Hi gang:

I've put this out there a couple of times, but haven't got a clear answer yet.

So - How many oxygen sensors are there on a 1999 4.3 blazer?

I saw a thread on a 2001 for there being THREE. Is that true for the 99' , as well? If so, are they all the same part number?

Thanks all, once again!

 

1998 and newer have 3, and they're all the same.

 

Hey, thanks Captain.
Any special tips on replacing them?

 

Unless you're getting a DTC concerning the B1S3 sensor, (downstream of the converter) leave it alone. Its sole purpose is to monitor the catalytic converter, it does NOT affect engine performance.

 

So, you are saying I could get by with just replacing the two upstream sensors in an effort to improve MPG, right? Just leave the rear (downstream) sensor alone, unless that code shows.

I continue to get a P0404 code even though I have a relatively new EGR valve, which was cleaned recently when I replace the gasket with one having a screen. I seem to be barely getting 14.5 MPG with some sense of hesitation or surging. We should be getting out of the winter gas blends up here in Minnesota soon, so I thought I would just put all new sensors in and go from there. I thought replacing all 3 sensors at one time would be a good approach, so I could put that issue behind me.

I always appreciate your comments in my efforts to understand this creature GM created.

 

Only the upstream sensors affect engine performance... Save your money.

The EGR valve, MAP, MAF, TPS, ECT, IAC, IAT, CKP, CMP, ignition module & ignition coil affect all cylinders equally, so don't waste time, money or energy on them looking for a cylinder misfire.

 

Ah So, very fine. Thanks for the great info,Captain.
I'll apply the remedies shortly. Gonna order the parts now.

 

AC Delco sensors are good, and so are Denso. AC Delco will easily go 100K miles. Denso is cheaper, and has a faster response time, but they don't last quite as long.

 

it will cause problems if it shows to lean