So long story short, have been running a maf tune but finally got a 2 bar map. issue is i got it to run fine past 1200 rpm but anything less it seems the kpa goes berserk and kills the truck. just wondering if maybe i missed something and could anyone just throw some advise.
73# uncapped injectors
BTR stage 2 weekend warrior cam
.600 lift springs
Gt45 turbo in truck bed
Last edited by Moistbread; 07-16-2022 at 08:10 PM.
Shouldn't any MAP sensor read normal atmospheric pressure of ~100kPa at key on engine off, no matter if it's 1/2/3/50-bar? Why is yours showing 195?
That’s exactly my concern. I bought it directly from advanced auto so I’d imagine it isn’t defective but can’t rule that out unless I have a issue in my tune.Originally Posted by blindsquirrel
Aftermarket parts are junk anymore these days. I cant count how many times I've wasted time on aftermarket sensors and hardware, just to end up installing new OEM parts. It's best to just use OEM parts, especially when it comes to sensors IMO.
Confused on when i said it was "aftermarket"? its a ACDelco from a 2005 cobalt SS...
Cobalt MAP sensor, or Cobalt BARO sensor being used as a MAP sensor?
And it's pinned correctly? A=loref, B=signal, C=5vref?
screenshot.17-07-2022 15.41.12.png
Have you done a bypass test while watching the scanner readings? Unplug sensor, scanner MAP should show... whatever minimum value, very low kPa. Jumper the 5vref over to signal and it should read max kPa. If those test normal I'd then go back to the previous MAP sensor & the matching linear/offset in the tune file and prove that the PCM is capable of giving valid readings from a known-good setup. After that the only thing left is a goofy sensor.
Cobalt Baro sensor. heres a log of me just turning maf back to primary with the same tune. map is reading 100kpa at idle. iv'e read numerous times of people using this baro sensor as a ls map. confused on what could be throwing it. also using the 2 bar map OS.
Does not answer if it reads low when unplugged and high when jumpered to 5v. I think you already know that 100kPa at idle is way wrong. Do the tests above and it will pin down whether it's a tune/PCM issue or a sensor issue. Gotta know which one is at fault in order to fix it.
Really appreciate the help man,
So disconnecting I’m at 50-55kpa. Jumped im at max 207.
Should be much less than 50kPa with the sensor unplugged. Verify that by jumping ground to the signal wire, see if you can force it lower than that.
Also, might be interesting to see if there's a difference in using the loref ground at the sensor pigtail to ground the sensor wire, and using battery or chassis ground to ground it. This sounds like a harness issue, kinda.
Out of curiosity, is there any voltage on the signal wire with the sensor unplugged? An open circuit reading of 50kPa would indicate that's a possibility. Signal wire should have 0.00 volts and a scanner reading of the absolute minimum it's able to read with the sensor unplugged.
So unplugged and grounded to chassis: still 54
No voltage coming from signal wire
Plugging in old 1 bar puts me at 90kpa idle now with the 2 bar OS.
Dropped the linear from 200 to 100 and offset 8.3 to 10.33: 1 bar and 2 bar is now at 40-50kpa idle.
And I have the manifold absolute pressure - 2 bar channel reading not the SAE.
Last edited by Moistbread; 07-17-2022 at 07:08 PM.
Interesting update. The “2 bar” map sensor is reading 4.8 volts out the signal. I thought all 2bars were 2.7 volt’s?
Alright, went to advanced and dealt with their nonsense of “that’s what the computer says”.. only had a “carquest” map that actually volted out to 2.4 volts. Now idling with 200 linear and 8.33 offset at 45kpa idle. So hopefully it was just a stupid mishap or map sensor’s.
Maybe 2.7 volts at atmospheric, that's right close to the middle of the range. They all go from not quite zero to just about 5 volts. The 1-bar will be nearly 5v at normal atmo while the 2-bar will be at only half scale.
yeah did a test run with the car quest that actually volts out at 2.7 and surprisingly besides the 115kpa+ afr ran outstanding. thanks again man. im hoping this maybe the end of this issue although it never did explain the 50 kpa disconnected lmfao.
This one definitely looks suspicious. For some reason GEN 3 2/3 bar OS's will not update the map sensor KOEO. This doesn't look like that though. Especially as he shuts it down.
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Yeah it’s definitely a weird one. I ended up going and swapping the sensor out for a aftermarket “CarQuest” sensor and it ran great last night. The last log “working” was with the new 2 bar.
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