Mikeymx5

iTrader: (2)

My car runs great, but for one thing...

When Im cruising in first or second gear at very light throttle my car likes to buck only some times. Doesn't happen all the time but often enough to be annoying.

Can also happen on the freeway when cruising in mid RPMs.

Wide band shows the car will jump lean then rich in a quick blip. Anyone had this problem and what part of the map can fix it with out messing up my other wise well tuned AFRs.

2003 begi S2 2554, 550cc, xede

psimiata

mine did the exact same thing. Wideband shows stoich and then at almost no throttle input jumps to 16.5 and back to stoich. Look for some points on your maf map around were your o2 switch or o2 signal takes over. I added a little fuel around 50-55% and 3000-4000 rpms.
One of the things I did that really helped was to remove (zero) the o2 map so the car never listens to it. Drive a little like that and you should be able to find the lean spot.

Mikeymx5

iTrader: (2)

I was thinking of disconnecting the 02 that sounds alot easier to do.

psimiata

I believe I posted incorrectly anyhow. With my o2 map ,I had to fill the whole map with -10.5 to keep it from going stoich during cruise. Disconnecting the o2 will give a code and I'm not sure what the base map will fall back to. Good luck

Stephanie Turner

Add fuel. the car is lean.
Stephanie

Stephanie Turner

That is a REALLY BAD IDEA! Unless I am very confused as to what you did.
Only the top half of the O2 map needs to read -10. That sends the car open loop. The zeros leave the car in closed loop.

Stephanie

Stephanie Turner

That is also a REALLY BAD IDEA! You need the O2 sensor in the car. And the Xede needs to control the O2 sensor in order to send it open loop under boost.
Stephanie

Mikeymx5

iTrader: (2)

I never tried it, I was just wanting to know if the problem was the car jumping in and out of closed loop, but my obd2 reader is to slow to catch all the activity. I assume if the car gets an o2 error code it will ignore the 02 for closed loop and force it to stay open.

Any way Im off doing tuning of other sorts with other problems now, but probably will re look into this later so that I can help out others that have the same problem.

Stephanie Turner

It depends on the O2 Code. If it is an O2 stuck rich, yes it will run open loop all the time. It has been my experience with my OBD II reader is if the fuel trims and O2 voltages are slow to react, it is a stuck O2 sensor. It may be a bad sensor, or it could be a bad O2 map.

Below are two O2 maps. The first one is a bad map. It has positive and negtive numbers in the O2 map. It is ok to modify the O2 map in the Idle area if needed. But only as a last resort.

The second map is how it should look. The load value of 30 is about where the car hits boost. So that is about where you want the -10 values to start.

If you map looks like the first one - the car will go open loop when on the -2 and -7 cell. Open loop at cruise is a gas guzzler. The postive 2 number probably would not do much, but the positive 7 number will make the ECU think it is lean.

Hope it helps.
Stephanie