O2 sensor part #

[birdflewby]

I have an 02 trans am that has a procharger with hopefully all the necessary upgrades. I recently had it tuned and they changed the pulley size . Before i had it tuned i had a "running rich on both rails code". After tune, the ses light is off but lately i get a lot of hesitation when accellerating, then it "clears its throat" and runs like hell. I have checked and cleaned the maf, ait sensor, and tested voltage for the o2 heaters. All seem to be ok but i did notice that one upstream o2 is a replacement, beleive a Bosch, and the other side is factory. Car came with headers and rear o2's deleted. Would different o2's cause such a problem. Would like to switch to Denso's but Autozone has multiple part #'s. Anyone know which ones to get? 234-4000, 234-4025, 234-4087 Thanks for any help.

[2002ssslp]

I do not know if the O2 is the problem, I do not have much experience with the newer blowers but I did have some experience with the old roots style huffers from GM. 471, 671,871. I feel with fuel injection you may not be getting enough spark advance on the low end. What does you tune map say ?

[pajeff02]

I always recommend Bosch P/N 13111 oxygen sensors. They have a nice long harness and work great with headers -- no extensions required. I would get a scanner on the car and check out the live sensor data before you start throwing parts at it. Any chance you have a vacuum leak or outside air infiltrating the exhaust above the sensors?

[birdflewby]

The Actron scanner that I have only captures a live snapshot, not a constant live view. What's an easy way to go about checking for the vacuum leak?

[pajeff02]

Inspect the air intake ducting, the throttle body, and especially the PCV system for leaks. There is also a vacuum source line on the back of the intake that runs to the HVAC system and over to the passenger side of the engine bay that can be the source of a leak. The stumble I had on off idle throttle was a hacked up MAF housing discovered after I purchased our car. Is it the stock MAF or an aftermarket unit?

[0rion]

who tuned the car? It could easily be a mechanical issue but the tune would be suspect unless it was done by someone that knows what they're doing. Still running the MAF or is it speed density and how much boost are you running?