Hi, I've just replaced the missing thermostat in my 350TPI '90 Camaro. The temp gage reads a normal 200-230 now. However A cruise around the block gave me hesitation problems when accelerating and it died once. After checking the flash codes, I found a code 44. Which suggests a faulty O2 sensor reporting lean. Is there a procedure to test the O2 sensor? Any help greatly appreciated. Rockstar

clear the computer by disconnecting the negative cable from the battery and then start, take for a drive and recheck the flash codes if still coding on 44 check connection at the 02 sensor and repeat above or remove sensor and clean and recheck. that's what I do before replacement worth a try
Chuck

Thanks chuck!

It was the o2 sensor, I attached a multimeter, the readings were very erratic, would shift rapidly from .55 to .25 then back and up when the temp gauge read 200+deg.

After reading a little about 02 sensors I discovered that they are not used by the ecu unless the system is in closed loop.

I guess when i repaired the thermostat, it enabled closed loop operation and the o2 sensor to come up to operating temp, so I would have seen it when the thermostat was missing.

I am about to take it for emissions testing, its been sitting in a garage for 8 years.

Have replaced oil with synthetic, 02 sensor and water temp sensor. Replaced the gasoline with Premium unleaded with 10% ethanol. The car comes up to temp well, and theres' a little blue plume when the car starts from the valve stem seals, which I plan on doing later some time.

Do you have any recommendations on getting through emissions testing?

Thanks Rockstar