Air Injection Solenoids and why you get a CEL
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Some cars I've seen with this issue have fairly low mileage, so normal wear is out.
I've also seen brand new heads that do not have this issue, so manufacturing defect is out.
None of these cars overheated or blew head gaskets.
That just leaves high exhaust gas temp. Since I've seen the issue on cars with widely varying setups, from different tuners including stock tune, OTS maps, and various custom tuners, I would rule out improper tuning as the cause. So what else would cause high EGT's on smog pump cars specifically?
-- Ed
I've also seen brand new heads that do not have this issue, so manufacturing defect is out.
None of these cars overheated or blew head gaskets.
That just leaves high exhaust gas temp. Since I've seen the issue on cars with widely varying setups, from different tuners including stock tune, OTS maps, and various custom tuners, I would rule out improper tuning as the cause. So what else would cause high EGT's on smog pump cars specifically?
-- Ed
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Take another look at these images, this is not from fresh air flowing through them under vacuum...if so, one would assume they would be pretty darn clean; not gummed up with carbon as well as broken down from heat which would be a result of back pressure on them, which is from the exhaust.
I guess we can all argue until we are blue in the face, to each's own on what you wish to believe...
-Noah
I guess we can all argue until we are blue in the face, to each's own on what you wish to believe...
-Noah
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Take another look at these images, this is not from fresh air flowing through them under vacuum...if so, one would assume they would be pretty darn clean; not gummed up with carbon as well as broken down from heat which would be a result of back pressure on them, which is from the exhaust.
I guess we can all argue until we are blue in the face, to each's own on what you wish to believe...
-Noah
I guess we can all argue until we are blue in the face, to each's own on what you wish to believe...
-Noah
Maybe I am wrong and something else is causing the valve guide wear, but I have not been able to identify it. The only commonality I've found so far is the smog pump. Maybe it's just from the normal operation of the pump? I just wouldn't think that it's on long enough to cause that kind of damage.
-- Ed
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Are the CEL's the first notice that this is happening or are there symptoms? Is it an issue with the new power plants? Got my wife a 2011 Forester last year.
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under certain conditions like heavy load, exhaust does get to the solenoids which causes the build up in those pics. But that doesn't mean that the same occurred under all conditions.
Maybe i am wrong and something else is causing the valve guide wear, but i have not been able to identify it. The only commonality i've found so far is the smog pump. Maybe it's just from the normal operation of the pump? I just wouldn't think that it's on long enough to cause that kind of damage.
-- ed
Maybe i am wrong and something else is causing the valve guide wear, but i have not been able to identify it. The only commonality i've found so far is the smog pump. Maybe it's just from the normal operation of the pump? I just wouldn't think that it's on long enough to cause that kind of damage.
-- ed
Again, you're probably seeing correlation and not causation.
Example: engines that have only one AIR valve or only one AIR valve fail, yet the other cylinder head has worn valve guides.
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Now take a look at this picture of the small port right behind the exhaust valve:
The transition from the valve seat into the smaller port diameter, then the transition back out to a larger diameter creates a classic venturi tube effect. This causes exhaust velocity to increase right by the smog pump port. I imagine this was done by design to aid the pump in injecting fresh air into the port. Even without the pump being active, however, if this port is open to fresh air, under certain conditions the increased velocity can create a venturi effect which will actually draw in air from the small port.
-- Ed
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Let's examine the picture below, which I do not claim to be mine:
Let's assume v1, p1 are in the cylinder, v2/p2 are at the valve seat (which can be taken to be a "nozzle/constriction"), and v3,p3 are the exhaust port. All the area shown outside the diagram is to be considered atmosphere.
One can see that the pressure p3 is greater than the pressure p2...can't argue with science...so logically any opening near p3 would allow the fluid/gas to escape to the atmosphere, not the atmosphere into p3.
Let's assume v1, p1 are in the cylinder, v2/p2 are at the valve seat (which can be taken to be a "nozzle/constriction"), and v3,p3 are the exhaust port. All the area shown outside the diagram is to be considered atmosphere.
One can see that the pressure p3 is greater than the pressure p2...can't argue with science...so logically any opening near p3 would allow the fluid/gas to escape to the atmosphere, not the atmosphere into p3.
-- Ed
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-- Ed
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I wonder what SOA does with this info, sht can it? seems like a major defect that should be recalled and corrected. Maybe they need a certain number of reported cases before they address the issue.