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Thread: Barometer reading off?

  1. #1
    Mitsu booster
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    Barometer reading off?

    Not sure if this is the right section to post in but I think the problem lies in the tune. Needing some help with my newly installed engine. The vehicle is an 89 Daytona 2.5L with a 50 trim t3/4. I've finally got this thing running after nine years of collecting parts. The problem I'm having is the engine is running full rich. The pulse width is 5ms, the o2 sensor is maxed out because of this and this is at idle. I can't even run the engine any more because I'm afraid of washing my new rings out. With the short time I did have the engine running I noticed all the sensors read normal except the Barometer reading, it's reading 19.7in hg which means I should be at the top of Mt Hood and I'm at 150ft above sea level which should read 29.5in hg. From my understanding the baro sensor is supposed to take a sample at KOEO and save that for reference and it's not supposed to change until it takes another sample. Coolant temp and air charge temp were reading the same at cold start up and changed accordingly as it warmed up. Some background on the engine is it's running a BB flashable smec with 4 switchable tunes. I have the same results on all four tunes. The map sensor is a GM 3 bar, I swapped out the map with another brand and got the same baro reading. The tunes are calibrated for a 3 bar map. I've tried to artificially change the baro reading buy applying psi and by applying vacuum and the reading doesn't change. The map itself reads 1.6v at KOEO which is normal from what I understand and the map reading itself reads correctly (calculates correctly with the incorrect baro reading) and changes with throttle. 5v reference and ground are good at the map. My question is after all that, is it possible the barometer calibration in the tune is incorrect even though the 3 bar map was checked off in the tune. All these tunes are the base tunes that came with the ecu as set up by BB. BTW I am a 25yr mechanic but am an idiot when it comes to flashing tunes (trying to learn) and computer jargon (ie tbl. bin. fil. stuff). I do have the usb cable to hook my lap top to the ecu but I haven't been able to get my computer to recognize the com port yet.

  2. #2
    Supporting Member II Turbo Mopar Contributor tryingbe's Avatar
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    Re: Barometer reading off?

    What size injectors are you using?

    Are you using a wideband? If so, make and model? Are you using a stock narrow band for the ECU?

    Were you using a OTC scanner to read the MAP sensor? If so ignore the inch of HG reading, it's gonna be off because the OTC scanner is calibrated to read the voltage and display the inch of hg for a 2 bar map, not a 3 bar map. List the MAP voltage instead.

    Are you willing to learn to do the calibration yourself?

    Who did the calibration, and are you able to post it?

    When the CTS below certain temperature, the engine is not even using the o2 sensor for feedback.

  3. #3
    Mitsu booster
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    Re: Barometer reading off?

    I am using a Snap on scanner. It has +40 injectors and the map reading itself I donít think is the issue as itís computing the value correctly (absolute+/-boost or vacuum). Itís just that the absolute pressure reading is wrong from the beginning. I have a wide band but itís not hooked up yet, running off the O2 right now. I donít remember the voltage of the map at idle off the top of my head but KOEO was 1.6v.

  4. #4
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    Barometer reading off?

    I am willing to learn to do the calibration myself, I have been reading everything I can find on it and I have downloaded the appropriate programs to do so. Rob from BB did the tune that is in there now, it was a mail order tune and I understand that itís not going to be perfect out of the box but I would expect it to run quite a bit less rich than it does. My combination of parts is a tried and true combination thatís well matched and been done before by others. Also Rob is pretty familiar with 89 2.5Ls. I understand that the O2 is disregarded until the car goes into closed loop but the car goes into closed loop pretty quickly and the fuel trims did not improve even at normal operating temp. Unfortunately at this time I havenít been able to communicate between my lap top and the ecu so I canít retrieve the tune yet. I wonít have another chance to try until Thursday unfortunately. If I can retrieve it I will post it.

  5. #5
    Supporting Member II Turbo Mopar Contributor tryingbe's Avatar
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    Re: Barometer reading off?

    1st thing to do is to put the wideband in.

    Narrow band o2 is useless in tuning car as 11 : 1 afr is the same as 13 : 1 aft to the narrow band sensor.

  6. #6
    Mitsu booster
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    Barometer reading off?

    When I put the wideband in I have to set the tune up for that correct? Iím assuming you want it set up so the ecu reads the wideband and not just hooked to a gauge.

  7. #7
    Supporting Member II Turbo Mopar Contributor tryingbe's Avatar
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    Re: Barometer reading off?

    Quote Originally Posted by moparmike70 View Post
    When I put the wideband in I have to set the tune up for that correct?
    Not necessary and it also depends on the make and model of your wideband.

    Wideband with gauge can work independently or you could wire it to the ECU, but not needed and sometimes not recommended as wideband sensor sometimes do not produce the fast rich/lean signal the ECU is looking for.

    Your Snap on scanner will only ever show you the in hg of the 2 bar map sensor as that is what is programmed in the scanner. It doesn't know your car have a 3 bar map sensor.


  8. #8
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    Barometer reading off?

    Ok, I will set up the AF sensor with the gauge first because I think my set up doesnít have the conversion to run it in place of the O2. I have an Autometer gauge set up and the AF runs straight to the gauge not like an Innovate set up. I get what youíre saying about the scan tool now, just figured the scan tool would read what the ecu puts out and not change it based on the vehicle ID. Guess I got some work to do, thanks for the help so far.

  9. #9
    Supporting Member II Turbo Mopar Contributor tryingbe's Avatar
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    Re: Barometer reading off?

    Quote Originally Posted by moparmike70 View Post
    just figured the scan tool would read what the ecu puts out and not change it based on the vehicle ID.
    All map sensor works in 0-5 voltage. My OTC allows the option for me to read the MAP voltage instead of in hg , then you just use the above map.

  10. #10
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    Barometer reading off?

    89 Daytona 2.5l
    Last edited by moparmike70; 02-01-2019 at 08:58 AM.

  11. #11
    Mitsu booster
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    Re: Barometer reading off?

    I was able to read the first tune and save it on my computer but I can't do anything with it because it saved it as a bin file. From what I've read you can't read the bin file unless you have the matching asm file? I would assume that BB has the asm files. I haven't finished hooking up the A/F sensor yet but it should be done by Wednesday night. I found out the A/F is a Bosch LSU 4.2 sensor. Can't do anything with the tune in the car at the moment because MPTune is not recognizing the com port again.

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