I have a 1991 305 tbi, bottom end is a flat top short block out of a 1985 z28. So i have flat tappet after market cam with hydraulic lifters. Ported, not polished, heads and intake, did all the tbi mods other than grinding the butterfly rail and havnt bored the throttle bores yet. 1.6 full roller rockers. Everything but the rotating assembly has been rebuilt from the intake to the transmission. I am going toput a roller block back in it so i replaced the oil pump and just didnt worry about bearings or anything. Hooker long tube headers, custom y pipe and hooker cat back. Do not have cats on car. Have underdrive pulleys on the engine. I cant really think of anything else right now. I just recently bought another 1991 rs to use for parts and noticed that pretty much all of my vaccum hoses were hooked up wrong. After i fixed them all i started getting trouble code 13 o2 sensor circuit. So i bought a 4 wire o2 sensor for it.just wired tuat up and installed it yesterday. Didnt seem like it made much of a difference but the check engine light stayed off so i was happy. Exhaust still smells pretty strong but whatever, i still have a lot of things to do to the car so i can deal with stinky exhaust until i figure out the issue. So my question is this... When the exhaust shop put my custom y pipe on they suggested that i install my o2 sensor after the y in the intermeinter

 

Sorry, my phone freaked out on me...

So anyway, the o2 sensor is on the intermediate pipe after the y, so it is reading fuel from both sides of the engine. The exhaust guy said this would give me more accurate readings, it has been a year and my car has been running pretty rich all along. I am wondering if moving the o2 sensor to this position will actually give the computer false readings since the stock location only reads exhaust from one side of the motor. Which is true? Should the o2 sensor get moved back forward of the y into the header or is it fine to have it reading both sides of the exhaust?

Thanks.

 

It may be too far back (too cold) to get accurate readings there, a heated O2 would be a good upgrade. As far as the additional flow, no that will not change the reading. Exhaust leaks will change the reading (obviously)

 

Thats what i was saying. I just installed a 4 wire heated o2 sensor yesterday. The light was off and it was running fine. Throttle response was a little different, not sure if i wuld say it is btr gta drive a few more days i can determine that. But anyway at cruising speeds and city driving the ses light never came on. But wen i was on my way down the highway i gave it a little gas, not like wot or anything but i was passing someone on a pretty steep hill, and after i got of the throttle and came back down to cruising speed the ses light came on. I pulled into bojangles and pulled the code from the ecm and i got code 13.read a couple threads that said its a bad o2 sensor, bad or malfunctioning tps, or faulty o2 wiring. Well the o2 sensor is brand new and obviously working or else my car wuld be running like dirt, i checked all my wiring and its ll good. The tps is like 6 months old. Anybody have this issue before. Also forgot to say i have a 160 degree thermostata and a hypertech stage 2 chip.

 

So I figured it out. The guy that did my exhaust extended a green wire with a white stripe to my o2 sensor and the purple wire that was supposed to go to the o2 sensor was just dangling out of the wire harness on the driver side where it was supposed to be, lol. So I hooked the o2 sensor to the correct wire earlier tonight and we will see tomorrow how it runs. But now I have a green wire with a white stripe unplugged and I have no clue what it is supposed to go to. It runs through the same harness as the blue wire that is going to the knock sensor on the passenger side of my block, runs up that harness behind the air conditioner compressor and through the harness across the top of the engine and past the egr valve. That is as far as I traced it today.I have another 1991 rs for a parts car but the green/white wire is spliced and it is running to the knock sensor. I didn't have time to find the blue wire on the parts car and trace it but on my car the knock sensor connector is not spliced and the blue wire runs all the way past the egr through the same harness as the green/white wire. Anybody have any idea where the green/white wire is supposed to go?