gbettner

iTrader: (2)

Hello everyone, I have a pretty urgent issue I have to figure out.

I keep getting lean datalogs. I have a 90-92 speed density setup 7730 ecm, I converted my 89 TBI harness to a TPI speed density harness, I also upgraded to a heated 4 wire O2 setup.
After discussion with tuner and 4 datalogs we've concluded may have an issue with info from the O2, I've either wired the updated 4 wire O2 wrong or have the wrong one. I got an "AF75" I think from the junkyard as reccomended by a forum member.
I got online to order a brand new O2 for a 90 camaro and only one wire versions pop up.
My question is....
Is there a 4 wire version of the o2 I need ( need exact part number) or do I need to just go back to a standard 1 wire version?
Please let me know if you are knowledgable in this situation. I'd like to get ordered.

Thanks in advance!

RBob

iTrader: (1)

The part number you are looking for is AC Delco AFS-75, that is the 4-wire heated O2.

The stock TPI cars ran a 1-wire as it is located in the exhaust manifold. Not far from the exhaust ports.

As far as running the 1-wire or the 4-wire (heated), depends upon it's location.

RBob.

84Elky

RBob --

A lot of 3 .vs. 4 wire debate over time. If I recall correctly, you used to recommend the AFS-74 3-wire because it was tuned to the GM ECM PID fueling algorithm. Just curious what if anything may have changed your mind to use the AFS-75 4-wire. If better, would appreciate your insight as to why.

RBob

iTrader: (1)

The advantage of the 4-wire O2 over the 3-wire sensor is in the sensor ground. The 3-wire sensor still gets the ground via the exhaust system. So there is a path from the sensor body to the pipe, pipe to headers or exhaust manifold, then on to the engine block.

While the 4-wire sensor has a ground wire that can be run straight to the ECM.

As for this thread I only answered the OP question as to the part number of the sensor he has to replace.

RBob.

gbettner

iTrader: (2)

Well thanks for the responses but I'm just now seeing them. Must have missed the notifications.
Anyways, I found a kit on ebay to convert a standard one wire O2 to a heated 3 wire O2. Came with harness, adapter, and instructions.
I ripped out all my wiring for the afs-75 O2 4 wire and started from scratch.
I'll be damned if it works great now, good readings that made my tuner happy. turns out I wasn't lean I was rich. I'm sure I had something hooked up wrong on my 4 wire O2.

Gary Anderson

iTrader: (2)

Do you recommend grounding the 4-wire to the ecm over the engine block? Isn't the ecm grounded to the block making it the same either way? Thanks.

RBob

iTrader: (1)

Six of one and a half-dozen of another. On an EFI harness that already has the ECMs O2 ground connected to the block, I've been known to strip and fold over the sensor ground wire and hose clamp it to the sensor body. I've also been known to just use the 3-wire AFS-74 sensor.

If I were in the middle of modifying the harness, in this case I may change up the wiring and use the 4-wire sensor as it was designed to be.

Note that the ECMs O2 sensor ground is separate from the rest of the EFI harness grounds. It is dedicated to the O2 amplifier in the ECM.

RBob.