400E Warm Idle bump

[Oldcar]

Run with 02 sensor disconected to test if warm idle bump goes away?

 

[Oldcar]

Would plug back in be the reset for the o2 and lh? I was told wire plug connect is under passenger carpet.....gsxr would know?

 

[gsxr]

Would plug back in be the reset for the o2 and lh? I

Nope, only way to reset LH adaptation values is with a hand-held blink code reader, or digital scanner that can speak to the LH.

was told wire plug connect is under passenger carpet.....gsxr would know?

The O2 connector for V8 models is underneath the car in the driveshaft tunnel. There is nothing to disconnect under the passenger carpet (that's for 6-cyl engines).

 

[Oldcar]

So clear which pin to reset o2 with lh ?
If I understand correctly unplug and plug back in sensor conect under car is of no benefit?

 

[gsxr]

So clear which pin to reset o2 with lh ?

To reset via blinker box, first check & clear codes on pin 4 (LH module), then "clear" the single blink as you would normally clear other codes. This resets the adaptation to mean values. It's documented in the DTC code PDF file, in the fine print that nobody ever reads. However you cannot verify that the adaptation values have been reset to 1.0004 [mean value] without a digital scanner, which will show the adaptation values (i.e., 0.9xxx or 1.0xxx).

If I understand correctly unplug and plug back in sensor conect under car is of no benefit?

Correct. All this would do is verify the connector is properly seated. It's a twist-lock, and if not rotated fully past the detent, there may be no signal from the O2. This would normally trigger a fault code on pin 4 and also turn on the CEL if the car has a CEL (with a code on pin 19 / DM also).

 

[Oldcar]

Thanks gsxr!!!

 

[Oldcar]

To reset via blinker box, first check & clear codes on pin 4 (LH module), then "clear" the single blink as you would normally clear other codes. This resets the adaptation to mean values. It's documented in the DTC code PDF file, in the fine print that nobody ever reads. However you cannot verify that the adaptation values have been reset to 1.0004 [mean value] without a digital scanner, which will show the adaptation values (i.e., 0.9xxx or 1.0xxx).



Correct. All this would do is verify the connector is properly seated. It's a twist-lock, and if not rotated fully past the detent, there may be no signal from the O2. This would normally trigger a fault code on pin 4 and also turn on the CEL if the car has a CEL (with a code on pin 19 / DM also).

Noticed improvement after pin 4 reset

 

[emerydc8]

What do you mean by warm idle bump? Is it like a hiccup or momentary stumble? If so, how often does it happen?

 

[Oldcar]

Happened only when warm ocasional hiccup at idle. Pin4 reset may have cured it. Purpose was to reset o2 to lh.....if it happens again may have to gap plugs at 1mm or .40inch

 

[emerydc8]

That is exactly what I am getting, When warm and idling it hiccups every few minutes for a fraction of a second and then it goes back to idling as smooth as glass. I have the gap set at 1mm on my plugs. It's not something I would spend a lot of time looking into unless it gets worse but so far it hasn't. There is no issue with it off-idle or even when cruising at a constant speed on the interstate. I'm wondering if it has anything to do with opening and closing of the thermostat because it always seems to happen between 80C-85C. But I don't know if that is even possible.

 

[Oldcar]

Gsxr told me how to do pin 4 lh reset and the issue of warm idle bump is nearly gone....it resets o2 senor as well think o2 sensor FB to lh was most of the problem just see above!

 

[emerydc8]

Thanks, @Oldcar. I’ll check it out. I just realized I have to run the car through emissions tomorrow and resetting the adaption could affect that so I’ll have to wait until afterwards.

 

[Oldcar]

Correct code clearing prior to e test may cause reject

 

[emerydc8]

Well I failed the HC part of the emission test—333 vs. an idle standard of 220. There was too much traffic and I didn’t have space to drive to the test facility at 4000-5000 RPM, plus I drove it directly to the facility from a cold start. This has happened before when I’ve done this and a bottle of GTP and making sure the aftermarket high-flow cats are hot prior to testing has been the solution.

Since I won’t test until I run through a full tank of gas I decided to reset the LH adaption on pin 4 as per the @gsxr technique. Then I decided that I would just swap out my LH module with a good spare. I reset the LH adaption on the new one too so we’ll see if it resolves the warm idle bump. I’m not optimistic.

 

[Oldcar]

Thanks, @Oldcar. I’ll check it out. I just realized I have to run the car through emissions tomorrow and resetting the adaption could affect that so I’ll have to wait until afterwards.

 

[emerydc8]

Update: The new LH module didn’t help the idle bump. I installed the old module and reset the adaption on pin 4 but I doubt it’s going to do much if another LH module didn’t fix it. We’ll see. I haven’t driven it with the reset old module yet.

 

[Oldcar]

You may possibly be suprised

 

[Oldcar]

To reset via blinker box, first check & clear codes on pin 4 (LH module), then "clear" the single blink as you would normally clear other codes. This resets the adaptation to mean values. It's documented in the DTC code PDF file, in the fine print that nobody ever reads. However you cannot verify that the adaptation values have been reset to 1.0004 [mean value] without a digital scanner, which will show the adaptation values (i.e., 0.9xxx or 1.0xxx).



Correct. All this would do is verify the connector is properly seated. It's a twist-lock, and if not rotated fully past the detent, there may be no signal from the O2. This would normally trigger a fault code on pin 4 and also turn on the CEL if the car has a CEL (with a code on pin 19 / DM also).

Warm idle bump gone
...car runs so smooth its (almost) boring!

 

[emerydc8]

You may possibly be suprised

I installed my original LH module and reset adaption. The warm idle bump has now been replaced by an idle surge. It happens about every minute and only with the car in D or or R. The surge frequency is about two per second and amplitude runs between 450 RPM and 550 RPM. It has been auto-correcting so far and smooths itself after about five seconds, but will return after a minute to do the same thing. Taking the car out of D or R stops the surge immediately. I hope this is just part of the LH adaption process but it has lasted several days now. I think I need to start looking for another LH module.

 

[Oldcar]

To reset via blinker box, first check & clear codes on pin 4 (LH module), then "clear" the single blink as you would normally clear other codes. This resets the adaptation to mean values. It's documented in the DTC code PDF file, in the fine print that nobody ever reads. However you cannot verify that the adaptation values have been reset to 1.0004 [mean value] without a digital scanner, which will show the adaptation values (i.e., 0.9xxx or 1.0xxx).



Correct. All this would do is verify the connector is properly seated. It's a twist-lock, and if not rotated fully past the detent, there may be no signal from the O2. This would normally trigger a fault code on pin 4 and also turn on the CEL if the car has a CEL (with a code on pin 19 / DM also).

Warm idle bump gone
...car runs so smooth its (almost) boring

I installed my original LH module and reset adaption. The warm idle bump has now been replaced by an idle surge. It happens about every minute and only with the car in D or or R. The surge frequency is about two per second and amplitude runs between 450 RPM and 550 RPM. It has been auto-correcting so far and smooths itself after about five seconds, but will return after a minute to do the same thing. Taking the car out of D or R stops the surge immediately. I hope this is just part of the LH adaption process but it has lasted several days now. I think I need to start looking for another LH module.

Ideas
1. maybe reset new lh module and check
2. send worst lh module to alphasud to repair if bad.
3. Check for vacum leaks particularly trans vacum line on top of intake manifold

Did you test car and drive it on highway?
Unusual issue occurs only in dr or rev?
For me hunting idle happened in neutral and park only a few yrs back and was gone. It was not a big problem
Hunting idle may br LH trying to adjust to compensate for a vacum leak or some other problem.






.

 

[emerydc8]

This is strange. In the process of troubleshooting the warm idle bump I swapped LH modules and the idle surge started. I pulled that module out and re-installed the original. Now I have an idle surge with that one too. I no longer have the warm idle bump; so I fixed one problem and gained another with the same module. Go figure.

The surging idle only happens in D and R. If I put it in N or P it dampens out within one or two cycles. I did reset the LH module when I installed it back in the car last week. If it was a vacuum leak I think it would have been doing this with the other module.

I guess I can try to reset the adaption again and see what happens.

I did have an idle surge years ago but only when the outside air temperature was below 70F and I don't remember if it was with this LH module or the other. In any case, it went away at some point and I never determined the reason.

When I pulled the codes last week I did get a code for a short in the IAT sensor and I cleared it. If that is there again I'll order a new one, although that never seems to be the fix.

 

[emerydc8]

Ideas
1. maybe reset new lh module and check
2. send worst lh module to alphasud to repair if bad.
3. Check for vacum leaks particularly trans vacum line on top of intake.

Good idea. DM sent to @Alphasud40