Hi all, I used the forum's search feature and got this note from Scott Slauson, which it would seem to explain to all but the thick-headed like me what the secondary air injection system, how it works and especially how it can effect the performance of our cars. I seem to need extra help in having explained to me how the secondary air injection system can effect the performance of our cars? Here is what Scott Slauson said:
"The most common problem with all the Secondary air injection systems is the cut off valve or the check valve up to 1999. The cut off valve is vacuum actuated by a solenoid. When actuated it allows the air to flow to the exhaust ports in the cylinder heads. To keep the exhaust gasses from going back into the air pump and damaging it the check valve blocks it off.
This valve is what they call a one way valve. Both of these valves are actually the same as what was used in the 993's. Having said that we can find a direct correlation between both of these cars having the same problems. Generally the 993 will require the check valve while the Boxster will use the cut off valve. From 2000 on the Boxster uses an improved version that combines both of these valves into one unit.
In the Boxster the air pump is located on the passengers side under the engine cover. The hose that comes off of the air pump goes to the cut off valve unit up to 1999 or the combo cut off valve from 2000 on. On the 1999 and before years there is another hose from the cut off valve that goes to the check valve."
The reason I am asking is that I am chasing a CEL that has led my mechanic to try swapping out the ECU with another used unit. He says that when they put in the new (used) ECU, the fuel mixture was perfect, but the secondary air injection system was not working.
The problem is that the pump does not kick on when the car is cold. (the pump is OK and has been tested with Porsche Tester 2). It seems that the pump will not work with neither new or old ECU.
The car is actually running fine and putting out better than 200 hp to the wheels, but that darn CEL that continues to come up is driving me nuts. After looking at the cats, MAF and oxygen sensor, we have tried swapping out the ECU.
Any thoughts would be appreciated (mothers tell your children not to mess with any cat-back exhaust mods unless you like to work on your cars....)
Ed
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