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DIY fix Code P0172

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orangehonda
2000rpm
2000rpm
Posts: 33
Joined: Fri Aug 22, 2014 1:13 am

DIY fix Code P0172

Post by orangehonda » Wed Feb 17, 2016 9:51 am

Wednesday, 17 February 2016
Car jerky...again?... Trouble shooting Code P0172
The last time this code P0172 came up, it was a result of EGR not seating & tighten properly.

http://eco-hondacar.blogspot.sg/2015/08 ... r-nut.html

What is P0172? http://www.obd-codes.com/p0172

Possible Symptoms
Irregular behavior
Possible Causes
Fuel system
Excessive fuel pressure
Leaking or contaminated fuel injectors
Leaking fuel pressure regulator
Low fuel pressure or running out of fuel
Vapor recovery system
Air leaks after the MAF
Vacuum leaks
Improper seated engine oil dipstick
Stuck EGR valve
Oil overfill
Cam timing
Cylinder compression
Exhaust leaks before or near HO2Ss.


My trouble shooting regime

Observation: The gear change was jerky from 1st to 2nd. Thereafter CEL appeared.

The OBD scanner reads: P0172 confirmed.


Transmission problem?
I thought it was the transmission since this vehicle had its transmission serviced before.

The transmission fluid was drained. Its color is clear red which was good.
There was some very very fine metal waste on the magnetic drain plug.
The fluid was passed through coffee filters and no deposits which is good.


Jerking persist after refill of transmission fluid

Finally caught the problem.
After investigation, it was a result of a leaky gasket on the valve cover.
That compromised the seal integrity resulting in vacuum leaks.

Now the engine computer calculates everything. The leak in vacuum threw the fuel calculation into disarray resulting in jerks.


The final fix

Most of you will not experience this, but for mine, the engine was lifted out of the body during the transmission service by a third party workshop. This is a service provided as "insurance" by a used car dealer. The valve train cover was found to be assembled but the seating is not aligned.

Image

The workshop personnel used silicon liquid gasket to patch this imperfection. Because of this misalignment, the rubber gasket on the valve cover cannot seal perfectly, resulting in vacuum leak.

Image

I finally zoomed on the oil spray which was usually absent in a well maintained compartment.
This is unusual because there should not be oil leaking out at all.

From here, i had to replace a new valve cover gasket and patch the imperfect seating with new silicon gasket.

Image

This rectification is simple. The trick is to wait out for the liquid silicon gasket to cure sufficiently.
For my case, i waited about 2 hours before usage of the vehicle.

A full cure would take about 1 day.

After this replacement, the P0172 went away.

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