16197427, $OE, AMC 401, Oxygen sensor goes super rich does not move

I am just barely getting my rig on the road after installing this TBI and rebuilding my engine. Throttle body is a 454 unit with the 74# injectors. Engine is freshly rebuilt with mild street cam and mildly ported heads, Edelbrock dual plane intake, long tube headers, and the oxygen sensor is in the drivers side header collector (it's a 4 pin O2 sensor, is hooked up with keyed 12v to the heater element and both output grounds connected together).

I sent my injectors out to be cleaned and flow tested before my build and they were verified to flow correctly. My fuel pressure is at 12psi (I have a gauge on my return line). In my BIN, I have 74 in my "Injector flow rate (TBI lb/hr)" scalar and have inputted my Cylinder volume (50.88 for my 407cui) scalar. Oxygen sensor is new to the install and I have about an hour run time on it. I have smoothed my closed loop open throttle table but have not messed with any other VE or timing tables. I have had idle set at both 750 and 650.

When I start my truck it fires RIGHT up and settles into a nice even idle in open loop (warm or cold). My O2 sensor gives me the expected 490mv. As I start to warm up, I hit closed loop pretty quickly but my O2 sensor is still hovering around 490. As I hit the road it feels great. About a minute later the O2 sensor quickly swings to 1090mv, the engine starts to bog/lose power, BLM goes from ~122 to low 80's, it feels like I am out of gas unless I give it enough throttle to hit AE, then I trip a code 45, go open loop and the truck runs great'ish with BLMs hovering around 122. My oxygen sensor then stays at 1090mv for the rest of the drive.

Should I assume I really am super rich? I have a single wire O2 sensor I could swap on but I really don't want to cut the connector off just to throw a part at my truck. What would you guys do? I am also getting a Code 35 after I warm up but am assuming that is not related because that "should" cause me to lean out more than get rich and it is not consistant.

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Originally Posted by rang-a-stang

I am just barely getting my rig on the road after installing this TBI and rebuilding my engine. Throttle body is a 454 unit with the 74# injectors. Engine is freshly rebuilt with mild street cam and mildly ported heads, Edelbrock dual plane intake, long tube headers, and the oxygen sensor is in the drivers side header collector (it's a 4 pin O2 sensor, is hooked up with keyed 12v to the heater element and both output grounds connected together).

I sent my injectors out to be cleaned and flow tested before my build and they were verified to flow correctly. My fuel pressure is at 12psi (I have a gauge on my return line). In my BIN, I have 74 in my "Injector flow rate (TBI lb/hr)" scalar and have inputted my Cylinder volume (50.88 for my 407cui) scalar. Oxygen sensor is new to the install and I have about an hour run time on it. I have smoothed my closed loop open throttle table but have not messed with any other VE or timing tables. I have had idle set at both 750 and 650.

When I start my truck it fires RIGHT up and settles into a nice even idle in open loop (warm or cold). My O2 sensor gives me the expected 490mv. As I start to warm up, I hit closed loop pretty quickly but my O2 sensor is still hovering around 490. As I hit the road it feels great. About a minute later the O2 sensor quickly swings to 1090mv, the engine starts to bog/lose power, BLM goes from ~122 to low 80's, it feels like I am out of gas unless I give it enough throttle to hit AE, then I trip a code 45, go open loop and the truck runs great'ish with BLMs hovering around 122. My oxygen sensor then stays at 1090mv for the rest of the drive.

Should I assume I really am super rich? I have a single wire O2 sensor I could swap on but I really don't want to cut the connector off just to throw a part at my truck. What would you guys do? I am also getting a Code 35 after I warm up but am assuming that is not related because that "should" cause me to lean out more than get rich and it is not consistant.

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I would start by correctly wiring your O2 sensor. The O2 sensor heater and signal should not share a single ground. The sensor ground should be hooked directly into the PCM O2 signal ground connection. The pin for the 02 sensor signal ground (not heater circuit) should be A12. From the factory that wire should be Tan and hook to the engine via an eyelet. I would properly ground the 4 wire sensor before converting back to a 1 wire.

Ok, will do. that makes sense.

Remember out txt conversation lol
Gotta make sure everything is "right"...
Good to see you're making progress though! You'll get it done.

And check this thread
http://theamcforum.com/forum/ls-rockers_topic67165.html

LS 1.7 rockers are doable!

Yep! Getting much closer. My truck cruises super nice, but still working some bugs out. I probably won't touch it for a couple weeks to appease the wife but I am close!

That is AWESOME!!! I wish I would have seen it about 6 months sooner though!!!

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Originally Posted by Fast355

I would start by correctly wiring your O2 sensor. The O2 sensor heater and signal should not share a single ground. The sensor ground should be hooked directly into the PCM O2 signal ground connection. The pin for the 02 sensor signal ground (not heater circuit) should be A12. From the factory that wire should be Tan and hook to the engine via an eyelet. I would properly ground the 4 wire sensor before converting back to a 1 wire.

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When I look at the wiring diagram I see A12 as the O2 sensor ground, like you said, and I have A12 grounded. But should I have the sensor ground pin connected to A12? or should I ground the sensor ground at the same place as the tan eyelet?

Right now I have 12V and ground to the 2 heater wires, Purple is going to O2 signal (A10). Not sure where I should stick the Sensor ground...

Any good ground will work.
Once a wire is connected to ground it is "tied" together with anything else grounded.
On mine I simply connected ALL the ground eyelets to a single bolt on engine.

That's what I did, too. it's also the same bolt that my battery ground is connected to.

So when I go back to tinkering (maybe Friday) I will run a dedicated ground from the sensor to the bolt. I know my A12 is grounded but I am not sure it if is a dedicated ground or tied into the other ground wires. If it is tied into other ground wires, I will separate it and run a dedicated ground wire to that same bolt, too.

is this a new sensor or used?
they do go bad sometimes.

Brand new to this install. Efi side connector from a wrecking yard, though. Maybe I’ll go 3 wire? That should be an easy swap from where I am right now.... hmmmm...

OK, progress.

First I ran a dedicated ground from my ground bolt to the O2 sensor ground. Fired it up and I went to closed loop idle pretty quick. When it was cold, it idled amazing. Then, all the sudden the O2 sensor started swinging from 50mv to 1100mv, wildly/quickly. So I shut it down and connected A12 to a direct/dedicated ground just like the oxygen sensor output. Same result (swinging O2 sensor). I didn't have time to tinker much more and did not take it for a ride. If I rev it, seems to have good throttle response but also has a bit of a backfire in there.

What should I do next?

Ok, all done! Had a bad rotor in the mix. O2 sensor works great now, and the truck runs well! On to tuning! Thanks everyone!

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Originally Posted by rang-a-stang

My fuel pressure is at 12psi (I have a gauge on my return line).

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You need to double check this. Your gauge should be on your supply line and you should not have 12psi on your return.