o2 readings, both narrow and wide band

[QuickSilverGSX9]

I had my car tuned on the dyno yesterday and came across two interesting facts. First off, my front o2 does not cycle properly, at idle, partial or WOT. I believe it cycled between .0 and .3 (and it never went above .3 volts, even during WOT). It never cycled anywhere near the .8-.9 range I was expecting. All this information was logged using ECU+.

The second issue, is that the wideband A/F went from a rich condition, to a lean condition in about 200 rpm's. It was a drastic change, with no fuel or timing being taken away or added. My hp and tq curves look great and did not suffer from this change in A/F (went from a 10.9-11.3 to a 12.3) I'll scan my dyno graph in later this afternoon. But, I'm concerned what would cause this huge change, my boost was rock solid (or so said my boost gauge), my timing was solid. Any ideas? Thanks guys.

-Bill

 

[Kevin Jewer]

The front o2 sensor is dead. It should cycle between roughly .2 and .8 in closed loop (it won't cycle at WOT or in open loop), and hold a steady high voltage at WOT, like .8-1v. I can't explain the change in AFR, but if it did not knock due to the change I am not terribly surprised the HP And TQ charts seemed to be unaffected.

 

[QuickSilverGSX9]

Thanks for the reply 95GSXracer. I fixed my problem, it turns out when we re-wired the alarm and stereo system (thre previous owner must've hired a 3rd grader to do this job), we swapped the ignition and front o2 sensor wires. Both wires are black with silver bands, so we just swapped them back, and now my front o2 cycles correctly.

Also, I'm attaching my dyno graph for whoever wants to look at it and see the change in AFR. However, it doesn't look too drastic on this graph, because this was after we made changed through ECU+ to enrichen it up top.

-Bill

You must be logged in to view this image or video.

 

[Kevin Jewer]

It seems too convenient that it happens right at 4500 rpm (O2 sesor will lag slightly because of it's location downstream from the motor, especially if it's in the tailpipe). Are you sure there is nothing funny in the tuning? Assuming 4500 is one of your breakpoints (never used ECU+). I know it seems obvious, and I don't mean to insult anyone by pointing out the obvious, but it doesn't hurt to double check.

 

[QuickSilverGSX9]

No insult taken. I've reviewed my settings (I can alter fuel/timing/airflow every 250rpm's with ECU+), and there are no changes at 4500 rpm's. I've added 1-2% fuel at 4750 up, to try and compensate for that lean condition, but, that's about it. Like I said earlier, no drastic changes in timing or fuel anywhere near 4500 to account for that AFR change.

-Bill

P.S.- I'm throwing a P1400 code, any idea as to what that means?

 

[Kevin Jewer]

That's odd, not sure why AFR would jump like that.

The P1400, doing a quick google search, refers to several different issues. For Mitsus, it's a MDP sensor malfunction.

 

[MyBeatGSX]

This might sound dumb, but is your AFPR holding pressure (if you have one)? Or maybe its the pump.

There isn't one jump on the chart, there's two. The rise at 2,700rpm looks identical to the one at 4,500rpm.

Just my observations....

 

[Kevin Jewer]

The dip at 2700 coincides with peak airflow/rev and is normal. This could be a fuel pump thing, but the rpm it happens at is very low and it does not rise linearly with increasing airflow/time, making it very unlikely. Still, especially since this is a stock pump according to the profile, rewiring it would be a very good idea.

 

[94Jettameowpsst]

Not thread jacking but you explained why my front o2 doesnt cycle and more than likely the reason my link is saying i have a "fuel trim malfunction" and its taking too long to switch to closed loop operation.