Occasional High Idle Speed - $8D 383 fully modified TPI

[JeepsAndGuns]

I can not speak for all of them, but on the 4 wire bosch sensor I used, the heater element wires were both the same color. In my case, both were white.

[zaut]

I got the three wire O2 yesterday. Two wires were black an the other was blue. The two black wires read 15 ohm between each and open to the blue and the O2 case. The blue read open to everything, like the old single wire O2 I was replacing. I connected the two black wires to the heater circuit and the blue to the O2 input. Everything is working fine. I have not been droping out of closed loop and have ajusted my closed loop timer to very short times and so far all is good.

[zaut]

On another area related to the O2 sensor. I kept the air injection system on the car. I see a scalar for Air Divert O2 rich/lean reduction in millivolts. Does this offset the point where the EMC thinks the AFR is when air is being pumped into the exhaust headers? If so, is there a way to determine if the value in the scalar is correct?

[RobertISaar]

yes, that's what it is for, essentially a correction since the O2 sensor is mounted after the AIR introduction point, so it will read the true AFR plus the external air being injected.

to correct it, if it's needed, i would tune the fueling with it off, then when you have that done, turn on the AIR system and then adjust that value until the fuel trims are back inline.

[zaut]

I did tune with the AIR, EGR,CCP etc. off. Thanks to the advice from EagleMark. Now that all the emissions equipment is turned on, I do see high and low BLMs compaired to what I had tuned to. Now that I have a heated O2 sensor, I am looking into that closer. By the way, the heated O2 is great. On hot restart, I am in closed loop in two seconds and about 30 seconds on a cold starts. What I am wondering is if there is a way to see the sensor output shift when the air is turned on. Once in closed loop, I would think that the ECM will adjust the AFR as soon as it sees the shift occure. My thought is to set the closed loop timer to a very long time and the scalar set to zero; start the car until the O2 is ready then cycle the air on and off and see the voltage shift. Would keeping the engine in open loop stop the AFR adjustment that you get in closed loop? Does this sound lake a good approch?

[RobertISaar]

i would assume staying in open loop would make the ECM stop accounting for it, but i haven't checked the hack to confirm it.

think of it this way, if doing it in closed loop, you can just watch the BLM/INT react to it and then just move the AIR value up or down to get them to return to their normal values.

[EagleMark]

AIR Pump is not used that often and only open loop, like cold starts for emmissions. Some were plumbed in after O2 sensor to add air to exhaust before the CAT for added heat, not sure if this type is open loop only? So what type does your car have? What type does the new ECM and bin have? I ask because I vagely remember an AIr pump system that did pump air during decel?

In Open Loop there is no fueling adjustment. Watch your BLM and INT should be 128. It runs strictly off VE table with no adjustment.

High and Low BLM changes will occur after a tune is done do to weather changes.

[RobertISaar]

having the AIR pump run before the O2 will actually help heat it up faster...

now that i think about it, that offset may be for entering closed loop, since to do so, the O2 voltage has to go so high or so low compared to 450mV.... perhaps it takes ~100mV away from that requirement?

[EagleMark]

Yes it would, but that was never the purpose of it. Just emmissions passed on to EFI from carbs and then phased out as not needed. Even 1995 LT1 came with Air Pump and was later removed as a factory service bulliten that caused issues but issues were not fixed because it was not needed. SO they got a plug in air inlet, relay removed and PCM re flashed with a TSB sticker.

Which would be an easier fix to disable it and leave it on if needed for astetics or emmissions visual check?

I've only done limited testing and research because of this. Testing at the time found it only working cold start. So it would never be found in an emmissions test.

[RobertISaar]

knowing what i've seen GM do....

is it generally active at coolant temps(startup or otherwise) from the ~65 to ~80 *F range? because that would allow it to run during the EPA city MPG test loop to get into closed loop faster. i've seen a lot of little things like this that were implimented to game the system.

[zaut]

My air system has two valves, one pumps air to the converter the other to both exhaust manifolds. If the only time it pumps air the exhaust manifolds is in open loop, I an not going to worry about its affect on closed loop AFR. I will disconnect the hoses tomorrow and run to see when I get air to the manifold. Since I am trying to keep it looking stock, I kept the system intact. Thanks guys for the great help.

[zaut]

OK, I tested the air valve to see if only applies air to the exhaust manifold only during open loop. It turns out to not be functioning correctly at all. The only port that air doesn’t get pumped through is the dump port. The AIR valve is bad, and most likely was when I tuned my VE tables. I plugged the line to the exhaust manifolds and now my BLM’s are running high. I think the air pumped into the exhaust was always skewing the EMC to run richer than it should. Now that the leak is plugged, the EMC has to adjust much leaner causing the BLM’s to go high. Does this make sense?

[EagleMark]

Yup! Hence my understanding and limited testing of the air injection is only used Open Loop. Just plug it and turn it off.

[zaut]

Yea, I read the service manual and it said it was only active in OPEN loop. But in my case, with a bad valve, it was pumping air into the exhaust manifold all the time. It is now plugged and turned off. Can I assume it is good to pump air into the converter all the time? I left that plumping intact.

[EagleMark]

Hmmm? I don't know? Does the manual tell when it usually works?