After replacing ignition coil and plug for #3 cylinder, my mechanic found heavy carbon buildup on all valves. The car only has 108K miles. He is replacing the fuel injector and egr valve along with cleaning the valves.
He plans on cleaning using WD40 and a brush.
Is this a common problem?
Thanks.
On 17/6/21 11:38 am, AK wrote:
After replacing ignition coil and plug for #3 cylinder, my mechanic found heavy carbon buildup on all valves. The car only has 108K miles. He is replacing the fuel injector and egr valve along with cleaning the valves.The engine in those is a Gasoline Direct Injection (GDI) and they have a habit of coating the intake tract and the *backs* of the *inlet valves*
with carbon. That is because the engine *injects* fuel directly into the cylinder so the intake tract and backs of inlet valves never gets fuel
wash as they would were the engine carbureted or port injected.
What happens is the PCV and EGR system contribute to an oil film in the intake system and this unburnt oil and fuel turns into carbon on the
backs of the hot inlet valves. It can build up sufficiently to restrict
air flow into the engine - which is what I presume your engine is doing.
He plans on cleaning using WD40 and a brush.Won't work. The carbon gets baked on rock hard and is damnably difficult
to shift. Look up *seafoam* which can be used to clean the carbon on the backs of the valves. Note, if seafoam is added to the fuel tank, it will *not* prevent the backs of the intake valves from carbon build up since
the fuel is injected directly into the cylinders. It will only be able
to clean the combustion chambers and valve faces.
Is this a common problem?Yes, very common.
Thanks.
Look up carbon build up on the backs of intake valves. You will likely
find plenty of info and even video clips on the issue.
--
Xeno
Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)
On Thursday, June 17, 2021 at 7:09:47 AM UTC-5, Xeno wrote:
On 17/6/21 11:38 am, AK wrote:
After replacing ignition coil and plug for #3 cylinder, my mechanic found heavy carbon buildup on all valves. The car only has 108K miles. He is replacing the fuel injector and egr valve along with cleaning the valves.The engine in those is a Gasoline Direct Injection (GDI) and they have a
habit of coating the intake tract and the *backs* of the *inlet valves*
with carbon. That is because the engine *injects* fuel directly into the
cylinder so the intake tract and backs of inlet valves never gets fuel
wash as they would were the engine carbureted or port injected.
What happens is the PCV and EGR system contribute to an oil film in the
intake system and this unburnt oil and fuel turns into carbon on the
backs of the hot inlet valves. It can build up sufficiently to restrict
air flow into the engine - which is what I presume your engine is doing.
He plans on cleaning using WD40 and a brush.Won't work. The carbon gets baked on rock hard and is damnably difficult
to shift. Look up *seafoam* which can be used to clean the carbon on the
backs of the valves. Note, if seafoam is added to the fuel tank, it will
*not* prevent the backs of the intake valves from carbon build up since
the fuel is injected directly into the cylinders. It will only be able
to clean the combustion chambers and valve faces.
Is this a common problem?Yes, very common.
Thanks.Look up carbon build up on the backs of intake valves. You will likely
find plenty of info and even video clips on the issue.
--
Xeno
Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)
Actually my mechanic was able to remove most of the carbon.
I will have this done every 50K so it never gets real bad.
Shame on Mazda for using direct fuel injection. :-)
Andy
On Thursday, June 17, 2021 at 7:09:47 AM UTC-5, Xeno wrote:
On 17/6/21 11:38 am, AK wrote:
After replacing ignition coil and plug for #3 cylinder, my mechanic found heavy carbon buildup on all valves. The car only has 108K miles. He is replacing the fuel injector and egr valve along with cleaning the valves.The engine in those is a Gasoline Direct Injection (GDI) and they have a
habit of coating the intake tract and the *backs* of the *inlet valves*
with carbon. That is because the engine *injects* fuel directly into the
cylinder so the intake tract and backs of inlet valves never gets fuel
wash as they would were the engine carbureted or port injected.
What happens is the PCV and EGR system contribute to an oil film in the
intake system and this unburnt oil and fuel turns into carbon on the
backs of the hot inlet valves. It can build up sufficiently to restrict
air flow into the engine - which is what I presume your engine is doing.
He plans on cleaning using WD40 and a brush.Won't work. The carbon gets baked on rock hard and is damnably difficult
to shift. Look up *seafoam* which can be used to clean the carbon on the
backs of the valves. Note, if seafoam is added to the fuel tank, it will
*not* prevent the backs of the intake valves from carbon build up since
the fuel is injected directly into the cylinders. It will only be able
to clean the combustion chambers and valve faces.
Is this a common problem?Yes, very common.
Look up carbon build up on the backs of intake valves. You will likely
Thanks.
find plenty of info and even video clips on the issue.
--
Xeno
Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)
Actually my mechanic was able to remove most of the carbon.
I will have this done every 50K so it never gets real bad.
Shame on Mazda for using direct fuel injection. :-)
All in the name of *efficiency*, in particular fuel efficiency, and
Mazda are not alone. They can run in stratified charge mode at very lean >mixtures in cruise - up to 40:1 in some instances. The problem is - they >introduce a whole new raft of problems.
Wait until you see HCCI/CAI rolled out - that will be interesting.
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