Tuning my 3500!

[PCGUY112887]

OK, back to stock file, on my 4th MAF modification, PE set to 45% across the board... some of my O2's are WEIRD. Full throttle and an o2 reading of 52.08, others (most) have a reading of 600-800. The o2 sensor is brand new.

Wideband showed 14-15:1 while WOT again.

What in the hell is wrong here? I haven't upped the MAF anymore, maybe I should up it another 15% over 7k hz?

http://www.theopia.com/o2scan.zip

[Superdave]

wow.. and i thought i had it rough with OBD1.. looks like i know what i'll be staying with..


We tuned my PE mode first, kept changing the BPC to get the wideband AFR's into the high 11's/low 12's at WOT. Now that i'm making decent power at WOT i've started backing off the VE tables below 90 MAP to get my BLM's to 128.


Remember.. being rich is always better than being lean

[PCGUY112887]

Yes and I could just massively edit my MAF table, but it seems such a crude way to tune...

Also how can I change A/F ratio in open loop startup? For some reason it starts fine, stays around 14-15:1, then goes super lean for a few moments and stumbles then it goes into closed loop and goes back to 14-15:1?

[PCGUY112887]

Anyone?

[PCGUY112887]

Oh no! Everyone forgot about me!

Still the same situation, and as mentioned earlier for some reason when it's just coming out of open loop it goes super lean and the engine chugs like crazy, then a moment later (when it hits closed loop) it's fine.

[3400-95-Modified]

Hrmm... kinda got me stumped here... I havent had a issue yet with mine... I dont know what could be happening with yours.

[PCGUY112887]

Humm who else is a 3x00 expert on here/the powrtuner forums?

I want to just add all kinds of MAF to get it to stay a good AFR at WOT but it just doesn't seem right.

[3400-95-Modified]

Its not right and you shouldn't need to do that.

There is something else wrong somewhere and I just cant put my finger on it... With 100% stock tables in my Venture bin I will get 830's on my O2 at WOT with out question.

Something else is amiss here and I'm not quite sure what.

[3400-95-Modified]

I need to see one of your scans...

I want to see

TP%
TPv
A/F <--Commanded Not your wideband input.
O2 mV (narrowband)
MAP kPa
MAF
Spark
Injector PW
FT cell
STFT
LTFT
IAT
RPM
Current Gear
KR
ECT

Then I can tell you what may be going on.

For an example, I just attached one of my scans from today. Notice my O2 mV levels when I'm at WOT... there is at least one point in that scan where I did a little pull.

[PCGUY112887]

Sorry, no updated scans yet... just about all of that info was in my last scan that I posted however.

I did find something yesterday that may explain a bit of the issue. The emissions hose that runs from the rear valve cover to the intake hose, well the tube came out of the valve cover (since it's gay and won't stay in) and it was sucking a ton of air in, air that never gets registered by the MAF since it's after the MAF.

Soo to me extra air + the computer not knowing about it = lean?

What would happen if I just put a breather on the rear valve cover and got some different pipe instead of the flex hose?

[IsaacHayes]

That will work. That's all the rear cover is is a breather. The front is PCV that goes to the plenum so no problems there. Funny my rear cover breather pipe would always pop out when the motor was stock, then after the 3500 plenum swap it fit perfect and stayed in!

[PCGUY112887]

Would I sound crazy if I said I noticed my oil pressure gauge reading higher after I plugged that hose back into the rear valve cover?

About 5psi higher.

[IsaacHayes]

Yeah, you are crazy!