Silver993

I had been having a CEL with codes P0410 and P1411. This started about 10k miles ago and I didn't want to accept that the SAI passageways might be clogged. Fearing an expensive repair, I replaced or repaired related components, until there was no denying that the ports were clogged. Let me share what I found.

When I first got the CEL, I replaced the SAI check valve. It was totally corroded and I thought that it was surely the cause of the problem. Soon afterwards, the CEL returned.

Next, I discovered that the SAI manifold had a large hole in it where one of the “freeze plugs” had rusted out. Surely this was the cause of the CEL, since a lot of the air was likely escaping though this hole, rather than being pushed through the SAI passageways. This item was removed (not easy) and the hole patched. Again the CEL returned. Bummer...

Next, I replaced the two O2 sensors before the catalytic converter. This didn't solve the problem, so I resigned myself to attempt clearing the passageways.

As it turned out, cleaning the passageways, at least in my car, was really easy, and I should not have feared doing it.

I followed those on the board who removed the heat exchanges and drilled out the passages from below.

First, I must thank cdmdriver for his wonderful write up about this process - https://rennlist.com/forums/993-foru...t-you-can.html

The key to the job was to construct the proper drill bit. I experimented with several materials found around the house. I tried baling wire, bass guitar strings (used) from an electric bass, and finally bicycle brake cable. Others on the list have used bass guitar strings, but I had trouble with them twisting up and breaking.

The best solution was to use a bicycle brake cable. Walmart sells a kit which includes replacement brake cables and gear shift cables. The brake cables are the thicker ones in the package and these worked best.

A piece of brake cable about 12 inches long seemed to be optimal. I made two guides from the bike cable housings. The first guide was 8 inches long and was used to do the initial breakthrough. The second guide was 4 1/2 inches long and allowed me to get the cable farther into the passageway. The guide has two purposes – first, it gives you something to hold onto as you drill, and second, it keeps the cable from twisting up and allows you to push on the cable to force it deeper into the passageway.

It seems that the passages in cylinders one and two have a different internal geometry than the others. Maybe someone who has done a tear down can share if this is the case. I had trouble getting past what is likely the bend in the passageway. The cable would not go through! Unfortunately, I had selected cylinder one to start the job, and this really discouraged me, almost to the point of giving up. The trick to get past this is to reverse the drill just a burst to get through the bend and then go back to the forward setting as the bit moves deeper in.

In each of the other passages, I could get through using the forward drill direction only.

Anyway, for each port, I started with the 8 inch guide. This left about 3 ½ inches of cable sticking out, once it was fixed into the drill chuck. I drilled into the port until the guide met the port opening. Then, I switched to the short guide, leaving about 7 inches of cable beyond the guide, which allowed me to go deeper into the passageway. If you start with the short guide, the cable may twist up and it is harder to push it into the passageways.

A small LED flashlight was useful to help me see the port openings, in order to direct the cable in.

In my car, it was very easy to drill the passageways, once the bike cable tool was produced. A few had some carbon blocking the entrance to the passageway. This could be scraped off with a screw driver. Some had a bit of soft carbon in the passageway and the cable went through those easily – just a few seconds of light pressure on the drill.

Afterwards, I blew air through the passageways from above (removed the SAI check valve and used compressed air) and could feel a nice breeze coming through each port.

Hopefully, now that I have a functioning check valve and a repaired manifold, these ports will stay clear. However, if they do clog up again some day, I won't hesitate to repeat the drilling.

I've been driving a couple of weeks now with no CEL and my reader shows no codes! Nice......

Mike Pezely

That's great! Happy New Year!

C4SJOHN

Silver 993. Great way to start the New Year..........how many miles on your 993?.....

P-daddy

Nice! Any pics along the way?

MarkD

Congrats and Happy New Year!

Pretty much the process we use
Except we also use a carbon melting chemical along with the mechanical cleanout

This should last many thousands of miles, depending on oil consumption

Silver993

The car has almost 52k miles on it.

Here is a photo of the cable with the two guides and also a photo showing the SAI hole where the drilling takes place.

cgfen

great result.
congrats!!!!!!!!!!!!!!!!!!


but don't go to fracking walmart
go to your local bike shop!

osugasman

Any trouble removing the SAI valve? Did you replace it? Did you split it and use it as part of a compressed air guide? Doesn't the one SAI valve cover all 6 ports?

Thx, Brian

Silver993

Yes, the one SAI check valve covers all 6 ports. It was a real pain to get off, months ago when I replaced it. For the removal task, I borrowed a modified crow's foot, as has been discussed here on the list. I only put it back on hand tight, so now it comes off easily.
To get the compressed air in, I removed the valve and inserted a rubber tube into the opening. The rubber tube had an outer diameter about the same as the inner diameter where the check valve goes. I blew compressed air into the other end of the tube.

nels415

Congrats! I also ended up using bicycle brake cable and it got my ports cleared out.

-nelson

Slow Guy

Congrats.

I used 1/4" copper tubing to keep the cable from flopping all around when I snaked it. The copper tubing was good for guiding the cable where I wanted it.

Paul902

Great write-up, Silver993. Thanks.

M. Schneider

+1..... Man,, you don't say . . My SAI check valve was an original; 70K+ miles and 14 years of age.

Thanks again 993BillW for the loaner crowsfoot wrench....

osugasman

Mark, What carbon melting chemical do you guys use?

--Brian

Sagres74

Very nice and different from other methods I have seen! As soon as the weather improves, this will be my first project.

Thanks for taking the time.