Turbo 6.0, having trouble with GM 3 bar map + tune

[steve70]

Hey guys, I am running an 01 6.0 lq4 with gen 4 rods/ pistons in my el camino. I have just gotten it running with a GM 3 bar map sensor (12592525), and from my research I see that it's MAP linear should be 312.50 KPA and offset at -11.35. I can not get that to work. the only way I can make the car even attempt to run is by skewing the offset to +18 KPA, and runs best at +25 kpa. However obviously as soon as I try to drive it, it quickly goes into boost enrichment and goes pig rich and runs like garbage.

It is running the 1253012 2 bar Speed density OS. Deka 80lb injectors, walbro 450lph pump, 31x12x3" intercooler and a 78/75 single turbo.

I don't want to get into messing with the VE to fix fueling because I feel like that's a bandaid for the MAP offset being so far off. Does anyone have any thoughts on why I can't get the car to run with the proper MAP data?

I am trying to figure out how to upload my tune in case that may help diagnose the issue.

Thanks in advance, Steve

[5FDP]

New bad MAP?

Is the wiring right?

Have the tune handy, maybe another setting isn't right and causing problem.

[steve70]

I did have to change the wiring between the stock truck and ls9 map, I think i have it right. With the key on, but engine off it reads 0kpa though which seems strange to me. Im trying to figure out how to upload my tune file.
I have it wired that pin 1 is 5v reference (gray), 2 is low reference (orange/black) and 3 is map signal (green).

[2xLS1]

Should not read 0 with KOEO. Should read atmospheric pressure somewhere around 95-105 kPa depending on altitude and barometer.

[mightyquickz28]

I had a bout of similar problems with my first 3 bar MAP sensor. I bought it from the classifieds on ls1tech.com and the AC Delco part number was 12623671 stamped on it. I found the Offset and Linear and plugged those it. Just like you stated, I had to really try a bunch of different values to get it to even start but if I put it in gear, etc, anything to 'load' the engine, it would stumble and die. Just pressing the gas in neutral got all kinds of backfires.

Searching the internet for days, I found somewhat of a consensus. (a) Most tuners that referred to that particular MAP sensor didn't find it reliable and (b) that they opted to get their 3 bar sensor from EFI source. Running out of patience, I ordered the EFI Source sensor. Plugged in the indicated Linear and offset.Vroom! Started up and rev'd fine. Been working great ever since. (over a year)

Also, with the MAP sensor hooked up and key on, engine off, your scanner should read approx. 104 kpa if the Linear/offset are correct. Certainly zeros is a bad sign.

What version of HP tuners are you utilizing? I just found an old thread that indicated the earlier versions of HPT (ver 2.24 and earlier) did not allow tuners to enter negative values in the offset field. Zero was the minimum at that time. It was corrected quite awhile back. (2014?) You can easily update your HPTuners if you have the license info.

[03Sierraslt]

So your running a 3bar sensor on the 2bar OS?

[mightyquickz28]

That seems strange. After seeing you pose that question, I went back and read that part of the OP notes. I'm definitely running a 3bar OS with a 3 bar MAP sensor.
Dave Wilson
'96 Z28 5.3 PRC stage 2.5 heads, ARP studs everywhere, Compstar H-Beam rods, Wiseco Forged pistons, ISKY Triple 12 cam, CXRacing tubular header hotside, PT7675 Turbo, 3" FMIC, 4300 stall Vigilante, Transbrake TH350, 3.08 gears, 315x35x17 M/T DR.
Best ET, blowing thru the converter 11.3 @ 120mph

[Nick@Newtech]

The MAP data you have for slope and offset are correct for the sensor. You should see around 100-105 KPA at atmosphere, so key on engine off, sometimes when datalogging that it does read zero for some reason, crank the engine a few turns not starting it and the scanner should show what the KPA is, like others have said make sure your wiring is correct, as you had to change the sensor plug most likely. Provided you get that sorted out its time to tune your VE, that is the proper way and not the band aid of skewing map offset like you have been doing. Obviously you should have a wide band in car. post up a log and tune so the forum can help you better. Good luck.