bad map sensor

lenoble22

Well-known member
Joined
Sep 21, 2010
Location
Oshkosh, WI
TDI
2006 Jetta TDI Package 2
Hey guys, hooked up my car to vag com and it shows that I have a bad map sensor, which I hope to god this is the issue cause I think i've done everything else to fix my low power issue. So I have a couple questions
1. Obviously the junk yards around here do'nt have any tdis laying around, I heard somewhere that you can swap in a gasser map sensor its basicly the same thing or even a slight upgrade. Can someone tell me if thats true or not.
and
2. Where the heck is the map sensor located in the car, I know what it looks like but can't find it.
Thanks in advace
 

snakeye

Veteran Member
Joined
Dec 13, 2009
Location
Montreal, Canada
TDI
2003 Jetta and Wagon, GLS 5sp
The MAP sensor is located on the top of the intercooler. You can see it if you peek down in front of the washer reservoir, it has two screws holding it in place. Not sure if it's the same on non-tdi cars, but I know that there are at least two different versions on the MK4 TDIs, since my 2003's MAP sensor is not the same as on my father's 2001 and my brother's 2000 TDI.
 

lenoble22

Well-known member
Joined
Sep 21, 2010
Location
Oshkosh, WI
TDI
2006 Jetta TDI Package 2
Anyone else on the gasser map sensors?? Does anyone know the part number for the stock 2000 jetta alh map sensor. I'm assuming its a 2.5 bar. Think i'll just find a used on on ebay. Thanks!
 

lenoble22

Well-known member
Joined
Sep 21, 2010
Location
Oshkosh, WI
TDI
2006 Jetta TDI Package 2
I bought a new sensor off the internet and put the new one in today and it didnt' help at all. The sensor that I pulled out was all full of oil. is that common?? Now its throwing code P1592 for the map sensor but it wasn't before i changed it. is there some kind of trick that i'm missing?/ any help apreciated.
 

phaser

Veteran Member
Joined
Apr 18, 2004
Location
Oregon
TDI
2004 Jetta PD - 490k
That was nearly seven years ago, and lenoble22 last posted on 09-26-13.

.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
And we could have guessed the MAP was not going to fix his problem, as they rarely ever fail.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Well, it was worth a shot...trying to cover all my bases as to why I have low power. Thanks guys.
Well, let's see if we can help anyway. Lots of things can cause low power, but start by answering a couple simple questions:

Are there any stored DTCs in the engine controller?

Did it start all of a sudden?
 

BakoTDI

Veteran Member
Joined
May 5, 2005
Location
Bakersfield, CA
TDI
Jetta, MK7
Are there any stored DTCs in the engine controller?

Did it start all of a sudden?
No codes
Have intermittent surges of power. I have pinpointed a vacuum leak on the pump (loose nipple), but have tapped on the nipple to tighten it. Also used some sealer to secure more. Gave me about 5'' vacuum back. Will be doing a smoke test on the system to pinpoint any other leaks.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
You can watch actual vs. requested values with a suitable scan tool, may not be far enough off yet to flag a DTC, and the MAF generally won't ever flag one no matter how bad it gets.
 

BakoTDI

Veteran Member
Joined
May 5, 2005
Location
Bakersfield, CA
TDI
Jetta, MK7
You can watch actual vs. requested values with a suitable scan tool, may not be far enough off yet to flag a DTC, and the MAF generally won't ever flag one no matter how bad it gets.
Ok, I understand.

I have rented the VCDS tool from fixmyvw and I have checked for codes...which gives me none. However, I am super new to using one. Any particular tests I should be doing that are fundamental for beginning to figure out my car? :confused:
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
There are labeled Measuring Blocks in VCDS, you can just scroll through them starting with 001 and everything will be labeled.

Look for ones pertaining to charge pressure control, and you can compare actual vs. requested (it is helpful to just graph them, there is a tab for that). VCDS is pretty easy to use.

You'll need to drive the car under some varying conditions, which is why it is helpful to use the graph, that way you can do a floorboarded 3rd gear pull from 1500 to 4000 RPM and keep your eyes on the road, then stop and review the graph.

Another one to look at is MAF actual vs. requested.

Sounds like you have a plan of attack for checking the vacuum system, smoke machine works good, but you also need to check the one-way valve (I call these the "ying yang" valve, as it is white and black).

The vacuum system looks daunting, but it is actually pretty simple, and the whole thing can be removed in one nice neat chunk from the car with two nuts and a couple electrical connectors.

I rebuild ALH vacuum harnesses all the time, as well as replace cracked booster tubes. Sometimes, at this point given the age of ALL the ALH cars, it is just not worth trying to find some tiny little issue with the vacuum system, I just pull the whole thing out, rebuild it on the bench, check the valve and the VNT actuator, as well as the reservoir ball on the front of the engine, and put it all back together. At least then, regardless, you KNOW that part is good and you won't be chasing anything with it for years to come.
 

BakoTDI

Veteran Member
Joined
May 5, 2005
Location
Bakersfield, CA
TDI
Jetta, MK7
Plumb the gauge directly onto the n75 line that goes to turbo. If you don't see 25 in Hg or more vac max, you might have a leaky n75 or a leaky vac pump. Check the vac pump by hooking the gauge to the main vac line that comes off of it. Should be more than 25 in Hg, ideally 30.
Great info, thank you for your awesome input! I'm screenshooting this post!
Regarding the reservoir, I read that I can check vacuum pressure at the end of the hose going to it and it should be around 25'', and that the vacuum on the hose going to turbo actuator should be about the same...I just checked that and I only get about 10''...should I be worried then that my N75 could be the culprit? I checked vacuum right after the vacuum pump nipple (infamous loose nipple) and I get about 20".
 
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Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
Oilhammer is right, they seldom fail but they will fail... A few years ago the market was flooded with bad knockoffs that did not work. The one you have now should have a split in the ring insert where the screws go through, if there is no split is is a bad part. I know as I purchased one myself. I would be very wary about purchasing a MAP sensor off of eBay. Just my $0.02
 
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