I have a 2001 Grand Prix SE with 43,000 miles on it, it has the 3100 engine with the 4t65E transmission. It was my grandparents second car and it was hardly ever driven. It was garage kept and is in great shape.
I would like to preface that my previous vehicle was a 1994 Grand Am with the 3100 and the 4t60 transmission, so I already know all the quirks of this drivetrain. This means I have done the intakes, head gaskets, water pump, hoses, thermostat, removed dex-cool, etc. Basically the entire cooling system has been revamped because it sat with dex-cool in it for 15 years. I've also done all fluids, filters, plugs, plug wires, oxygen sensor. Essentially any engine or transmission related stuff that you would replace after 15 years of sitting I have done.
I have a few questions about this vehicle.
1) My first question seems to happen in the summer. The temperature gauge will come up to the first large mark (195f according to my scan tool) and sit there while I am driving. If I sit and idle for awhile the gauge will creep up to the 210f mark (actually 225f according to the scan tool) and then quickly sink back down. The cycle will continue for as long as it sits. I know this is when the fans kick on. However before I did all of this work, I don't remember the gauge ever creeping up like that. (Now granted I only had the car for a month or so before I tore into it, so for all I know it did do this and I just didn't notice.) I also didn't see this happen with my Grand Am either. Is this normal for this vehicle?
2) My second question is similar, but is happening now that it is winter. The gauge will come up to the 195 mark, but while I am driving/idling in city circumstances the gauge will drop a few small tick marks down from 195, then swing back up a few tick marks above 195. This cycle also continues back and forth. The heat in the car seems to feel the same. If I get on the highway it stays constant 195f. My first thought was "hmm some air in the system..." So I popped the bleeders on both sides and no air came out. I am stumped. Again I don't remember this on my previous Grand Am, but this is the first winter with this car and it is super cold right now. Is this normal?
3) I know people on here say these N/A engines tend to knock pretty heavily. I am seeing up to 10 degrees of KR at WOT. This isn't going to damage my engine right?
4) I have a random misfire at idle. I have tried everything suggested. Cannot pin it down. I swapped ICM and coils, still present. When I pulled the fuel rail I tested each injector, they all OHM out properly and their spray patterns were perfect. Cleaned and checked for holes EGR. I used propane to try and find a vac leak. Nothing. Any thoughts?