MAP sensor cleaning

Car stuff Oct 2, 2020

Ever since I got the car, it would stutter and hesitate during acceleration.  
A throttle body cleanup and new spark plugs made a lot of difference, but did not fix it completely. So there was something else still a bit off. My suspected offender was the a sensor in the intake manifold, a combined Manifold Absolute Pressure (MAP) and Mass Air Flow (MAF).  
This sensor measures the amount of pressure and airflow in the intake manifold - in other words, how much air the engine gets.  
Because the Engine Control Unit (ECU) uses both values to calculate what mixture the engine needs to run properly, it's important to have this specific sensor in good working order. That means it should be clean and accurate.  
But the sensor was very unlikely to be clean, due the state of the throttle body (soon™ to be seen in MOT 2020 - Part 4).  

Enough with the blabbering. Time for some pictures.

MAP sensor location, on the left side of the intake manifold. Below the air filter.
MAP sensor location, on the left side of the intake manifold. Below the air filter.
MAP sensor, next to the black part of the oil dipstick.
MAP sensor, next to the black part of the oil dipstick.

It's not really obvious on the second photo, but the MAP/MAF sensor is not secured with two screws like it should be. The electrical connector is also attached to the oil dipstick with a cable tie - this also shouldn't be the case. The "click" doesn't work anymore, so I guess this is a good alternative.

A better view of the MAP/MAF sensor with missing screws.
A better view of the MAP/MAF sensor with missing screws,

But the plastic notch on one side with a cable tie on the other provided enough grip. The sensor has been there since at least 30.000 kilometres without a problem. So it probably can go back in there like that without a problem.

The sensor, as seen from the side.
The sensor, as seen from the side.
The sensor, full of coal and soot from the EGR system.
The sensor, full of coal and soot from the EGR system.

Now the actual cleaning. Due to the sensitivity of the electronics, you can't just grab out a fine scrubber and some brake cleaner. Doing so will almost certainly ruin the sensor. The only thing possible without risking breaking it, was to apply electronics cleaner. In specific "Air Flow Sensor Cleaner".
Apply a bit, let it do it's job, apply a bit etc. until you're happy with the results.  

The air flow sensor cleaner did a pretty good job.
The cleaned sensor, still rather dirty
The cleaned sensor, still rather dirty

After a bit of scrubbing, there was still grime that wouldn't come off. It seemed to not make sense wasting anymore of the cleaner, it was not cheap and I could use it again in the future.  So I put the sensor back.
That was not easy at all. I don't know what I did to get it out there that easy, but it sure wouldn't go back in on it's own.
The retainers (marked on the picture) made it very hard to navigate around the oil dipstick into the guides.

Sensor back in place, held in by the o-ring. Cut cable tie visible.
Sensor back in place, held in by the o-ring. Cut cable tie visible.

After some fiddling and forceful persuading, I could convince the sensor to hop in to place.  
Another cable tie and the physical part was done.  

Check engine light illuminated
Check engine light illuminated

The ECU wasn't very happy with my DIY-ing, and turned on the check engine light.  Excepted results were airflow sensor problems, since it was disconnected while the ECU still had power.  
And just as suspected, two air sensor related faults:  

Air intake temperature and pressure fault stored in the ECU.
Air intake temperature and pressure fault stored in the ECU.

After a quick wipe with the handy dandy OBD-2 reader, the ECU was happy again.
This has been the case for ~200km since, and the stutter during accelleration is no more.  

So once again, success. 😎  

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