Ultragague questions - open loop, lean burn

[justjohn]

Hi, so I got an ultragague and I'm loving the real time feedback. However, I'm a little confused about what's going on with a couple things.

Fist is open loop. I only stay in open loop for ~10 seconds when starting the car. However it shows open loop after bump starts as well. Should I assume that's correct? Is it unavoidable then? (And would that negate most of the benefit of engine off coasting?)

Also, it seemed to pop on occasionally while cruising down the highway at 55 this morning, and always seems to go on when my throttle hits 35% or higher. I thought it wasn't supposed to trigger until ~80%?

Which leads to the next question: Throttle only seems to go from 9.41% to 86%. Is that normal?

Last is lean burn. I read you can tell lean burn by when the rear 02 drops to 0V. I drove in what I think should have been lean burn conditions for a fair bit today and saw it drop to .035 several times and .015 once, but never 0. Am I not getting there, or is "near 0" what was meant?

Thanks!

[justjohn]

Got it to hit .000 today. Seems more likely to enter when I'm going 60 than 45 though. Is that how it normally works? Didn't seem entirely predictable either, still a little confused.

Also, short fuel trim does not seem to correlate at all, and jumps around even more than rear 02 sensor. Should I just ignore it, or is there a way to get helpful info from it?

[justjohn]

Listening closely to the car it seems like .035 and lower is lean burn. Can't really confirm until I get an MPGuino though.

Can anyone else confirm?

[Phantom]

Okay lets see if I can answer most of the questions.

1. The car will enter open loop every time the car is started as this is part of the warm-up/start procedure. How long it stays in open loop depends on how cold the car is when starting and a few other things but temp is most of it.

1b. If you use the key to kill the engine it most likely cuts power to the PCM causing it to restart every time you bump start the car this uses a bit more fuel but if EOC long enough it should offset it. You could build an engine kill switch and that might keep it from going through the start procedure but you would have to test that or find some one with your car to verify.

2. Open loop will come on once a predetermined TPS% is reached this amount is different for each car. Also depending on the PCM programing the amount of load over a period of time can trigger the open loop.

3. "Throttle only seems to go from 9.41% to 86%. Is that normal?" No. The throttle should go from 0%-100% or very close. You will need to look up the TPS learn procedure for your car traditionally the procedure is something like this. 1. Key to on position throttle at 0% 10-15sec, key off. 2. Throttle 100% key on 10-15sec then key off. 3. Repeat step 1. When set correct it should give you readings from 0-100% this might help the lean burn and the point that TPS trips open loop.

4. The short term fuel trim (STFT) will jump around as it uses a formula calculate the % of fuel to add for a given reference table such as the MAF or RPMvsLoad. The STFT will adjust once the Precat O2 sensor goes over or under the predetermined value then once the PCM determines the STFT value is good it will save it to the LTFT. I do not know if this helped you or confused you but it is a start.

First thing I would do is make sure that the TPS is adjusted correctly.

[justjohn]

Thanks, I will look into setting the TPS.

[justjohn]

Manual doesn't have the procedure and it didn't come up when I googled it either. Tried what you said and a couple minor variations and that didn't seem to do anything.

Does anyone happen to know where I can find the exact method for a '96 civic?

[Phantom]

I'm not sure if your car has a learn procedure if it does not then you might manually have to adjust the sensor see How to cailbrate a TPS sensor.?????? - Honda-Tech