Our 04 GP recently started knocking so we switched to premium fuel. That solved the problem for a while but now it's missing, hesitating, so on like a madman. No engine codes, just terrible mileage and running.

It's been a great car but now has 150k+ on it and this has started.

Going to do the standard tuneup but wondering if anyone else has seen this happen and what you did to correct.

Does it have original plugs & wires? If so WOW! Get ACDelco wires from Rockauto.com and any quality (autolite, ACDelco, NGK) double platinum or iridium plugs. PVC & fuel filter would be a good idea too. As far as fuel, find a station that sells "Top Tier" fuel and use that if you can. I'm very surprised you can hear the knocking.