Clean your MAF sensor, reset your PCM and rejuvenate your engine! (Tdci - diesel - 1.8)

*Posting also here since someone may find it useful*

Hi guys,

I just wanted to share my recent findings with you.

I have a 2007 1.8 tdci focus with 182.000 miles. I replaced the dmf and clutch (LuK kit) 6k miles ago and motor mounts 12k miles ago. I blanked the EGR. I also replaced both front ball joints and rear lower control arms. I also use a lubricating diesel additive in each tank which noticeably improves the engine smoothness, sound and response (I primarily use it to protect the fuel pump and injectors).

The egr blank and fuel additive significantly improved the overall driving experience, but I still felt it was hard to make smooth shifts as if the engine - transmission - wheels were not properly working together. I previously reseted my PCM (disconnecting the battery for few hours) which made a very minor difference.

Recently I was watching a video about MAF sensor and their role in engine performance (measuring grams of air going into the intake per second which dictates the amount of fuel injected into the cylinders) and since I always want to improve my driving experience I thought I might as well try cleaning it.

How I did it:

1. MAF is located directly next to airbox on the intake.

2. remove the connecter, mine was quite stuck so I pulled up the red clip and had to wiggle it left and right quite some time for it to release.

3.In my case the MAF was secured by two security torx bolts for which I used a small screwdriver to break off the security bit in the middle and unscrew them.

4. Here is how my MAF sensor looked when I pulled it out - very dirty wires! Your may not look dirty but the cleaning is usually still very beneficial since even very tiny particles of dirt effect it negatively.

5. I cleaned it using Liqui Moly MAF cleaner. It is very important to use MAF cleaner since others can leave residue after drying which will negatively impact the sensor function so use MAF cleaner or just leave it alone. I used quite a bit of spray - probably 50 ml to clean my since it was so dirty. Use short full bursts of spray to clean it. Mine was really soaked after the cleaning so I left it to dry for 1 hour. Here is a video I found on youtube: 

Can of liqui moly MAF cleaner I used.

6. Before I started removing MAF I disconnected both of cars battery terminals and connected them a jump cable just so to get any electricity out of the circuit. You can als try turning the light switch in the car on to try to get the electricity out. I left it like that for 5+ hours and the engine was completely cold when I reconnected the battery and reinstalled the MAF sensor. Having the engine be completely cold may be important since the car relearns some parameters when reconnecting the battery and starting it for the first time and this parameters could be different between when engine is cold or hot.

So what did I notice?

Car revs up and down so much smoother, when you are driving and apply the throttle or lift you foot off the throttle it is so much less jerky than before. The shifts can be therefore so much smoother and satisfying. It truly transformed my car. I would say the improvement is as big as blanking the egr so definitely worth it. I will be cleaning my MAF sensor every oil change from now on. 

I must also point out that I monitored the MAF values during driving with forscan before and after cleaning and I didnt notice any significant difference in values before and after so I suspect that sensor was showing right values before just the responsiveness of the sensor was not right.

Potential next things to improve?

Cleaning the MAP (measures the air pressure after the turbo and is also responsible for amount of fuel injected) sensor which is connected via a tube just before the EGR valve and could be therefore also clogged up somewhat by the carbon-oil sludge from egr.

Here is how MAP looks on my car (photo found on internet):

Red circle show where the MAP is connected to the intake, this photo was taken when i was replacing the turbo hose, note how much sludge is built up very near the MAP hole.

Ofcourse cleaning the Intake manifold of all the sludge would probably make a massive difference but it is quite of complicated job and I really don't want to break off any sludge that could end up in the cylinder or turbo.

I will probably drive the car as is for few weeks and try cleaning the MAP then.

In conclusion:

Try cleaning you MAF you may improve your car a lot for cheap with minimal work.

Hope someone finds this useful.