First of I've been adhered to this forum since 2004 (lost old account) and you guys have taught and saved me a lot and I thank you all.

Now, I have a 2000 MCSS with a p0300 I've been hunting for months. Only has about 110-115k miles. I have zzp downpipe, k&n, and stick everything else. Mobil 1 oil and valvoline dex 6 fully sythn trans fluid. I have new fuel filter, new cat, new plugs (ax delco 41-101), new Delphi wires, new coils all 3, and new ICM. I'm assuming fuel pump is ok because it never cuts off or acts like it wants to. Starts are a few extra seconds and temp needle goes 1-2 notches past halfway at idle. Coolant is fresh and green, thermostat is new, 180. Swapped injectors with working spares and still p0300. 2 days ago It started flashing cel at about 35 mph and is in limp mode. I'm pretty much all out of suggestions pls help.


Oh, I have to add coolant every few weeks and I haven't had any gasket jobs done. No white smoke, no funny smells, no coolant puddles. Just rough idle and attempt to overheat at idle 1-2 notches then fans kick on then temp goes back down.

 

Think I got it guys. 2 bolts are missing from the intake manifold. I guess they vibrated out or just a weird unexplainable act. Also explained my small oil leak. I'll go to pull a parts and grab the same two bolts. Should I use thread locker or anything or just torque to specs without anything?

 

I usually use white GM sealant for intake gasket bolts. Glad you got the issue figured out.

 

Good deal. I'll try to grab a tube. Couldn't go pick up some bolts today, been busy and they close at 5:30. I'll check out my pcv valve also since there's an opening in manifold. Thanks for the info sir!