Are o2 sensors needed?

[Drift99]

Im just wondering if o2 sensors are needed for the 1uz to run properly. I currently have open headers and no o2 sensors hooked up. The engine doesnt seem to want to hold an idle on a cold start. I need to hold the gas at 1000rpm for a minute or so to let it warm up a bit. Then it idles great around 700.

What exactly will a 1uz run like without the o2s hooked up?

Thanks,
Jake

 

[poorsupra]

if you dont have the primary and secondary o2s at least plugged in you will get a "clogged cat" code and your car willl run in limp mode. usually spits and sputters.

 

[George_R]

depends on the donor. Some very early UCF11's run just nice without them. But all 1UZ's will start and idle without all 4. Non-vvti crowns and celsiors may lose idle when cold for the first minutes after battery disconnecting (call it a feature), but unless you disconnect it again it would then idle ok at any coolant temp.

 

[Drift99]

Thanks guys. Its from a 91 LS400. The engine ran flawlessly before pulling it out. After pulling it out, I blocked off the EGR exhaust port since I will be removing all emissions components in the future. The EGR stuff is still on the engine. Could this be causing my cold idle issues?

When trying to start the engine cold, the engine will idle at like 400 for a split second and cut out and die as if the computer is cutting the spark.

After letting the engine warm up a bit (holding peddle at 1200rpm for a minute or two) it idles solid at 550rpm. The day before it would idle at 700 once warm so maybe temperature is playing a roll?

I tried unplugging the IAC plug when it was warm and idling at 550rpm. There was no difference in rpm. I put my thumb over the tube and felt vacuum. The vacuum was the same strength with and without the IAC plugged in. The IAC should be good since it was fine before pulling the engine out but it could possibly be bad.

Tomorrow morning I will be getting an exhaust installed so The o2 sensors will be hooked up. Hopefully that will solve my problem.