rpaitich

My '96 993 just put up the dreaded P0410 code and Check Engine light. I cleared it with my code reader, but I'm puzzled.

As I understand, the P0410 shows up when the air pump is running on a cold start and and O2 sensors detect excessively rich mixture. When I got the P0410 this time, I had been driving at highway speeds for a few hours, and the CEL came on while I was driving.

I cleared the P0410 and the CEL light went off and I've driven over 1000 miles with no CEL.

Two questions:
* Why did the P0410 get posted on a hot engine?
* Why didn't P0410 show again, after I cleared it?

JB 911

try a search for a sai post by user bruce 7 type like bruce7 sai cel or something. He had a similar sounding symptoms and posted a good diy.

Have you already replaced your check valve?

Richard C2S

How many miles are on your engine?

rpaitich

JB: thanks; I found two SAI write-ups by Bruce7; good stuff.

Richard: my 993 has 76K miles now.

Ron

Richard C2S

Thanks, Ron. I'm trying to get a sense of when/where the SAI thing is most prevalent. High mileage cars? Low mileage rarely used cars? All cars that are used frequently for short trips and/or in stop and start traffic?

We get posts from the guys who suffer the dreaded SAI problem. We don't really know whether it afflicts every 993 or just a small percentage.

Kika

I can't answer the question as to why it came on when it did, but I can say mine did the same thing when I first got my car. It came on on the FWY exit ramp as I was decelerating and downshifted. Not sure if any of that was related, but the engine was pretty hot after an hour of hwy speeds.
Anyway, I reset it, and it stayed off for a while.

My THEORY, is that since the OBD II was a new system in 1996, they (Porsche Engineers) did not really know the range of values that should be used to trigger the CEL, and since they needed to get the system to pass US emissions, they set the values with too narrow boundaries. I personally believe these cars will run fine well beyond the boundary conditions of the OBDII system for throwing a CEL. We the consumers are suffering from it, but Porsche needed to get the cars certified for sale, and move forward.

When my CEL comes on, I check the code, note it in a book, with the mileage, reset it, and move on.

MOST of the time, I chalk it up to some parameter wiggling out of bounds and the OBD II getting all b*tchy and deciding to throw a CEL. If it is something chronic, the light will come on again and the some code repeated. My tolerance for CELs has grown to the point, where sporadic ones (every few thousand miles) do not even bother me. When it becomes chronic, or the car does not run well, is when I start to pay greater attention to it.

Steve Weiner-Rennsport Systems

A few thoughts,....

'96 cars had very tight OBD-II limits and were more prone to occasional CE issues than the later cars. Readiness Monitors were/are especially challenging to reset.

Intermittent SAI codes can be also attributed to severely corroded SAI check valves and this is something I'm recommending 60K replacement, based on my observations.

SAI passages do become obstructed over time due carbon buildups caused by oil consumption and that's something to keep track of. Worn guides are the culprit and when we do a valve job, we open the SAI passages in the heads a little bit to help prevent a recurrence. Along with good guides (not factory!) and proper fitment, these issues do not return.

Naturally, JMHO.

Richard C2S

Steve,

Were the OBD limits or parameters changed for the '97 and/or '98 cars? Do I assume correctly that the valve guides weren't changed for newer cars, meaning '97 or '98? I can't tell from the posts whether the dreaded SAI problem afflicts a greater percentage of '96 cars than '97 or '98.

Thank you.

Steve Weiner-Rennsport Systems

Yes,....loosened a bit.

Every 911 engine since 1978 has used the same (soft) guide material; even the GT-3's use the same stuff. The SAI issue affects all of these OBD-II cars, equally.

Richard C2S

Steve,

Thanks for responding. I guess it was wishful thinking that Porsche made some changes along the way so that "newer" 993s wouldn't be as susceptible.

axl911

So the GT-3 and 996TT engines are susceptable to the dreaded valve guide wear???