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Is SAI port cleaning a regular schedule maintenance?
I was just told by my mechanic that my 1996 Carrera is due for a SAI port flush at 40K miles as a preventative maintenance item. My Carrera currently has 41K on the odo and so far I have not had any issues with the SAI system, no CEL nor excessive oil consumption.
My mechanic says it's easier to flush regularly, once the ports are clogged it becomes much more difficult to unclog. Is this a recommended service interval? I always thought spirited driving helps to keep the ports clean, apparently this is old wives tale according to my mechanic.......
Hi Mike,
I would not go to the expense.
Replacing the check valve every 30K miles or so is probably a good idea as it corrodes internally and if compromised accelerates carbon buildup in the Supplemental Air Injection (SAI) pathways.
Dropping the exhaust and snaking out the air injection ports is done if a check engine light (CEL) is lit and is attributable to the ports being clogged. It usually occurs once during the first 100K miles on the Odometer for some and has proven to not be an issue for others. My car has 110K miles on it and has never needed the ports cleaned.
Overfilling the oil is quite common on a 993 and is also thought by some to accelerate SAI clogging.
If you do have a CEL here is my page on the sequence to diagnose SAI-related issues. https://993servicerepair.blogspot.co...-diagnose.html
Andy
I had this done at 83,000 miles last summer after changing out the SAI valve and vacuum valve above it. The SAI valve was totally rusted and ruined. (There was no record of changing this in the extensive maintenance records for the car) That operation was difficult to say the least. Changing the valve had no effect on the CEL, so on to clearing the air injection ports. Also all 4 oxygen sensors were replaced, with no effect. The Durametric tool showed that the problem was in the left bank (1 - 3)
Clearing the ports took about 4 hours. The left bank had the problem. It was done from below, using the wire cable method with injecting carb cleaner using an aerosol straw extension (3 cans!) into the ports. The cleaner was injected via the aerosol straw up into the ports until it ran clear from the other 2 adjoining ports, clearing that side of the system. This was done after the cable was worked up into the ports using a common drill to turn the cable to break through the blockage. Cylinder #3 (driver side front-most cylinder) was for some reason clogged with carbon while the others weren't bad at all. It was so bad that it was hard to see the actual port. Crusty. Result was no more CEL after clearing the faults.
The only new parts needed were 12 lock nuts for the 2 manifolds from Pelican and 2 exhaust gaskets and 6 nuts for the manifold connections.
I myself don't see this as a regular maintenance operation but only needed when the ports are actually clogged.
Last edited by rdad993; 02-19-2023 at 10:20 PM.
Reason: typo
It seems like a potentially fun DIY, as long as your car doesn't have a lot of corrosion throughout.
Some interesting things I have read:
1. Pelican sells a kit, but it seems to me that you need more that compressed air and a solvent from above via the check valve
2. A piano wire or a cut bicycle cable seem to be the most poplar choice when cleaning from below
3. Solvents - carb cleaner, Seafoam etc - many options, perhaps mechanical agitation is the key
4. The danger zone seems to be potentially breaking one of the exhaust studs which is why things like patience and PB blaster are your friend.
I sent you a PM ref such due to like miles and living here in the Bay Area and the emission issues. Absolutely agree with your shop on driving it hard to reduce the clogging such nonsense. Actually, the harder you drive it (more revs) the more oil that can get by the guides.
Yeah- not a regular service option. I did it myself with the help of a PCA friend with a lift. The valve was really stuck and clogged, but all of the ports were clean and unclogged. Once I got the valve off, it was an easy job- but that valve is really on there! I had 110K on the ODO when the CEL light came on. hasn't been an issue since.
My SAI valve was a total pain to change as well. I swapped it out when I had the intake assembly off last winter. Ended up having to use a hacksaw to cut the top of the valve off and a half inch drive breaker bar with a socket. 107k miles. Certain it had never been done before.
My mechanic did mine, at my direction, at about 40,000 miles. All ports flushed out easily after an overnight soak. The valve was stuck just like others have mentioned.
02-18-2023, 07:45 PM
Is SAI port cleaning a regular schedule maintenance?
