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2007 F250 5.4 Baro reading?

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11 Jan 2020 20:26 #36534 by MTROTR
2007 F250 5.4 Baro reading? was created by MTROTR
Hello. Been working on this truck for too long. Started with a massive vacuum leak 0n the intake manifold which I replaced then the CMCV actuator was bad. then the B1S1 o2 sensor. and finally have it running but barely. struggles to idle. STFTs are all over the place depending on RPM. They seem consistently lean at low RPM. I can't keep it running at idle but at 950 RPM its showing 12-14 g/sec MAF and a Baro indication of 86 KPa. I am not sure but that seems like almost twice the air I should have at Idle and the Baro reading would indicate I am parked on the moon. I know this truck doesn't have an actual Baro sensor. I don't know where the Baro is calculated from. My thought is its cutting back the gas because it thinks I am in the clouds. I don't want to just change the MAF because I am out of any other ideas, but I am basically stuck. Any help on this would be appreciated greatly.

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11 Jan 2020 20:38 #36535 by Cheryl
Replied by Cheryl on topic 2007 F250 5.4 Baro reading?
Try resetting the kam? Also I’m used to seeing how on my scanner for baro reading. You sure there isn’t another vacuum leak?

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11 Jan 2020 21:01 #36537 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
I'm going to smoke check it again tomorrow. The smoke was so bad initialy I could have missed a smaller leak. I've reset and relearned a couple of times. I'm going to try a run with MAF disconnected although I don't know what bypass logic is in this truck. won't hurt to try. Thanks for quick response.

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12 Jan 2020 08:44 #36542 by juergen.scholl
Replied by juergen.scholl on topic 2007 F250 5.4 Baro reading?
What is your actual height above sea level? The reported 86 kpa corresponds to some 5000 feet/1500 meeters above sl, roughly.

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.

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12 Jan 2020 14:06 - 13 Jan 2020 06:38 #36549 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
I am about 600 feet above sea level. My actual Barometric Pressure is 30.02"Hg. which is about 101.5 KPa if my math is right so my Baro reading of 86 equates to about 25.5 ' Hg. What should the MAF be at idle. I am assuming for a 5.4 it should be around 6 g/sec.
Last edit: 13 Jan 2020 06:38 by MTROTR.

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13 Jan 2020 17:44 - 13 Jan 2020 18:39 #36575 by scannerjohn
Replied by scannerjohn on topic 2007 F250 5.4 Baro reading?
On Ford the baro is calculated from the MAF. You're correct, the g/s should be around the engine liter at idle... 5.4-6g/s. Unplug, if it runs better, MAF is most likely bad. MAF has four wires. Two grounds one power one signal. Grounds should be less than .1mv. Power is battery voltage. Signal, I think is half g/s at idle.

That bad MAF will cause the erratic 02 readings and the bad idle. Check the voltage readings before replacing the MAF.


Last edit: 13 Jan 2020 18:39 by scannerjohn.

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13 Jan 2020 21:00 #36585 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
Okay I tried unplugging MAF and it definatly idled better. I'm really leaning toward a bad MAF. I have bateery voltage on the red wire then a couple of milivolts on the next 2 koeo. and 35 mv at idle. 3.6 volts on one. i have more than 4 wires checking mitchels for pin out but I think I am putting a MAF in tomorrow. can i check grounds with test light to bat. Pos?

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13 Jan 2020 21:30 #36586 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
pin 6 red wire bat. voltage
pin 5 BK/Wh .015 volts koeo .036 idle ground?
pin 4 Tn/Lb ,015 volts koeo fluctuating 0 to .9 volts at idle Maf signal return
pin 3 Lb/Rd 3.6 volts at idle Maf signal
pins 1 and 2 are intake air temp sensor signal and return?
not positive my t-pins were good but i think it is still pointing to a bad maf

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13 Jan 2020 23:39 #36597 by scannerjohn
Replied by scannerjohn on topic 2007 F250 5.4 Baro reading?
4,5 and 6 wire sensors work the same... 6 wire has 3 for the MAF, 1 ECM ground and 2 for the IAT.

your powers and grounds look ok... wiring is good. Points to MAF sensor.


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14 Jan 2020 18:43 #36614 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
New MAF in. A bit better but still not drivable. I have to have a vacuum leak somewhere or possibly injector issues I suppose. For some reason I can't see misfire data. I have no codes but it won't idle. Especially after backing off throttle. It seems smooth at any rpm above 1000. But my Baro seems in the ballpark now. MAF at fast idle is about 9g/sec. Better than. 13 or 14 . Smoke test again tomorrow I guess. Ughhh!

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14 Jan 2020 18:51 #36615 by scannerjohn
Replied by scannerjohn on topic 2007 F250 5.4 Baro reading?
what are your short term and long term fuel trims at idle and when increasing to 2500 RPM


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14 Jan 2020 19:37 #36616 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
I started it without clearing the memory so my LTFT was still in the 20's but Short terms were -7 to plus 9. i shut down cleared memory and LTFT went to zero but Short term started climbing immediately. i'll post some numbers tomorrow. I'm done with it for tonight

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15 Jan 2020 16:33 #36652 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
This morning I started it up cold and it went straight to a high idle of 920 to 1000 RPM. Fuel trims were B1 Short term 0 Long term 23. B2 short term 22 long term 9. MAF was at 14 g/s.
1500 RPM B1 STFT 8 LTFT 17 B2 STFT -3 LTFT 8.6 MAF 18 G/S
2500 RPM B1 STFT 17 LTFT 0 B2 STFT -15 LTFT 0
So both LTFTs at 0 at 2500 rpm and STFTs one bank lean and one rich. btw after I changed the MAF sensor baro is reading 96 KPa. close to what I expect.

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15 Jan 2020 16:55 #36653 by Cheryl
Replied by Cheryl on topic 2007 F250 5.4 Baro reading?
Sounds like you need to reset kam after the maf replacement and see what happens

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15 Jan 2020 17:49 #36654 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
I have cleared the memory several times. i relearned the electric throttle body. . It doesn't seem to want to run at low idle. it is not smooth at all until about 1000 RPM. on the KOER test it runs smoothly at higher RPM but dies when it backs down to idle. it starts cold and high idles without much problem.

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15 Jan 2020 18:34 #36656 by scannerjohn
Replied by scannerjohn on topic 2007 F250 5.4 Baro reading?
did you do the smoke test again?
LTFT correcting at high RPM suggest a vacuum leak. what are the voltage readings on B1S1 and B2S1 (do same RPM test)


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16 Jan 2020 16:43 #36672 by MTROTR
Replied by MTROTR on topic 2007 F250 5.4 Baro reading?
I smoke checked it again. the only place I am getting smoke is the air filter housing. of course that is pre MAF and I don't think it is a problem but i pulled the filter and there is a gap around the edge which i suppose could cause some weird turbulent flow to mess with the MAF reading. O2 sensor voltages are cycling and look okay to me but I am going to try to get a picture of the wave.

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