2.8 to 3.1

[jeep2.8]

Thanks Betterthanyou,

So far converting to TBI seems reasonable. The biggest hurdle ahead is likely all the wiring. I will probably try to hook as little to the computer as possible and need to get a code reader also.

Thanks

[geoffinbc]

It is pretty simple. Fuel lines and wiring will be the only hard part. But if you can scrounge up a donor it is all just a bolt in. Nothing significant in the layout or structure changed on the S-truck from 82 until 93.

[jeep2.8]

Hi,
Can you help me out, where is the O2 sensor located? I found S15 in the wreckyard and plan to take the TBI components from it? I thought it is on the collector, but on that engine there is an air pump inlet there.

Thanks

[geoffinbc]

It will be after the 2 exhaust manifolds join in the Y pipe of the exhaust before the cat converter.

[jeep2.8]

This may be a bad news... On my truck air injection does not operate. Now, if O2 level is significantly affected by the fresh air injection then computer may mess up the fuel mixture. On the other hand injected O2 is meant to burn out hydrocarbons in the exhaust and this process may be complete by the time air reaches O2 sensor.
I planned to install O2 sensor at the location where air is injected - at the end of exhaust manifold. What do you think, may it still be ok?

[geoffinbc]

O2 sensor never gets affected by AIR. AIR only operates in open loop to help reduce emissions while the ECM has no O2 reading and is using fuel and timing maps to control the mixture. Remove the AIR if you want as long as you don't get a visual inspection no one will know it is gone and you will pass emissions as long as the truck is warmed up.

DO NOT install the O2 sensor where the AIR pump injects air. Plug the AIR port/ports and put the O2 sensor in the Y pipe so it gets an average reading from all 6 cylinders and bases the fuel trim on that. This makes the engine more happy.

[jeep2.8]

Thanks,
It was a good answer.
However, on the donor s15 I noticed that O2 sensor was on the right side exhaust, at approximately the level of oil filter. Was this the original location, I don't know.
Theoretically the O2 concentration should be the same for 3 cyl. as it is for 6, if the engine is ok. The only difference is in the temperature range - sensor will warm up faster and will be in a hotter environment.
Do you happen to know what is the temp. range the O2 sensor is meant to operate? I still like the idea of plugging the sensor to air inlet.

[geoffinbc]

Yes the vehicles used to only read off one bank of cylinders. As the years passed this was changed to the Y pipe and some vehicles, like the Camaro even used 2 sensors (one in each bank) although it was still OBD I.

My AIR fitting is RIGHT at the #3 exhaust port on the manifold this is so close to one single port you would basically be reading off one cylinder. Although the trucks did use a variety of manifolds over the years yours may be different.

I am really going to stress using the Y pipe for the O2 sensor location. The 60* V6 is prone to un even fuel distribution because its narrow design makes for short runners in the intake which are all of different lengths. This is why it is important to get the best average reading you can. If you are worried about the sensor being hot enough then install a heated sensor. It is very simple to hook up. I have a how to on my website. With mine installed my truck will never fall out of closed loop once warmed up.