OLD NAVY: Tech Discussion of MAP Sensor/Boost Pressure Senso

DarbyWalters · **Posted:** Wed Jul 18, 2007 6:06 pm

The ECM/PCM depends on the data coming from this dual sensor (AKA MAP Sensor but refered to as Boost Pressure Sensor in FSM) - both intake air temperature and air pressure are measured with this sensor. The ECM/PCM in turn uses this information to calculate how much fuel to inject into the cylinders - so this sensor has a direct relationship to the power, efficiency, fuel economy and soot output of the engine. The egr design is going to be an ongoing maintenance issue with this and any other egr equipped diesel. This soot will cause degraded sensor performance problems due to carbon buildup in the intake system and anything in its path negatively affected by soot and carbon buildup. It will also affect ring wear and engine longevity. I use chlorine free disk brake cleaner from the auto parts store to clean the sensor. That said I not sure if any cleaner we could buy at the parts store would harm the sensor seeing how "tuff" this thing has to be to work where it is located.

Ranger1's thinking is (I agree) with all that soot buildup, the ECM was using stored values, as temperature and boost couldn't possibly be measured correctly with that clogging. I'm deducing that on the temperature, the soot acted as an insulator, keeping the cold readings for too long on warmup, causing overfueling, and kept heat on the sensor once the engine was up to temperature, causing underfueling on longer trips.

This looks to be a 5000 mile/7500 kilometers cleaning job to have a proper running engine with current fuel. We can only hope ULSD may drastically change this for us.
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1. This is the sensor after removal, it requires a 4 mm allen wrench and I left the wiring attached in case I dropped the thing while removing. There is a tension washer under the screw and will require a magnet most likely to remove it from the manifold. Just lift the tab and pull the sensor off the warring harness. I didn't disconnect the battery before doing the cleaning, but I had no problem. However it might be wise to disconnect the cables to prevent any problems. One thing I did was remove the three holding nuts for the wiring harness to ease removal, but it is probably not necessary for most people.

2. This is where it pluggs into on the manifold.

3. This is a members sensor and it is solid crud.

4. This is the sensor from my CRD at 21,700 miles, and it was packed solid.

5. This is mine after cleaning.

gmctd · **Posted:** Tue Sep 25, 2007 4:57 pm

Just cleaned my son's recent acquisition, which was member Boxhead's CRD, at 53kmi - the cone-cage area above the green o-ring was just an amorphous blob, shapeless and undefined - I would suggest this be done immediately, and just as immediately install the ORM kit to prevent further incident - if the MAP sensor probe is like that, imagine what the inside of the intake plenum looks like, and the port runners, and intake valve area - clean it now, and get yer kit - ya snooze, ya lose

chrispitude · **Posted:** Sun Dec 02, 2007 6:36 pm

I cleaned my wife's MAP sensor today. Mine was also just a sooty blob at 42k miles:

Given how clogged this little MAP sensor was, I can't imagine what shape the rest of the intake is in.

Maybe it's time for a Provent.

On a side note - when I was removing the 4mm Allen bolt, I had a magnet ready to grab the tension washer that others have mentioned. However, there were no washers at all anywhere - it was just the MAP sensor itself and the 4mm bolt.

Did anyone else remove their MAP sensor and find that there were no washers? Where does the washer go - between the sensor and manifold, or the bolt head and the sensor? What purpose does it serve, and would it leak with the MAP sensor installed without the washer?

- Chris

gmctd · **Posted:** Mon Dec 03, 2007 11:47 am

Notice the aluminum insert in the module bolt-hole - that takes the main tension of the bolt torque, prevents distortion of the plastic housing as bolt is torqued - the washer is placed under the bolt-head to distribute lesser tension onto the plastic sensor housing, prevents cracking of the softer plastic - the threaded hole in the aluminum manifold is a blind hole, dead-ended, with no passage to the intake plenum - the sensor is sealed to the intake plenum by the green o-ring.

If ya got it, place the washer on the bolt B4 installation - no problem if missing, but if ya want one, MrMoparts should be able to fill the bill

chrispitude · **Posted:** Mon Dec 03, 2007 5:49 pm

Doh, I found it. It snuck by my magnet, and had rolled back to where the rear axle was!

Thanks a bunch gmctd,

- Chris

0311_DoC · **Posted:** Mon Dec 17, 2007 10:47 pm

So what do you clean this with? just soap and water or simple green ????

Endurance · **Posted:** Tue Dec 18, 2007 12:10 am

What I wanna see is a sensor after 20k miles of ORM.

gmctd · **Posted:** Tue Dec 18, 2007 1:09 am

Diesel fuel first, Doc, or Kerosene, or Varsol, or paint thinner (NOT lacquer thinner), then hot soapy water, heavy on the soap or Green, then a hot-water rinse if you don't have access to compressed air, so it will dry quickly

Yeah, me too, Endo - be interesting to see the result of our collective labor

0311_DoC · **Posted:** Thu Dec 20, 2007 3:42 pm

how do you get to the 4mm allen bolt? I cant seem to move my harness out of the way enuff to even get to it. i have removed the 3 lil retaining washers on top, but still not enuff play to get to the bolt

gmctd · **Posted:** Thu Dec 20, 2007 4:00 pm

Pull the plastic wiring harness tray up and off all three standoffs - takes a really good tug

0311_DoC · **Posted:** Thu Dec 20, 2007 4:16 pm

ok, I got it.. man mine doesn't look like the pic above... it looks wet and oily not dry????

0311_DoC · **Posted:** Thu Dec 20, 2007 4:22 pm

I know not the greatest pics but is this bad. since the ones above are dry?

gmctd · **Posted:** Thu Dec 20, 2007 7:12 pm

Bad, only in the sense that it is nasty wet - that's from the oily vapors from the CCV system - prolly time to clean the CCV puck and do the ORM\SEGR mod

0311_DoC · **Posted:** Thu Dec 20, 2007 9:35 pm

Ok how hard is it to clean the CCV puck, and where is that at etc....

gmctd · **Posted:** Thu Dec 20, 2007 10:26 pm

Here - http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=22703

0311_DoC · **Posted:** Thu Dec 20, 2007 10:28 pm

isnt that the elephant hose mod? so is that what I have to do, to clean the CCV puck thingy?

gmctd · **Posted:** Fri Dec 21, 2007 12:53 am

Yep, sorry - EHM, not ORM - the puck cover pops off via those four tabs in the four slots in the circumference - or just do the EHM, or better yet, the Provent\Racor similar

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

Cleaned mine today at 20k miles... I've run the ORM/SEGR for most of my vehicles life, and I almost always run B20 or B99, and stick to 5w40 oil (thinking 0w40 added to the problems with oil in the intake). I was hoping my MAP sensor would be in ok shape...

Well, kinda. It was not crusted into a blob like those shown in the photos. You could clearly see the plastic "cage", but the sensor inside the cage was caked in crud, and the whole assembly was wet with oil.

I used automotive electrical parts cleaner and a soft toothbrush to clean the crud off, let it dry, then re-assembled. No issues, though I did notice a very distinct drop in pitch in the sound of the engine's idle. Kind of hard to describe... not like the idle itself is faster or slower, but the engine noise seems a little deeper.

Anyway, I've been putting off the Provent/EHM mod, but it looks like I'm going to have to do it sooner rather than later. Also going to do it for the wife's TDI as well.

0311_DoC · **Posted:** Mon Jan 28, 2008 1:01 am

I finally got around to doing the EHM today. I just haven't taken off the the sensor yet to see what it looks like from last time

Doctor B · **Posted:** Thu Jun 05, 2008 11:40 pm

I am the proud new owner of a stock un-modded 06 CRD c 58k on it - and now I have modded.
EHM and ORM done this evening, and took out the MAP and cleaned it off with B12 Chemtool.
Nice and clean now, but it was a gooey blob of tar on there though - just like yours 0311_DoC.
I fear that's coating the intake manifold as well.
I'm hoping just running some Seafoam through it over time - with the mods in place -
will allow it to clean itself. The intake manifold job sounds rough.
This weekend the tapping of the stripped drain pan hole and placing of the Fumoto valve takes place.
What fun, what fun. Only a few more things to do and add, and I'll feel OK.

OLD NAVY: Tech Discussion of MAP Sensor/Boost Pressure Senso

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