my MAP (intake manifold absolute pressure) is low

[turboLude]

Connected a Scan-Tool to my OBD2 system and found out that my intake manifold absolute pressure is low at idle, reading at 36 kPA +/- 2.
I need to be above 75 kPA at idle in order to run a OBD diagnostic testing for code P0420 (catalyst system efficiency below threshold). I have met aLl other conditions for running the diagnostic.

What are some of the reasons why my MAP sensor would should low pressure?

[Skeith]

What have you tried? Have you directly ported a vacuum guage to check the pressure? Pull your vac line off the brake booser and use that to port
your vacuum guage. Not sure what kPA should read, but you should be in the range of 16-18 inHg. (IIRC)
If that checks out, check the quality of the ground on your MAP. Make sure the vac line to the MAP isnt obstructed.
Maybe go to the wreaker and snag a used MAP for $5 and see if it changes the reading.

[caffeine]

36 kPa at idle sounds totally normal... I'd be worried if it were 76.

[turboLude]

36 kPa at idle sounds totally normal... I'd be worried if it were 76.

that is approx 10.3 inHg, you are saying that is normal at idle?

according to the service manual, in order to run and diagnose/test the catalyst and code p0420, I need to be above 75 kPA (or 22.15 inHg) pressure ..
this information can also be found at .. http://www.hotrodlane.cc/New%20LS%20...TC%20P0420.htm and .. http://www.bonnevillepro.com/forums/...hp?f=1&t=14564 .. the cars may not be the same, but the testing procedure does not change.

Can someone please verify

[robertisaar]

i think that is being referenced in vacuum, not MAP. 100kPa MAP is 1 atmosphere of pressure. 36kPa MAP is a good amount of vacuum for idle. 75 at idle is quite high.

what year/make/model/engine are you dealing with? i have the chart open for a 97 monte 3.4 with P0420 and i'm not seeing MAP being referenced at all(unless it is considered "load", in which case, needs to be 63% or less). this test is done between 20 and 75MPH as well.

[turboLude]

i think that is being referenced in vacuum, not MAP. 100kPa MAP is 1 atmosphere of pressure. 36kPa MAP is a good amount of vacuum for idle. 75 at idle is quite high.

what year/make/model/engine are you dealing with? i have the chart open for a 97 monte 3.4 with P0420 and i'm not seeing MAP being referenced at all(unless it is considered "load", in which case, needs to be 63% or less). this test is done between 20 and 75MPH as well.

yeah could be.
This is a 2001 Pontiac Grand Prix, 3.1L v6
The reference for barometric pressure on the chart relates to outside environment or pressure within the manifold ?

[robertisaar]

barometric is measure of air pressure external to the engine. i can see where you have the confusion, since the MAP sensor is used to read baro pressure immediately before cranking and at certain RPM ranges when WOT.

[turboLude]

haha, totally misread/confused that part of the chart, thanks
I guess my MAP sensor is okay then,
just trying to figure out why my car would not go into diagnostic mode for the catalyst, something is not working right, have to look into this further

[js35]

I dread the day when emissions comes to my state, anyhow, check your fuel trims with a scanner, it wont even begin if the fuel trims are out to lunch or you are flaging misfires, or maybe you need to take a longer trip with the vehicle. Here's some handy info: http://www.easterncatalytic.com/educ...he-po42o-code/