I'm chasing down some highly erratic timing issues. I want to rule out a couple areas by replacing the 19 year old factory parts. Is there a 'known' much better than GM stock issued:
~ Knock Sensor
~ Oxygen Sensor
~ Oil Pressure Sender??????

And does anyone know the average cost of each of these? (I want to be sure I've budgeted in these parts without any big cost surprises)

I appreciate it, Nitro

 

O2 sensor and oil pressure sender won't affect timing. Knock sensor can.

Any parts store O2 will probably work. I don't shop at Pep Boys or any of the chain stores- they sometimes sell low quality parts so they can charge $2 less than the guy down the street. I buy where real mechanics buy their parts. The quality is typically better. Real mechanics hate "come backs" due to defective parts because they lose all profit on the job by having to do the labor twice.

Oil pressure sender is a given for any 3rd gen. They almost always need replacing. I've had good results with Standard brand senders but just about anything works better than the 20 year old stock piece.

As for the knock sensor you can temporarily bypass it to see if it's the cause of your "timing issue". Just buy a $.25 resistor at Radio Shack (3900 Ohm) and put it in between the KS wire and a good ground. The ECM will think the knock sensor is there but, obviously, it will never hear any knock even if there actually is knock. I wouldn't drive around like that forever but for a quick diagnostic test it's 25 cents well spent.

 

Thank you for sharing the KS bypass info, I'll do that this weekend. As for the O2 sensor, it's (was) my understanding that a sluggish sensor could affect the timing.
I sure agree with you on the Pep Boys/Kragen/Grand Auto/Autozone type parts. I first learned definitely NOT to purchase any electrical rebuilt parts and now I just go for the oil and cleaning supplies. Thanks for getting back to me on this subject; it's greatly appreciated. Nitro

 

The ECM pays little attention to the O2 sensor until it reaches operating temp (about 600*F). The ECM knows when it's up to temp because the voltage starts jumping up and down very quickly. In fact the ECM measures something called "cross-counts" which is how many times the O2 jumps above and below ~450mV. So, yes, a sluggish O2 can affect the ECM, at least to the point that it might never trust it as being "ready" and putting the engine into closed loop. I don't beleive it affects the ignition timing very much, if at all. If there is any effect at all it is probably very modest.

Think about it this way.... when the O2 is cold and the ECM is definitely ignoring it the ECM is still making timing changes based on engine need. It's not like the computer tanks the ignition advance until the O2 sensor is ready for action.