Negative Boost

[rman]

During a 1400 mile trip, sometime halfway, I noticed at idle and slow/parking lot speeds i was seeing about -2 psi.

Now, I'm seeing the lowest of about -1
Boost builds fine otherwise.

KOEO i see about -0.40

Is this a clogged MAP fitting? Or failing MAP sensor?

2003 6.0

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[kwelch08]

Did you go up in elevation?

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[6.0 Tech]

:whs: most electronic gauges use a specific pressure, most likely 14.7 as thats what sea level psi is, as its base for boost readings. For some reason they do not use the factory map or mgp readings in the pcm, which will alter based on baro pressure. Every once in a while we will see -.04--.1 at idle thru the ids, but not typically.

 

[rman]

Did you go up in elevation?

Sent from my HTC One M9 using Tapatalk

i have no idea haha. San Diego to Fort Worth

:whs: most electronic gauges use a specific pressure, most likely 14.7 as thats what sea level psi is, as its base for boost readings. For some reason they do not use the factory map or mgp readings in the pcm, which will alter based on baro pressure. Every once in a while we will see -.04--.1 at idle thru the ids, but not typically.

Forgot to mention, it's a Livewire TS.

I was under the impression that the PCM/OBD based boost gauges read off MAP?

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[rman]

Did you go up in elevation?

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ok it looks like i went from about 420' to 650', so not a whole lot

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[kwelch08]

Hmm when I went to new Mexico I saw the same numbers as you are seeing but once I came back to the coast I saw .7-1psi at idle.

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[6.0 Tech]

i have no idea haha. San Diego to Fort Worth

Forgot to mention, it's a Livewire TS.

I was under the impression that the PCM/OBD based boost gauges read off MAP?

Sent from my Nokia 5160 using Snake

I would tend to agree, except after driving my buddies truck with an x4 for gauges. The idle boost goes all over yhe place with elevation, where a typical ids reading wouldnt.