Engine goes mega lean when it enters closed loop

[rindoze]

I got the O2 bung welded into the collector now. Unfortunately the AFRs are still reading lean. It really doesn't make any sense to me. The majority of cells want fuel, but sometimes adjacent cells say they have too much. I cannot understand why it keeps reporting that it wants more fuel at idle when idle is reading pig rich the majority of the time. I added a good bit more to the VVEs again, and this time at least the misfires are not showing in the log, but it really starts stumbling worse off idle each time I add more. L28SD2.hpt o2move+10+10+more.hpl

[edcmat-l1]

It's lean everywhere. My suggestion is stop second guessing the data and dial it in. See how it runs once you've got the trims under 10%.

I would also throw a fuel pressure gauge on it just to double check. Because you know, it only makes sense.

It's not an O2 problem as you mentioned in your previous post. The narrowband is working fine.

VSS is reading 158 constantly so I'm assuming it's an auto OS. Not sure if that has any bearing on what's going on.

[rindoze]

It's lean everywhere. My suggestion is stop second guessing the data and dial it in. See how it runs once you've got the trims under 10%.

I would also throw a fuel pressure gauge on it just to double check. Because you know, it only makes sense.

It's not an O2 problem as you mentioned in your previous post. The narrowband is working fine.

VSS is reading 158 constantly so I'm assuming it's an auto OS. Not sure if that has any bearing on what's going on.

I'm getting a fuel gauge now. According to the histogram yes its lean everywhere, but looking at the real time log anywhere its idling its rich. Is it hptuners generating these histograms? Perhaps VCMScanner is messing up something?

richIdles.png

[edcmat-l1]

I'm getting a fuel gauge now. According to the histogram yes its lean everywhere, but looking at the real time log anywhere its idling its rich. Is it hptuners generating these histograms? Perhaps VCMScanner is messing up something?

richIdles.png

OMG stop trying to over analyze it.

The beginning of the log the idle was adding fuel, positive trims. It wasn't until later in the log where it started pulling fuel at idle. Again, need to check the pressure. Not just a static check, but put a gauge on it you can read from the driver's seat while operating the vehicle.

Dial the thing in using the data. Then, once the trims look normal everywhere, if it has any kind of driveability issue, address that as a separate issue.

50 seconds into the log it's still adding 18% or so. It's not until about a minute later that it starts pulling fuel at idle. Because it's already embedded the trims in the histrogram, it'll then take a lot more cell hits for it to then chart the negative trims. If you stop the scanner then start it again, it will plot the negative trims in your idle area.

50 seconds.jpg

[rindoze]

I've stopped and started the scanner 6 times today, its always the same, it says it wants more fuel at idle. I've tried doing this the normal way, I keep adding fuel but the histogram doesn't improve. I get to a point where I've added so much fuel the car doesn't want to crank and is stinking. How is it that a few seconds of "supposed" lean on startup (when the O2s shouldn't even be used) leads needs like 60x the hits of it reading rich before it starts trimming STFT? If you look at the data its actually increasing the LTFT of idle the longer it goes. If I follow the data the car runs worse. I don't trust the data.

[edcmat-l1]

OK then good luck to you.

[GHuggins]

This might be a stupid question, but you are giving it about 20 minutes of run time before logging for fuel corrections after flashing aren't you? Then I never saw any of the previous questions answered, so Is the Nissan engine built like the GM as far as the variable cam controls goes? Are you using the GM O2 sensor? Is it only lean on startup?

[rindoze]

Its a single OHC engine. I disabled variable cam in the OS. I'm using all the GM engine management parts including O2s. Most of the time I am only waiting a couple minutes after flashing to start logging. Its lean according to the scanner all the time, which makes me hesitant to go on longer drives. Also the laptop I have for logging lasts maybe 10 minutes before the battery dies.
Looks like the battery I had in the car just crapped itself it was a li-ion one. Maybe I'm lucky and a new one clears some of this up.

[LS ROB]

Are you resetting fuel trims every-time before logging? It may not be that this is happening to you; but I have noticed on my gen4 e38, that if i reset fuel trims every time before logging, then it takes a lot longer for the trims to level out to where they make sense; meaning more cell hits required. I do not reset fuel trims every time i log. This is my opinion only, but if you reset fuel trims and take a 15 minute drive, chances are the trims do not have time to count down/up so you will always be overshooting your fueling.

[rindoze]

This is pretty much wrapped up now. Fuel pressure was checked and is dead flat 80 psi all times(I'm running off the internal pump regulator for a camaro). The exhaust gasket had some leaks, had to buy an expensive remflex one to solve that. With that changed idle started showing rich, but still lean everywhere else. Next the Holley 2.5 bar MAP I was using is either defective, crappy, or the specs on it are wrong. Its Holley 870021, which is supposed to be identical to the GM # 12592525 sensor everyone uses. I used the offsets for that. I put in the factory 1 bar MAP sensor and my oh my did the logs change. Rich rich rich rich, everything rich, vacuum readings much different too. Sadly I can't let the car go into boost with this MAP sensor so I'll need to replace it. Once that is done all this should hopefully be behind me.

[gtstorey]

I think the only part of that MAP sensor that is same as the GM MAP is the physical size.
https://forum.hptuners.com/showthrea...l=1#post701037

[edcmat-l1]

Just an FYI, observation, if you're at sea level (close anyway) the MAP is functioning as it should. That being said, not sure why you'd use a Holley MAP sensor that is supposed to replace a 12592525 instead of just using a 12592525.

[rindoze]

Just an FYI, observation, if you're at sea level (close anyway) the MAP is functioning as it should. That being said, not sure why you'd use a Holley MAP sensor that is supposed to replace a 12592525 instead of just using a 12592525.

Because I buy from Amazon and its half the price. The GM one has so many Chinese counterfeits that you may get a fake one. Holley tech support told me it was the same settings, I asked them straight up if I put this in my ls9 if it will work without modification and they said yes. That plus when I set it up with the gm 3 bar settings it showed 100kpa with the engine off as expected made me think this was true.

[edcmat-l1]

Because I buy from Amazon and its half the price. The GM one has so many Chinese counterfeits that you may get a fake one. Holley tech support told me it was the same settings, I asked them straight up if I put this in my ls9 if it will work without modification and they said yes. That plus when I set it up with the gm 3 bar settings it showed 100kpa with the engine off as expected made me think this was true.

Yeah but half price is 25 bucks. Why would you want to give yourself a headache over saving 25 bucks.

Either way, that's not the cause of your issues. The exhaust leak might be, but not the map sensor.