993 ca smog, secondary air induction , check engine

[fpsoc]

Recently my 1996 993 failed the California smog test; the tailpipe emissions were ok but the "check engine"light was on, directing that a problem existed in the secondary air injection. The dealer, wants $10,000 for a valve job, the independent guy wants $3,000 to leave it for a week while he disassembles and cleans it up. Since it runs great and the exhaust gases were within spec, I knew something was odd: I disconnected the battery which reset the dash light and drove 150 miles, before trying to do a smog check. OUTCOME: I passed, either I am lucky or the battery disconnect and road driving reset the codes. I am soo happy - at least for 2 more years. FLYELLW

[Don Plumley]

You are lucky that you got the drive cycles to reset in 150 miles and it cleared the SAI CEL.

BTW, clean exhaust gasses and clogged SAI ports are very possible - that's the key issue about why no one wants to pay $10K for a top end rebuld just because of an CEL SAI.

But disconnecting the battery does reset the SAI until it shows up again - which I typically though was within 100 miles. This is an interesting data point. If your CEL comes on again, I'd like you to read the codes - if you are in NorCal we can use my reader, or go to an Autozone store and borrow theirs.

Congrats!

Don

[993inNC]

Mine does the same thing, he's not lucky, thats what happens. The SAI will trip if you start the car and leave it idle. I also leave my A/C on at start up as a way to keep the initial idle speed up. If you don't the computer will take up to 50-60 miles before it throws the light. The drive cycle instructions that are supposed to be for our cars do not work. Steady driving for good distances is the MIL light fix and the way to reset the readiness codes. I've done it a few times recently and it works the same way each time.

[kang]

How much oil are you burning? One hypothesis is that loose valve stems allow oil to seep into the exhaust port and clog the passages. If you are not burning a lot of oil, the clean-out technique is the way to go. If you are burning a lot of oil, you can still do the clean-out, but the problem will come back sooner. If you are really burning a lot of oil, you need a top-end job regardless.

You mention that it’s odd that it runs great and gasses are in spec, but you have a CEL. That’s actually the normal case with the SAI problem. The secondary air pump only runs a couple minutes at startup. The ODB-II diagnostics check for it during this time. If the passages a clogged, you’ll get a CEL. Your engine can run just fine, and exhaust gases will be fine.