Map sensor bad? Reading high at idle

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Jan 20, 2007 | 04:55 PM

bluehawk2

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From: Tupelo, MS

Map sensor bad? Reading high at idle

My friend has been helping me tune my car and we noticed a problem with the map sensor. The map sensor is saying that i am running 55-60 kpa at idle. Then when I drive down the road it drops to around 40-45. Is my map sensor going bad or is there some other explanation for this?

Thanks

Jan 20, 2007 | 09:05 PM

bluehawk2

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From: Tupelo, MS

hmmmmmmmmmmm stumped me too

Jan 20, 2007 | 10:11 PM

2xLS1

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From: Warr Acres, OK

Those are normal MAP values for those conditions.

Jan 20, 2007 | 10:55 PM

txhorns281

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From: Houston, TX

Quote:

Originally Posted by bluehawk2

Cam = reduced idle vaccuum = increased idle MAP

Jan 20, 2007 | 11:02 PM

bluehawk2

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From: Tupelo, MS

Thanks, that's one less problem for me to worry about.

Jan 20, 2007 | 11:18 PM

bluehawk2

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From: Tupelo, MS

So, when i get out on the road an increase vacuum the map sensor reads less. map an vacuum are inversly related?

Jan 20, 2007 | 11:26 PM

2xLS1

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From: Warr Acres, OK

Depends on the units you are reading MAP in.
High kPa = Low in Hg
Low kPa = High in Hg

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Jan 21, 2007 | 09:13 AM

ChrisS@sdpc

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This is one place were metric units are really nice. ~100kPa is atmospheric (standard) but your specific atmospheric condition is affected greatly by your elevation. 100kPa is sea level, but in Denver you may only see 85kPa.

If MAP reads
0 - 100kPa = vacuum
> 100kPa = boost

Or you can substitute in your kPa value for your specific atmospheric conditions above. No more 10inHg of vacuum here, 7psi there, etc.

Last edited by ChrisS@sdpc; Jan 21, 2007 at 09:48 AM.

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Jan 21, 2007 | 09:21 AM

jimmyblue

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From: East Central Florida

Cams depress vacuum / raise MAP especially at lower RPM,
at cruise you are up in RPM and the available overlap-time
that makes for vacuum loss (drawing from both intake and
exhaust, whichever is "cheaper" for pressure) is cut back.

Vacuum =(BARO-MAP) in PCM-world.