Code 32 with a high flow exhaust.

[PlayingWithTBI]

The only issue I noticed is after a second of sitting or going extremely slow, even after driving on the parkway, it immediately drops into open loop. Is there any concern with that or is it alright atleast for now to have that happen??

2 things can cause that...
1.) Your O2 sensor is getting too cold. This is another reason why I suggested the Heated O2.
2.) Some calibrations in factory .bins are set to go into Open Loop when stopped, usually <4 MPH.

 

[Road Trip]

Alright guys important update. I used field service mode and driving it was constantly perfect, equal between on and off flashes same duration.

Excellent! Solid feedback.

The only issue I noticed is after a second of sitting or going extremely slow, even after driving on the parkway, it immediately drops into open loop. Is there any concern with that or is it alright atleast for now to have that happen??

That's how others have said that the unheated (1-wire) O2 sensors operate, so this is expected
behavior, not a sign of having purchased a bad actor O2 sensor. I think Schurkey mentioned in
another thread that his single wire O2 sensor would do the same thing while waiting at a light, but
it would return to Closed Loop operation before clearing the intersection afterwards? But at the
same time others have upgraded to a heated '3-wire' O2 sensor as Stowburb (reply #12) and
PlayingWithTBI (reply #18) mentioned.

In response to another forum member expressing an interest in upgrading to a 3-wire O2 and using
the factory wiring method, I responded with the TBI-era factory wiring diagrams for the 4.3L which
went heated O2 in '94. (Heated O2 wiring) Probably not a huge upgrade priority for you given your
newly installed & properly operating O2 sensor, but something to keep in the back of your mind down the road.

Tomorrow I will shut the cutout and see in the morning if it pops code 32 (Ill try my best to meet the parameters to engage the ecm EGR test) later on in the afternoon I will drive again with the cutout shut in the field service mode and see fuel mixture with higher back pressure and see if it still drops into open loop at stops with more backpressure.

Good stuff! BTW, thanks for sharing what you are observing. This is something that we can refer back to if
helping others who can't get their Closed Loop to oscillate just above/just below the stoich level as it is
designed to do.

Safe travels --

 

[Road Trip]

2 things can cause that...
1.) Your O2 sensor is getting too cold. This is another reason why I suggested the Heated O2.
2.) Some calibrations in factory .bins are set to go into Open Loop when stopped, usually <4 MPH.

Thing #2 is interesting. I can't wait until I get to start wading around in the factory .bins like you've
been doing. (In a previous life all the listings for my computer system diagnostics were on microfiche,
alphabetized into a (full) industrial shoebox, and I kept my fiche viewer plenty busy reading listings
while on troubleshooting expeditions.)

I do remember trying to understand from the coders comments where in the data path is the bad logic when
the first 38 tests pass but the system halts at a particular memory address in Test #39.) Looking back, it feels
like I was a lot closer to Lincoln doing his homework with a piece of coal on the back of a shovel than how we do
things today... (Lincoln museum)

Brings back a lot of memories, most of them ungood. :0)

Thanks for sharing the wealth, it's appreciated.

 

[Road Trip]

I didn't mean anything derogatory. When I'm testing something I call myself crash test dummy. I think it's a term used more in the biker world.

Certainly not taken as derogatory. As a matter of fact I used this same phrase in a similar fashion with another forum member
back on Feb 24th: (Crash Test Dummy)

No worries, we're all pulling in the same direction -- it's one of the things I like about this forum.

Cheers -

 

[Nick88]

interesting feedback about my o2. I originally thought it was getting too cold, but the under 4mph reason may be more realistic. I think i forgot to mention but pretty much the same second I hit the gas out of the stop it kicks into closed loop. I guess we will see tomorrow afternoon with cutout shut if it immediately drops out or if it stays in for a bit before dropping into open loop. very curious

 

[Schurkey]

The '88 TBI/Emissions service manual says the small-block (and V6?) O2 sensors should still be active (allowing closed-loop operation) at idle. The 454 will go to open-loop at idle, though.

My own '88 5.7L used to drop out of closed-loop at idle. Just like yours, it was back in closed-loop before I could cross the intersection after a stop light. I replaced the O2 sensor. Haven't checked it for a long time...I don't know if it's staying in closed loop at idle now.

 

[Nick88]

update- just took the parkway with cutout shut, much more peaceful quiet drive as everyone can probably imagine. More importantly I did not get a SES while holding it around 50-55 the whole time with almost no movement of the pedal. Obviously this isnt 100% conclusive as maybe somehow today it passed but tomorrow it wont. either way later I will drive in field service mode with the cutout shut and report back to everyone

 

[Nick88]

Forgot to update again yesterday, but I drove in field service mode with cutout shut. The fuel mixture was pretty much the exact same, but interestingly the truck still dropped out of closed loop immediately anytime Id stop, I'm not too concerned though as based off of the blinking of the SES in field service mode, it seems to be reading correctly and making the engine run correct.

 

[GrimsterGMC]

Having it go into open loop just at idle can be beneficial if you are having trouble with a rough idle, so not really something to be too concerned about as it goes closed as soon as you start rolling again.

 

[Nick88]

Having it go into open loop just at idle can be beneficial if you are having trouble with a rough idle, so not really something to be too concerned about as it goes closed as soon as you start rolling again.

Yes once I start rolling it immediately kicks back into closed loop.