On my 95 Lt1 , I have a small stumble at low rpm or when going real slow in top gear , just off 1200 Rpm or so, Noticed a slight exhaust leak and took it to the exhaust shop and on the lift I saw there were NO O2 sensors at all!!! *no cats either but the car came with a cat delete- imported to South Africa*.
General performance is very good at WOT or when hustling. The "lean" stumble is not too bad , but a little irritating. I see no wiring going to where the o2 sensors should be , don't know whether the wiring exists.
I have ordered a cable , tunercats and a data logger from the US to really see whats going on , local vette shop is really not that savvy , a small hand held scanner and its throwing no codes at all. He cleaned the TB and never actually NOTICED no O2 sensors.
Not sure what I should do - put bungs in and reinstall sensors and try wire em up and flash the ECU with a stock map or just richen up at low throttle positions and leave em off?
When the car is cold , it has WAY better throttle response untill it starts warming up when off idle response isnt quite as crisp.
Feels likes its running lean to me when it gets warmed up. When giving it welly , as I said before , it performs. But driving in traffic is a bit of a PITA.
I do have a FSM , but can't really find anything on what to do if the o2 sensors are missing. My brilliant v8 pal says its most likely that the wiring has been fitted with a fixed resistor or has been programmed at a fixed resistance to fool the ECU that O2 sensors exist.
Any suggestions?

 

Very likely what you are looking at are the rear O2 sensor ports which would have been located after the cats. If the cats are gone and the computer adjusted properly these can either be removed or replaced with a simulator.

If the car isn't setting any codes I can promise you that the front sensors are intact. They are just way further up and much harder to see.

 

I and the exhaust guy checked m we can see NO O2 sensors anywhere on the manifolds up to the engine and nothing after the manifold glands... ?? Where would the primary o2 sensors be? surely they cant be so well hidden you cant see em from the bottom or the top ? Initially I thought it might be a vac leak , but can't find anything.

 

I've had headers on my car for so long I can't remember exactly. Maybe somebody with a stock 95 can post a picture.

You can't program the front O2's out of the computer, it will look for them and it will set a code.

If they really and truly aren't there I can only think of 2 possibilities.

1. The car is in fact setting a code but the service engine light is long since burned out. It's a typical redneck trick to just remove the bulb. Make sure it's not setting a code by checking the ECM.

2. Maybe whoever programmed the computer in order to remove the rear O2 sensors set the closed loop enable temperature so high that the car never tries to go closed loop. If it never tries to go closed loop it will never see that the O2's aren't there and will theoretically never set a code. It will also not run that great and not get good gas mileage either.

If you can get your hands on a scan tool like a GM Tech 2, it will tell you if it is in open or closed loop, it will show you the actual O2 sensor voltage output, and it will show you any codes. If you can't get access to anything like that, a laptop computer and the proper data cable and software will do the same job.