Ok. I'm not sure if this is weird or normal.

Everywhere i read, when you first start your car in cold weather, or maybe just after a cold-start, the engine is sluggish and doesn't really respond well.

My car feels like it's juiced up when i cold start, even in very cold weather. The shifts are much harder than when it is warmed up and the engine screams if you mash it down. If anything else is imagined, the responsiveness of the throttle after a cold-start is not imagined, it's noticeably better.

Is this a symptom of maybe a lazy O2 sensor, so that once it goes into closed-loop, i get readings that are slightly wrong?

I also noticed that once in closed loop, any sort of uphill part-throttle (basically any part-throttle under stress at low speed and rpm) causes the engine to sound like it's missing/pinging like crazy, the entire car starts to resonate and shake. The way i stop it is push the peddle down further and it shifts to a lower gear and the rpms go up and the problem goes away as long as the rpms are high (>2000).

When it's cold shortly after starting the car, this doesn't happen.

Now, i know pinging can be caused by bad gas, and i do use regular grade. The timing isn't advanced more than 2 degrees, and this happens no matter what brand of gas i use. Putting premium in it reduces it somewhat, but it still occurs a little.

 

Well genrally speaking when people describe there cars as being sluggish and what not when they first start the car its usually a carbed car not really the case with fuel injection. Next motors love cold air so they do typically run better when there first started. This is because once hot ive measured underhood temps to run upto 150 degrees! So the hot air and head soak just kills a noticable amount of hp. No you mentioned the pinging that is usally the result of ignition timing being too far advanced. I would try retarding it back to stock as it should be advanced electronically and by advancing the timing the car thinks its somewhere its not possably over advancing the timing. Now you also said that this dosnt happen when the cars cold. This is probably because once thoes cast iron heads heat up it greatly eases combustion (and detonation) because they retain so much heat.

 

You have to retard the timing well below stock for pinging to be eliminated. Plus, the problem goes away when i mash on the gas more, which only increases the timing.

Two issues are suspect in my eyes. I'm not running on all 8 cylinders. Or a sensor is mucked up.

This only _only_ happens when the car is at very low rpm under load ...meaning in 4th gear under some type of engine load, like going up a hill at 30mph. As soon as it downshifts, no more problem.

The noise sounds like it's exhaust related, rather than intake, which would be a signof pre-detonation. The more i think about it, the more i'm suspecting a cylinder is down ...or my O2 sensor is lying about oxygen levels and the ECM is compensating based on bad values once in closed loop and at that rpm band i am dumping too much fuel in.

Either that or maybe i have weak piston seals and under load I lose compression and that's the sound i'm hearing.

 

Well that is typically where pinging will occure under a heavly load like climbing up a hill in a numearically low gear like 4th. Steping on the gas does advance the timing but it also enriches the fuel mixture and downshifts. Its entirely plauseable that a sensor is messed up and your computer is comensating based on bad data but in order for pinging (detonation) to occure somethings got to ignite the A/F mixture too soon in many cases, timing. So you may have a bad ignition modual or something but i would check with a timing light to see how your ignition systems electronic advance is working.