I've been trying to solve my rough idling 360 (spark knock pre-ignition) for weeks. Even my mechanic couldn't help. Thank you soooooo much for mentioning the intake snorkle! What you wrote below makes total sense, but, I hadn't thought of it!
"The reason EGR helps with ping is that it cools the intake charge temp. So anything you can do to cool this charge the better. I actually don't run EGR on my Jeep, but it doesn't ping either.
One more thing that will help, is the fresh air intake snorkel. I tried running an open element and it made the pre detonation only worse. Remember, cooler is better.
Hope this information helps, and make sure that you reply back and let us all know."
I've had my GW for 14 weeks and been trying to solve the rough idle (only when engine is warm. It idled smooth when cold until it was fully warm). It is there in Park & Neutral and worse w/ the tranny in gear. The PO had a ripped up fresh air intake snorkle (ripped near the air cleaner) and I never thought......
My JEEP mechanic said "some of them just run rough". So I've been trouble shooting it on my own ever since. Timing adjusted, EGR-tested good, PVC valve replaced, PVC filter cleaned, spark plugs replaced, new cap and rotor, AMSOIL air filter, etc. The cap & rotor helped a little as did the less restricting AMSOIL air filter, but, 3 days ago I replaced the air intake snorkle (Mighty Flow #96077 2-5/16" X 3-11/16 RECT X28" LG W/90 degree twist. $10 @ PepBoys) and now it idles much, much better. I'd say I have 1/10th the pre-ignition I had -if not less.
Yes, cooler is better!
'91 GW 360/727/229/3.31s "The Swank Tank"