Got P1128/P1130 at idle.
 

Hey guys, I got a P1128/P1130 codes at idle. My car runs great. At idle, it vibrates a little bit, but not very obvious. Here is the freezing frame.

FUELSYS1 CL
FUELSYS2 CL
LOAD_PCT 3.9%
ETC 201F
SHRIFT1 4.7
LONGFT1 0.8
SHRIFT2 4.7
LONGFT2 -0.8
RPM 680
VSS(mph) 0

I had two freezing frame of P1128. They all happens at 680 RPM and 0 mph. What could be the problem? I assume it is MAF, O2 sensor or vacuum leak. But could I locate it more precisely? Thanks!

+1 for the vacuum leak or leaks.

By the way, the code happens every 200-300 miles. I am not sure why this happens so evenly. The same P1128/P1130 and very similar freeze frame.

Your issue is affecting both banks of the engine.
Not likely to be a problem with the O2 sensors on both banks at the same time.
MAF sensor? possibly but I don't see anything unusual in your freeze frame data.
So Go with the old automotive diagnostic adage of simplest things first.
Which would be a proper vacuum test. a vacuum test gauge cost about 15-20 bucks.
A proper vacuum test will tell you if you have a vacuum leak or not.

The reason your car idles a little rough then smooths out and runs fine above idle is:
As you open the throttle and give the engine more and more air the unmetered air "vacuum leak" becomes less and less a part or percentage of the total air taken in by the engine.
So lets say at idle (throttle closed) your vacuum leak is allowing 10 percent more air into the engine at idle then it needs. Your DME OR ECU doesn't see it because the leak is after the MAF sensor. But as you open the throttle to lets say half throttle now you vacuum leak is down to say 3 percent of the air that the DME or ECU doesn't see. So now the air intake is closer to correct for the engine load so it smooths out and runs better.
Hope that makes sense:D as I am not very good at explaining things.

I am reasonable sure you have a vacuum leak based on the info you provided.
But I could still be wrong: hard to be certain when I don't have the car before me.

Codes like the ones you are getting are due to issues that are not immediately harmful to the catalytic converters. The OBDII system has to see same code logging event back to back over two driving cycles. The first time the system sees the event that would trigger your P1128 or P1130 code it logs the event and puts it in its memory as a pending code. if the same event happens on the next drive event or cycle it moves the code from pending code to a hard code and triggers your check engine light.

This is why you can erase some codes and they take some time to reappear.

If you were having an issue that was immediately harmful to the catalytic converter the OBDII system would trigger your check engine light on the first event.
A misfire is an example of such an issue.

Thanks. It looks like the problem is much more easy now. The leak is not very obvious but actually intriguing the fault codes. Do you know how much it takes for a independent shop to fix it?

Sorry I have no idea as to costs at an independent shop or at a dealer.
I never take my cars to someone else.;)

If you take it to a shop most are parts changers these days.
Try to find one that has a person with true diagnostic abilities.
More and more rare these days and hard to find.

AOS is suspect.

At idle remove your oil fill cap... Is it difficult to remove? After removal does the opening sound like a Shop Vac? Put your hand over the opening... Is there a lot of suction?

Yes. A lot of suction. And I can hear that if I open the oil cap. The engine runs lean.

I can hear the leak is around the AOS. I may do a smoke test. Thanks!

+2
Mine (same codes - car ran fine) was unseated hose from TB to AOS creating vacuum leak

Check the connections on the AOS but most likely you will need to replace the AOS . I have replaced five of them over the years on my vehicles. When you live at lower elevations, near the coast, the AOS failure rate is high. There are very few AOS failures in Colorado.

Tim, perhaps you may want to check (/replace..?) as well the accordion tube that connects the AOS with the engine block as this plastic gets brittle with age.
.

A new AOS will come with one.

Jager, I was talking about the long accordion hose that goes from the AOS to the block just behind the driver (4-6 bank).

When I replaced the AOS on my 987CS I had to buy the accordion hose as I damaged mine..
.

987?? This is a 986 Forum! I assume Tim has a 986...???

We are not prejudice of our 987 Brothers... All are welcome here on this site. :):dance:

What does it mean if there is a suction when I open the oil cap?

If there is a lot of suction, like a shop vac, the Air Oil Separator is bad.

Is that right? Never heard of it... never seen it. From where? I replaced my AOS a couple years ago... Pelican... and it came with no hose (the updated hose). I had to purchase that separately... another ~$35.

Link? Proof? Thanks.

My local said it is the problem of an intake hose. Do they scam me?

What does your local specialize in??

The diaphragm inside the AOS is cracked.