timing based on temperature, run time, etc.
The PCM also uses the ignition timing to stablize the idle, along with the idle air control.
Refer to the repair manual for the correct procedure if it isn't still on the VECI label under the hood.
The manual is available from a parts store or book store for < $20.00, or you can go to the library and use what they have in the REFERENCE section at no cost.

Good Luck

Answer 2

i would try 87 octane and recheck and set the timing, you have nothing to lose........may want to clean and re-gap the plugs or buy new ones