MAP sensor what does it actually do?

[1fast97gsx]

manifold air pressure sensor ... what does it actually do? I know it reads the pressure, but what does it do with these values?

 

[kpt4321]

On a 2g DSM with a 4G63, which is a motor run by a mass airflow air metering system, the MDP sensor (not MAP) is there to make sure the emissions equipment (particularily the EGR) is working correctly.

 

[1fast97gsx]

Does the MDP sensor affect idle?

I'm having problems with getting the car to idle below 1500 rpm on my new motor. I did a 1g head swap on a 2g block so I had to drill a hole for the sensor in the 1g intake manifold. Well instead of welding the plate and drilling a hole in that, I did it the ghetto way and just drilled a hole directly into the manifold, and then 2 more little holes and I put bolts with locking washers and nuts through the 2 little holes and the sensor is in the big hole. I also used RTV to help seal.

Seems ok and doesn't seem to leak out of there but I'm just wondering because I can't figure out what else would cause my idle problem...

 

[dreamdemon]

Is the throttle cable too tight? Did you screw in the throttle stop switch too far? Did you adjust the BISS with the timing grounded? Is the BISS o-ring leaking?

*This is 98TsiAWD*

 

[1fast97gsx]

Is the throttle cable too tight? Did you screw in the throttle stop switch too far? Did you adjust the BISS with the timing grounded? Is the BISS o-ring leaking?

*This is 98TsiAWD*

98tsiawd-

Throttle cable is adjusted right I'm sure, the stop switch should be fine as well. Nothing is leaking, but I didn't really mess with the BISS screw. The thing is last year it ran fine on this exact throttle body and nothing was altered on it except for the 2 coolant lines going to them ... I blocked that off and looped them but I'm going to undo that today because people said that could be a big part of the problem. Thanks.

PS. I did a boost leak test and found 1 major leak ... thought that would help but it didn't. The weird thing is if I hook up the leak tester and start pumping in air I can hear it where the intake manifold meets the head ... like it doesn't sound like it's leaking at all ... it sounds more like it's hissing into the head ... however I always though that if you do a boost leak test you can pump it up to about 20 psi or so and the system will stay pressurized? I can pump it up and I hear no leaks or anything ( just the really deep hissing of air going from the intake manifold into the head ) but as soon as I stop pumping air my boost gauge slowly drops. Is that normal?

 

[Corman12345]

On a 2g DSM with a 4G63, which is a motor run by a mass airflow air metering system, the MAP sensor is there to make sure the emissions equipment (particularily the EGR) is working correctly.

What if you have your EGR blocked off??

 

[1fast97gsx]

What if you have your EGR blocked off??

Yea I'm wondering about this now too ... can I just block off the egr and elliminate the sensor completely?

 

[98TsiAWD]

Yea I'm wondering about this now too ... can I just block off the egr and elliminate the sensor completely?

Yes you can, if you need the blockoff plate, I have one laying around on a 1g intake manny.

As far as the air leaking into the head during your boost leak test. That is completely normal. With the cams installed, there is never a moment when Every single vavle is closed. This is why air is getting into the comb. chamber and back out the exhaust.

Adjust that BISS by the manual and you "should" be good to go. You were running a 2g intake manny 7 months ago or not? If so I think the flow characteristics of the manifold might throw off the Biss, and this is why it would need readjusting.

 

[1fast97gsx]

Yes you can, if you need the blockoff plate, I have one laying around on a 1g intake manny.

As far as the air leaking into the head during your boost leak test. That is completely normal. With the cams installed, there is never a moment when Every single vavle is closed. This is why air is getting into the comb. chamber and back out the exhaust.

Adjust that BISS by the manual and you "should" be good to go. You were running a 2g intake manny 7 months ago or not? If so I think the flow characteristics of the manifold might throw off the Biss, and this is why it would need readjusting.

Yea I was running a 2g intake manifold before the winter. I adjusted the biss screw and reconnected the coolant lines to the throttle body and it runs awesome now. Ok that's cool about the leak tester then. I did a compression test today and it came out pretty decent. It was like 168, 163, 163, 167 .. I was hoping it'd be more consistant but it's ok. ( 8.5:1 ross pistons with metal headgasket ) How much for the block off plate? I'll take that for sure. You take paypal? Thanks for the help.