peavynation

It's been awhile since I've been on the forum! I think my IMS DIY was my last post. It's been a whirlwind couple years. I finished my dream workshop complete with a lift, then promptly left San Diego and moved to Los Angeles a few months later when Disney found my resume and called to offer me my dream job as a Disney Imagineer with Walt Disney Imagineering Research and Development (I'm an electrical engineer and physicist). Too bad I hate LA and don't have a garage/shop anymore. But Disney is awesome designing the latest rides, animatronics, and technology for the parks and resorts worldwide is pretty freaking fun. Ok, on to the post.

I failed smog today, with the note: "OBDII Monitor Not Ready: Secondary Air System". In CA, you're only allowed to fail one monitor on cars newer than 2000, and it can only be the evap emissions monitor, no other monitors. My car is a 2001 C4, manual.

In the last two months I've: replaced the spark plugs, all coil packs, the AOS, water pump, thermostat, oil filler tube, and window regulator. The battery was disconnected for most of those, so all the computer's monitors would need time to gather data to become "ready" after each disconnect. I have no CEL and no codes shown on a standard OBDII reader.

I last disconnected the battery a week ago Saturday to install the new window regulator, so I have 9 days of driving to work at 28miles round trip, for 252 miles total drive-time since the computer reset.

I searched the forums upside down and backwards and figure it could one of two things:

1) I need to keep driving (some say up to 1000miles?! What??), or follow the Drive Cycle I found on a random site (see attached). I likely have not kept the car in the rpm region the drive cycle is suggesting. Attached is the cycle I'm referring to.

2) Or maybe I accidently disconnected or broke a vacuum line from the Changeover Valve #2 for the Intake SAI (secondary air injector) whole ripping apart the top end to get at the AOS. But if that was the case, wouldn't I see a CEL and codes thrown? I did the AOS work over three weeks ago, and it's never run better than it does now! So I figure a broke vac line from the vac reservoir would certainly cause issues. Or even if the line from the changeover valve to the SAI one-way check valve was broken I would also expect some sort of issue. But nada, it runs great.

What say you?


I also attached a cool vacuum diagram I found online that Ahsai here on the forum did.

(One more thing: when I did the AOS, I saw that the previous owner had never hooked up the intake resonance flap actuator to the changeover valve #1. Instead, that valve orifice was connected to the power steering pump vent tube, and the resonance actuator was not hooked up at all! WTF past-owner?? I've been running it like that for 8 years. I'm sure that's another reason it runs better now!)

5CHN3LL

It's been a while since I've seen emissions readiness issues on my cars, but I thought the emissions readiness was Boolean - true or false. Your drive cycle needs to be completed as you indicated; the issue with the secondary air injection pump is a separate problem (that will also keep you from passing smog).

I think you're correct - that you need to deal with both issues. I do not know if you can complete an emissions readiness (drive cycle) until the SAI pump is functioning normally.

Do you hear the pump running on cold start in the mornings? As you probably know, it's in the left rear corner of the engine bay and sounds like a crappy vacuum cleaner. If it's not powering up at all, check the electrical connector.

Not having the pump connected won't make the car run worse; it just keeps the catalyst from getting up to temperature quickly. If the check valve is stuck, some contact cleaner may do the trick.

peavynation

Yep, thought it could be something with the pump too, but it 'seems' normal. I hear the pump kick on when I start the car cold, and 2+ minutes later it goes off and I drive away. (For 8 years I've used Macster's recommendation of waiting to drive until the pump turns off).

Are there tests I can do to check that the pump and air valves (electric and pneumatic) are OK?

5CHN3LL

Here's some info from an old Renntech post about 986 emissions readiness:

"For some unknown reason, some of the earlier 986 cars (2000-2001) are very slow to reset the secondary air injection system's I/M Readiness flag, sometimes taking as much as 100 miles or more to reset after code clearing. People have tried a variety of techniques to overcome this, often with very limited success. If you can hear the system running on a cold start, and there is nothing else organically wrong with the car, I would just put some everyday miles on the car until you see a clear I/M Readiness test, then take it in for inspection."

So, maybe it is just a matter of putting some more time and miles on the car.

peavynation

Hmmm, maybe it is. I've put 250miles on it since the battery reset, so I would have thought it would have gotten it's brain back by now. Sheesh, what's with these cars? If that's the case (which I actually hope it is) I'll be delinquent on my smog cert by the time this thing resets!

5CHN3LL

You can pay the registration now and deal with the smog later. You won't get your new stickers obviously until you get the smog taken care of, but you can avoid the late fees by paying now.

peavynation

Very true, good point!

Ahsai

What scanner do you have? If your scanner can read the O2 sensor voltage in real-time, you can follow post #6 here to check what problem(s) is in your SAI system

https://rennlist.com/forums/996-foru...l#post11746570

Also, most scanner can read the readiness codes so at least you can read that before you even try to get your car to smog so you won't have surprises. And yeah, that SAI photo was taken by me

peavynation

Thanks Ahsai, for the response AND the vac diagram! It was that diagram that showed me someone routed my lines wrong.

I have the Actron CP9575. I was looking thru the booklet and it does quite a bit, more than my car will allow (since it's a pre-'05 car). I scanned the car and saw that "inc" next to the secondary air system readiness line, so at least I'll know when it's 'ready'. I'll follow that link and see what I find.

But my question still remains: wouldn't the computer throw a code if something was actually wrong or broken? Can one of the valves or other part physically not function and the car won't throw a code?

I have 10 days to get retested on the $60 I already paid, then I have to pay again. I want this fixed soon.

Ahsai

Re your question, yes the car should throw a code eventually if something in the SAI is not working properly but that may take some time to trip the CEL. The fastest way is to monitor the O2 sensor voltage and see for yourself whether the expected pattern that the DME is looking for is there.

e.g., if the SAI valve is not working despite a running pump, you would see the O2 sensor voltage will not stay low during the cold start.

It's also possible as Schnell pointed out sometimes you just have to put more miles on it before the SAI will be ready.

peavynation

Thanks Ahsai, this is a great data plot you have on that post! Looking at the data after I'd driven the car to work this morning, I see the same fluctuations on one set of O2 sensors, and none on the other set. It looks like that is all operating properly. See attached.


I will take a look at these numbers during a cold start when I leave work today. I can't take a datalog with this scanner and plot it verses time, but I will take manual notes of the O2 sensor's values every 10 seconds or so and plot it out.

If those numbers look amiss, maybe that's where the issue is (during cold startup), and the air isn't getting into the engine due to a bad pump (#1), bad solenoid valve (#18), or bad pneumatic one way valve (#11)? Those number are of the parts shown in the blow-apart I got from your link and re-posted below.

AWDGuy

just keep driving. it took a while for mine to get into readiness mode after my rebuild.

after I passed my emissions test, it threw a code on the way home, but I had passed at that point and wasn't all that upset. my code was related to a vacuum leak.

Ahsai

You're welcome and thanks!

The O2s12 and O2s22 are the two post-cat sensors for bank 1 and 2 , respectively (first digit after the "s": 1= bank 1, 2=bank 2. Second digit: 1 =pre-cat and 2 = post-cat). They look great for being steady at ~0.7v.

The ones that are more important for the SAI are the pre-cat sensors O2s11 and O2s21. For the SAI flag to set, the DME looks for two things:
1) During cold start, the precat sensors stay close to 0v when the pump is running. i.e., O2s11 and O2s21 should stay close to 0v (except for the first minute or so when they are warming up).

2) Warmed up engine during idle, you will hear the SAI pump turns on for a few seconds and again the DME looks for the 0v reading.

Plotting by hand is fine. The info will tell you so much about the condition of the O2 sensors, the cats, and how the whole SAI system is working.

You can disconnect the cable at the engine bay "+" jumper terminal right above the a/c compressor. Then your starter/alternator cables will be isolated from the battery.

Yes, those will be the parts to go after IF your readings are off per above.

peavynation

Excellent, thanks Ahsai and AWDGuy. I'll grab some more data, and hopefully it looks good. If it does, hopefully the car will finally ready itself after more driving. I should have scanned the car before I went to smog it, but I always figured there'd be a CEL if anything was amiss that would cause the car not to pass smog that wouldn't automatically reset within 20min of driving. Oh Porsche...

5CHN3LL

If it makes you feel any better, that emissions readiness crap applies to all OBD-II cars with emissions gear, not just your 911.