Clogged SAI ports-where does the carbon come from
10-15-2006, 12:21 AM
#1
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Thread Starter
Clogged SAI ports-where does the carbon come from
When I was driving my 1996 993 C4S to my local shop (BHR Racing) to get a new clutch put in (lightweight flywheel!) my CEL came on and guess what....clogged SAI ports. 
My car has 50K on it and I knew it was time to spend some money to keep it right so while the motor was out I had them do the top end rebuild. The code was for ports 4-6 but we cleaned them all out. Port #4 was bad, #5 was almost completely plugged and #6 was completed jammed with black junk.
Where does all this carbon come from. We discussed the clutch vaccum, etc. but would love to hear from some of you.
P.S. The lightweight flywheel is a blast. No stalling, but still getting used to it.
Mark H.
My car has 50K on it and I knew it was time to spend some money to keep it right so while the motor was out I had them do the top end rebuild. The code was for ports 4-6 but we cleaned them all out. Port #4 was bad, #5 was almost completely plugged and #6 was completed jammed with black junk.
Where does all this carbon come from. We discussed the clutch vaccum, etc. but would love to hear from some of you.
P.S. The lightweight flywheel is a blast. No stalling, but still getting used to it.
Mark H.
10-15-2006, 12:46 AM
#4
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ok..because not too long ago folks here were saying that clogged ports donot justify a topend rebuild. First they should do and SAI flush and monitor it from there.
10-15-2006, 12:56 AM
#6
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Thread Starter
Aaron offered a flush...
but gave it a 50/50 chance at best. In fact he said if I wanted to try a flush and it didn't work he wouldn't charge me for a second engine R & R to do the top end rebuild. I decided that while they had it apart for the clutch just to get it done.
10-15-2006, 05:14 AM
#7
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Originally Posted by Mark Harris
Where does all this carbon come from.
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10-15-2006, 02:50 PM
#8
10-15-2006, 03:10 PM
#9
Also, the SAI check valve is prone to corroding enough to stick open to some degree, which allows exhaust particles to venture up into the SAI passageways. My personal opinion is that this is one of the leading culprits as, in theory, nothing could move backwards up the passageways unless the check valve leaks or there is some other leak in the system.
Review the DIY SAI check valve replacement at P-CAR.COM.
-Jim
Review the DIY SAI check valve replacement at P-CAR.COM.
-Jim
10-15-2006, 06:54 PM
#10
"Also, the SAI check valve is prone to corroding enough to stick open to some degree, which allows exhaust particles to venture up into the SAI passageways."
It's WAY upstream in the ports, thus NOT affecting the problematic areas.
Check out the pictures again here: www.systemsc.com/pictures.htm
It's WAY upstream in the ports, thus NOT affecting the problematic areas.
Check out the pictures again here: www.systemsc.com/pictures.htm