David '96 993

It looks like my mechanic quite possibly foiled the evil carbon deposit demons

I passed smog having had the "carbon deposit"/"check engine light"/"cold start up error code"/"secondary air injection blockage". Read on if you have, or have had or may be having this issue.

I have had my check engine light on and off for over a year now with error codes #80 and #280. My mechanic has done much research on this as I (and he) were very concerned and was resistant to pulling the head off to ream out the ports and do a valve job....You may ask why...

...Because I have not been burning an excessive amount of oil, and we both feel that the valve guides may not be an issue. I burn one quart about 2500 miles when I don't track the car.

We have all read countless posts on this topic and the car has been maintained with Techron, alot of track days and serviced by the book. We know the entire history of the car as I knew the previous/original owner.

I researched on Rennlist, called PCNA, worked with the dealership and the Regional Service Manager (to no avail...not covered under warranty...yadda, yadda, yadda). Solutions were to pull the heads, or more recently several Rennlisters have had some luck with pumping a solvent through the system to dislodge the carbon (not nearly as evasive or expensive as pulling heads ).

What did we do???

My mechanic tested all of the components in the secondary air system, ran a PST-2 and checked the oxegen sensor signals. Everything looked OK. The secondary air appeared to be reaching the combustion chamber. The only finding was a hose to the fuel pressure regulator/varioram intake system appeared weak and was pinching.

I took the car to a smog referee and passed. They did the smog test there and everything appeared fine. They gave me the and I went on my way.

What does this tell me...that the issue might not be a carbon deposit in some cases and research is needed to be done on a case by case basis before you pull your heads off, ream out ports and do a valve job$$$$$

Note: My fingers are still crossed that I don't get the error code again once the DME system cycles through again.

Agro1

Did you run a leakdown to make sure you're not loosing any compression through the valves ?

Craig MX7

David -
Couple of things.
Error code 80 comes up as "Exhaust Valve Control Circuit High (Bank 1)"*.
Code 280 is "Cylinder 7 Injector Circuit High"*Now I just know this is not right
These are not the codes that indicate the failed SAI and require the valve job. Not sure why your mechanic would even go in that direction.
Also, When you take the car to a smog referee they only check the actual emissions of the car. Since they are not checking during the first 30 seconds of a cold start, they have no way of knowing if the SAI system is functioning. They will ignore stored error codes and don't care if not all the sensors have gone through their reset cycles. This way you can simply disconnect the battery the day before and pass the smog test. Only the referee has the authority to ignore the OBD computer information and pass the car solely on the actual tailpipe reading.

David '96 993

Craig,
Thank you for clarifying the codes that I provided. These were the codes that I noted on the invoice. I have gone over this SAI issue with my mechanic several times over the last year or so. I suspect that the codes that were on the invoice could very well have been a typo.

What is the SAI error code number? I believe he had said that it was on the cylinders on the left side (per the code).

He is a very reputable mechanic with close ties to PCA, POC and many Rennlisters use him.

Craig MX7

David Yeah I figured those probably were not the CEL codes you had. The SAI codes are P0410 and P1441. I think 411 is also possible which would be the other side of the engine - but it usually comes out as 410.
As you found, it is possible to pass smog even when the system is blocked, by going to a referee station.
Craig

leeham

Mine is P0410, comes on about every 400 miles. I have an aquaintance with a code reader who can extinguish it for me. The engine was out at 51K and then again at 109K for the dealer to clear the carbon deposits and kill the light. Light returned again at 111K, with the same code. I'm trying to get Porsche to pay to get it fixed this time. It truly is a design flaw and they should own up to it.

Lorenfb

"What does this tell me...that the issue might not be a carbon deposit in some cases and research is needed to be done on a case by case basis before you pull your heads off, ream out ports and do a valve job$$$$$"

More the exception than the rule!

Craig MX7

Had the valve job done a few months ago to fix the SAI CEL problem. Avoided the dealer because I wanted an alternative to the factory guides. Job was done at a respected local shop. I asked what material or source they used for the valve guides, but was told thats a secret.
Wish I'd asked before they started the work
Anyway job eventually completed and the CEL comes back on. Still code P0410
Back to the shop. This happens 3 more times before the mechanic replaces the
"Pneumatic secondary air injection switching valve" . Now 3000 miles later the light is still off, so it looks like that was the problem. I did have high oil consumption 400 miles/quart (now 2000miles/quart) so definitely needed new valve guides, but I don't think that was what tripped the CEL. Both the mechanic and I had never heard of this switching valve. So thats probably why it was the last thing checked. Might be a good thing to look at before pulling the engine especially if your oil consumption doesn't indicate bad guides
Craig

krburrell

Craig

What is the part number of the pneumatic secondary air injection switching valve?

Thanks

Craig MX7

Keith
did not get the part # but the label on the box was
"Pneumatic secondary air injection switching valve". Perhaps somebody with a PET can look it up
Craig

krburrell

Craig,

I did not see anything by that name in PET. Do you know where the part was located?

Craig MX7

Keith-
hey I found it.
part # is 993 113 245 01 label says "Abschaltventil" and "cut off valve".
I think that "pneumatic etc. etc. " is what was written in the manual - at least thats what the mechanic wrote down for me.
Craig

krburrell

Craig Thanks!!!

leeham

Anybody else know anything about this valve? How much does it cost? My oil consumption does not indicate the need for valve guides (1 qt / 2000 mi at 126,500 miles)

Thanks,

David '96 993

Good luck with that. I agree, and even tried contacting PCNA but they are washing their hands of this issue. I was just exploring the possibility of it being coverered under the emissions warranty.

My only point is that if someone has this error code, their mechanic should test all components before they pull the heads. As Keith and Craig are finding, the carbon deposits may not necessarily be the culprets to the error code.