Funny thing AFTER cleaning MAP sensor

danoid · **Posted:** Mon Aug 13, 2007 9:46 pm

First the usual. Yes I'm lazy, it took me 43,000 miles to clean my MAP sensor.

MASSIVE amounts of CRuD...

Cleaned it with brake cleaner...

But it's what happened AFTER that got my attention.

I was driving home today and tapped the overhead console to see how warm it was. 64°? Not likely. A couple of blocks later it read a more respectable 84°.

Here's what I think was happening... At each (cold) key up the MAP sensor and the ambient temp sensor shake hands and either agree or agree to disagree. If they disagree, one makes an adjustment until they agree again. Over the space of two+ years the offset learing amounted to around 20°. Then I changed the system and suddenly they disagree by 20° again.

The solution (I hope) is to Microsoft the car. Disconnect the battery for half an hour. I'll try that if it doesn't fix itself soon.

Anyone else have this happen to them?

DocB · **Posted:** Mon Aug 13, 2007 10:14 pm

Yea, my overhead thermometer's been a lot off in the last 3 weeks.
First, it reads some ridiculous #, then all of a sudden it shows something "more reasonable".
Haven't touched the MAP sensor yet though. (planning on it soon).
I'm just waiting a little longer to see what happens.
I just hate going back to the dealer.
BTW- I'm still waiting (1 1/2 months now) for a new blower motor to come in for the recall!

DZL_LOU · **Posted:** Mon Aug 13, 2007 11:28 pm

There is a good write up I did called MAP Sensor Operation in the FAQ's for the CRD. It is technically describing the operation of the MAP sensor.

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

Holy Shhhnikes! Looks like you stuck it in the mud.

CRDLIBERTY · **Joined:** Thu Aug 02, 2007 11:52 pm **Posts:** 72

I had a toyota tacoma 99 and installed a KandN at 100k i had a light come on everyone said its the maf well i checked and looked like newww! Yours is a problem lol thats way loaded up. Jeep should have to clean our rigs out

danoid · **Posted:** Tue Aug 14, 2007 11:55 am

It just dawned on me. If there's sensor offset learning on the manifold temperature, there are at least two other pressure sensors too (intake and engine controller). Definitely a reset required if they are offset learning also.

barnez224 · **Joined:** Fri Jan 19, 2007 11:28 am **Posts:** 130

Mine does this too but I don't think it is actually a problem. When I leave for work in the morning before it gets hot outside my thermometer will read the accurate temperature. I find when there is a big jump (like from 70 to 95 degrees, for example) after starting the Liberty up in the afternoon, it takes a few minutes for the thermometer to calibrate to the actual temperature. It seems to make the change quickly in the 5-10 degree range but anything more than that it needs more time to "think" about it.

BVCRD · **Posted:** Tue Aug 14, 2007 7:23 pm

You wasn't missing anything. Mine looked like that at 21,000 miles.

danoid · **Posted:** Tue Aug 14, 2007 8:37 pm

Still a 10°F temperature jump this afternoon. Microsofting (battery disconnect or 'reboot') tonight.

Cowpie1 · **Posted:** Tue Aug 14, 2007 10:04 pm

Wow... looks the EHM mod or a provent not used based on the look of that MAP sensor.

Mine just had carbon in a powdery form on the MAP.

danoid · **Posted:** Tue Aug 14, 2007 10:16 pm

Cowpie1 wrote:

Wow... looks the EHM mod or a provent not used based on the look of that MAP sensor.

Mine just had carbon in a powdery form on the MAP.

Yup. Just haven't figured out what to do with the provent drain. I'm trying to think of some way to return the drain into the sump.

Questions for provent users... Does it separate water? Is there water in the drainage? Is this off topic and I should start a new thread?

RTStabler51 · **Posted:** Tue Aug 14, 2007 10:16 pm

how the heck does the MAP sensor work that gunked up? I need to clean mine, I turn 36k tomorrow...

Timmaah! · **Posted:** Wed Aug 15, 2007 7:40 am

I had a toyota tacoma 99 and installed a KandN at 100k i had a light come on everyone said its the maf well i checked and looked like newww! Yours is a problem lol thats way loaded up. Jeep should have to clean our rigs out

The MAF sensor on my CRD looks like newww! too. How does your MAP sensor look?

Joe Romas · **Posted:** Wed Aug 15, 2007 7:52 am

danoid wrote:

Cowpie1 wrote:

Wow... looks the EHM mod or a provent not used based on the look of that MAP sensor.

Mine just had carbon in a powdery form on the MAP.

Yup. Just haven't figured out what to do with the provent drain. I'm trying to think of some way to return the drain into the sump.

Questions for provent users... Does it separate water? Is there water in the drainage? Is this off topic and I should start a new thread?

I have a plastic line on mine going to a small valve followed by another short piece of hose. I just open the valve and let it run into a bottle. What comes out is a sludge and the water is heavier and comes out first. It's all routed down next to the engine block. On bigger engines it just dumps into sump but I don't think I want this sludge back in my engine :roll:

BVCRD · **Posted:** Wed Aug 15, 2007 8:59 am

RTStabler51 wrote:

how the heck does the MAP sensor work that gunked up? I need to clean mine, I turn 36k tomorrow...

It doesn't or at least not very well. It may eventually get up to temp and try to work but it is severly hampered.

danoid · **Posted:** Wed Aug 15, 2007 11:52 am

An overnight battery disconnect cleared the sensor learned offsets. The overhead display read true to temperature on startup AND the engine was running real strong this morning.

Definitely something I'd recommend after cleaning up such a badly gunked sensor. 'Course you'll lose all your radio presets, clock, overhead fuel economy, etc...

BlackLibertyCRD · **Posted:** Wed Aug 15, 2007 9:02 pm

danoid wrote:

An overnight battery disconnect cleared the sensor learned offsets. The overhead display read true to temperature on startup AND the engine was running real strong this morning.

Definitely something I'd recommend after cleaning up such a badly gunked sensor. 'Course you'll lose all your radio presets, clock, overhead fuel economy, etc...

I did a one hour disconnect and didn't lose a thing. Must be a 2005 thing. I don't think overnight would make a differences.

danoid · **Posted:** Thu Aug 16, 2007 8:54 pm

Joe Romas wrote:

I have a plastic line on mine going to a small valve followed by another short piece of hose. I just open the valve and let it run into a bottle. What comes out is a sludge and the water is heavier and comes out first. It's all routed down next to the engine block. On bigger engines it just dumps into sump but I don't think I want this sludge back in my engine :roll:

If the Provent doesn't properly separate water out of the oil...Why should I spend $100 (or whatever)? Is there any benefit over a coke bottle filled with rags?

Joe Romas · **Posted:** Fri Aug 17, 2007 7:16 am

danoid wrote:

If the Provent doesn't properly separate water out of the oil...Why should I spend $100 (or whatever)? Is there any benefit over a coke bottle filled with rags?

The provent seperates the oil and water vapors from the intake air allowing the fumes to be cycled back into the intake without the oil :lol:

Dr. Diesel · **Joined:** Thu Aug 16, 2007 2:34 pm **Posts:** 4

The MAP/intake temp combined sensor will work even if plugged with soot particles. The gunk is actually the EGR gas combining with oil particles from the CCV system, it tends to build up over time. Worst case on a severely plugged sensor, the boost pressure may read slightly lower than normal and since the turbo is "closed-loop" on boost pressure the vanes may be in a more closed position in order to reach the set point pressure. Having more closed vanes increases the exhaust back-pressure and correspondingly degrades the fuel economy. If you unplug the MAF sensor, the EGR will turn off and the gunk will not build up anymore.

Funny thing AFTER cleaning MAP sensor

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