New 3 bar OS wont idle, surges and dies

[jake.]

Hello all, new to the forums here. Anyhow just got my truck together, 4.8, 220 cam, 80e, SD80's, E85, 7875 turbo, dual walbro 450's. I flashed the 3 bar OS today before i tried to crank the truck for the first time since starting on the turbo. It will fire up, idle surge bad until it finally dies. The fuel pumps are staged (one on a hobbs switch) and with one pump i am showing around 65-70 psi (kind of high?) when it acts like it wants to idle. WB is fluctuating about .75-1.00 lambda then rises lean around 1.30 or 1.40 before it dies. I am using a cheap 3 bar map sensor from efisource, shows 105kpa at koeo, and shows around 70-80kpa at idle (seems high to me?). I just checked a log from earlier and it is even showing about 102kpa at 1000rpm idle. I have tried adjusting the ifr for the increased fuel pressure, and i have also found when i changed to the the bar os my ve table was screwed up, so i fixed those values according to my old tune. For reference the truck ran great on the same injectors, E85 and cam on the standard OS. Only change fuel wise was the map sensor and the fuel pumps.

edit: this tune is set up OLSD, no O2 sensors

[GMjunkie]

I am in no way a seasoned tuner but, what was your fuel pressure before the pumps? Could you be putting so much fuel to the front of the vehicle that the return line can not return all of it? You should be able to watch at least the stft to see if the ecm was trying to pull gobs of fuel out right? Wonder if you could also try plugging the original map sensor back in to see what it will idle like? Like I said I am in no way a seasoned tuner. Just thoughts. I am getting ready to do the same basic idea. Turboed 5.3

[5FDP]

Possible the cheap non GM map is the problem. I'd much rather prefer a good MAP sensor with known good linear and offset settings for the tune.

Post the tune if you can too.

[mowton]

Post your tune....did you delete the single bar map and MAF AFR Channels and add the 2 or 3 bar map channel? Add the 2 or 3 bar parameter to your Chart/Graph and set max to highest level you expect to see. Did the Map sensor come with scalar data? What is the part number? Will the idle stay if you feather the throttle, if so add some RAF to start with. In order to tune the idle, you should get the MAF and/or VE dialed in and then work down towards the idle rpm area's.

Ed M

[jake.]

4.8 E85 3 BAR SD test.hpt

I forgot to change the map channel to the 3 bar so I will do that now and see what kind of readings im getting. The scalar data I used was from efisource's website (305 and 10.33). Its the GM style 3 bar map they sell with the nipple in the middle of the sensor. I didnt check the fuel pressure before but it was stock pump/stock rails with the rail mounted regulator. The truck dies as soon as I touch the throttle.

[mowton]

Post a log. Read your DTC's. Do you have a check engine light and a p0101-0103 fail? Normally the DTC's need to be set to Fail on first error and leave the SES checked so you can see the fail over to SD.

Ed M