OK, so I'm all set to get a new O2 sensor for the Blazer, but I discovered that there are two different part numbers for my year because it depends on whether it is 3 or 4 wires...How do I know which kind of sensor I have, since I can't get it off to check? And can anyone tell me of a major parts chain that carries the AC Delco brand? AutoZone (which is closest to me) substitutes the Bosch, which I have been advised NOT to use. Do I need to purchase it from a Chevy dealer?

 

My advice would be to crawl underneith and see if there are 3-wires (w/o interm design - PN 25312179 or AFS74) or 4-wire (w/ interm design change - PN 25312184 or AFS75). I think you'll find that you have a 3-wire as that is all that GMPartsDirect.com shows for your application, although it does show another PN, but I cannot find anything more about that PN... The AFS75 is what the rest of us have for our sensors and that is a 4-wire sensor.

As far as were to get them from. Well, if you can't find them locally at an AC Delco store, you could grab them from RockAuto.com. They seem to be the best online source for AC Delco sensors as far as a retailer goes. You could go with an eBay seller as well. There are a few sellers on eBay that sell genuine AC Delco sensors, but I could not find any AFS74 AC Delco sensors on eBay...

Good luck! Even if you do go to the dealership, it shouldn't be more than $65, but you can definitely do better. Give 'em a call and see (after looking underneith).

 

I will do that....Found a place called oehq that only deals w/Motorcraft and AC Delco online. They are only asking $45 for the sensor, and free shipping! Might be worth waiting the few extra days to have it sent, and I'll check out the site you suggested to compare pricing.

OK, I just checked and they are the same price, and free shipping...I take it that they are good to deal with? I've never ordered parts online so want to go with the trustworthy ones!

 

OEHQ.com looks like a pretty decent site. I have not purchased from RockAuto.com before, but know MANY people that recommend it highly. And I basically only use GMPartsDirect.com for their catalog to verify part numbers I find in my other references and to see what the prices for the parts are so I can gauge how much the dealerships are inflating the prices.

 

OK, just wanted to let you know that the new O2 sensor solved 95% of my problems...Blazer has lots more pep, and the idle is much improved (although still not perfect...still gotta figure that one out). My mechanic was surprised that I had a 3 wire, his wife's 94 Bravada only has a single wire with the same engine...that's why at first he didn't think that it would make that much of a difference in the performance. I hope this helps my gas mileage improve!! Thanks for all of your help with finding the correct part.