MaroonMonsterLS1

You really should log PCS amperage if you can
That's better than Duty

If the trans will make 220 in gear with the connector unplugged...and it'll only make 150 any other time...this is pretty well narrowed down to only a programming thing

dixiebandit69

Thanks for your input, Maroon.

I already checked the amperage with a Fluke amp-clamp over the wire, and the lowest the amperage got was .4-.5 amps.

What I can't wrap my head around is that this is a stock tune on a stock long-block.
The only things that have been changed are an LS6 intake, and LS1 manifolds. There's a cold-air intake, but it's still using a stock MAF sensor.

Besides MAP, MAF, and TPS, are there any other inputs I should check?

reubone

That is strange but I have seen it before. Commanded amperage never gets above .4 until the amperage table is modified or the torque model is manipulated. Pretty sure tuning could fix this.

dixiebandit69

I did some more testing a couple of days ago, to monitor the fuel trims. I figured if the fuel trims were off under full throttle, that might point me in the direction of the fault.
The fuel trims were dead on.
However, there is one thing I noticed: sometimes the MAF readings are lower than they should be.
Here's a full throttle pull where the MAF reading is high, and calculated load is 100%:




However, most of the time, the MAF number and load look like this:




Any idea what could cause this? If it was a bad connection, I would think that the MAF signal would just drop out completely. It's also worth noting that regardless of calculated load, I never got full line pressure.

Okay, but I still can't understand why this is happening if it's a factory engine and tune.

Was there some rare RPO code "FU0" that was setup for super soft shifts via lower pressure? Did GM have a hungover programmer who goofed the tunes one day?

I just don't want to got to some tuner, pay him $$$, only for it to be something small that I could have fixed myself.

cino

iTrader: (28)

At this point the best would be to make a test on another stock same year/model/options vehicle to compare. Maybe it is the way gm intended it to be and don’t ask why. Or simply tune pressure solenoid to your preferences.

FranksCustomTrans

Something that may already have been covered but in the tune pressure tables stock max line is set at 90 percent. So compared to harness unplugged you will see around 22lbs lower line.
You can raise to 99 for max. Dont go over 100 At least in my case I tried going over and pressure actually dropped , Bear in mind I am tuning on a 95 with obd1 Last year but from looking the tables for it and HP are not too different.

reubone

You could manually adjust the base line pressures up across the board by turning the epc solenoid screw. You could also unplug the maf and let the code set and run in speed density to see what that gives for pressure. I don't know passed that. If you can find someone with access to hp tuners, maybe you could borrow it and that would only cost you credits. we could help you dial in your tune.

dixiebandit69

Thanks for your input!

I did try unplugging the MAF a couple of weeks ago, and it still had low pressure.

I have messed with the EPC screw on another transmission in the past, but was told that it's a big no-no.

I know a guy with HP Tuners, and I plan to use it to try and figure out what's going on.