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Title: Map pressure at idle Post by: turbo944s2 on October 11, 2016, 12:19:51 PM I vagcomed my car today and I got a map sensor reading of 990mbar at idle. I checked the sensor, the o-ring, check for vacuum leaks, my boost gauge is reading -20 in hg. Any suggestions of what could be wrong ?
Sent from my 831C using Tapatalk Title: Re: Map pressure at idle Post by: nyet on October 11, 2016, 12:21:49 PM I vagcomed my car today and I got a map sensor reading of 990mbar at idle. I checked the sensor, the o-ring, check for vacuum leaks, my boost gauge is reading -20 in hg. Any suggestions of what could be wrong ? MAP is a misnomer. The stock pressure sensor location is upstream of the throttle body. Your boost gauge is likely downstream. Title: Re: Post by: turbo944s2 on October 11, 2016, 12:53:17 PM Thanks for the response. I put a new map sensor in and it is still reading 990mbar. 990mbar is almost atmospheric pressure, so I must have a huge leak somewhere ?
Sent from my 831C using Tapatalk Title: Re: Post by: nyet on October 11, 2016, 12:58:48 PM Thanks for the response. I put a new map sensor in and it is still reading 990mbar. 990mbar is almost atmospheric pressure, so I must have a huge leak somewhere ? So, did you read my post explaining that your "MAP" (a MISNOMER) sensor is *upstream* of the throttle body? Any idea what that means? Title: Re: Post by: turbo944s2 on October 11, 2016, 01:05:20 PM When you said misnomer , I thought that you meant the map sensor was broken. Up stream means it is before the throttle body. So you're saying inspect everything before the throttle body?
Sent from my 831C using Tapatalk Title: Re: Post by: nyet on October 11, 2016, 01:08:25 PM When you said misnomer , I thought that you meant the map sensor was broken. misnomer n 1: an incorrect or unsuitable name MAP stands for "Manifold Absolute Pressure". Is the manifold upstream or downstream of the throttle body? Quote Up stream means it is before the throttle body. So you're saying inspect everything before the throttle body? No. At idle, is the throttle plate closed or open? When fully open, the pressure differential between upstream and downstream of the throttle plate is near zero. When closed, what is the pressure differential? Title: Re: Map pressure at idle Post by: turbo944s2 on October 11, 2016, 01:19:58 PM The throttle plate at Idle is almost fully closed. When closed the differential pressure should be high because one side is under a vacuum and the other side is exposed to atmosphere?
Title: Re: Map pressure at idle Post by: nyet on October 11, 2016, 01:21:26 PM Almost there :)
Title: Re: Map pressure at idle Post by: SB_GLI on October 11, 2016, 01:27:52 PM What he is trying to say is that the reading is accurate. He is just trying to explain to you why it is accurate. The MAP is upstream of the throttle plate. When the plate is closed, there is no charge (or vacuum) in the charge pipes, thus the readings near atmospheric pressure.
Title: Re: Post by: turbo944s2 on October 11, 2016, 01:35:14 PM Hmm is the sensor reading in absolute pressure? If it is then it's reading correctly.
Sent from my 831C using Tapatalk Title: Re: Post by: turbo944s2 on October 11, 2016, 01:36:30 PM Thanks guys. I'm getting a boost pressure deviation dtc. I'm trying to figure out why. There is a 600bar difference between the sensor and the requested. If I raise the requested up higher that should go away. I didn't want to do that blindly without some insite.
Sent from my 831C using Tapatalk Title: Re: Post by: nyet on October 11, 2016, 01:43:24 PM Thanks guys. I'm getting a boost pressure deviation dtc. I'm trying to figure out why. There is a 600bar difference between the sensor and the requested. Post the DTC. I doubt it is related to idle.Quote If I raise the requested up higher that should go away. I didn't want to do that blindly without some insite. Yes, do not raise requested higher blindly until you diagnose precisely what is going on. Post logs, preferably 3rd gear WOT. Depending on the DTC, you should not be throwing it part throttle or idle. Do not post VCDS logs. Get ME7Logger running, or take the car to a qualified mechanic. Title: Re: Post by: SB_GLI on October 12, 2016, 07:15:57 AM Thanks guys. I'm getting a boost pressure deviation dtc. I'm trying to figure out why. There is a 600bar difference between the sensor and the requested. MAP reading is likely correct. You could/should verify with a manual gauge. You likely have a boost leak somewhere causing underboost. Title: Re: Post by: turbo944s2 on October 12, 2016, 05:40:44 PM 000665 - Boost Pressure Regulation P0299 - 002 - Control Range Not Reached - Intermittent Freeze Frame: Fault Status: 00100010 Fault Priority: 2 Fault Frequency: 2 Reset counter: 255 Mileage: 115516 km Time Indication: 0 Freeze Frame: RPM: 3286 /min Load: 21.2 % Speed: 75.0 km/h Temperature: 90.0°C Temperature: 33.0°C Absolute Pres.: 980.0 mbar Voltage: 13.716 V I pressurized the entire system to 20 psi last week and fixed all of the boost leaks I had. I will start working on ME7 logger asap. |