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.

They used to... The AOS came with the accordion shaped hose.

I have not replaced an AOS in the last 4 years so things must have changes. Does not surprise me, the parts suppliers look for more ways to gouge us.

Shows the hose in the photo:

https://www.pelicanparts.com/More_Info/99610702304M100.htm?pn=996-107-023-04-M100&bt=Y&fs=0&SVSVSI=1048

I see my confusion. I thought you were referring to the hose/tube that connects the top of the AOS to the intake... and I was wondering what you meant by "included". Then I saw your post and realized you were talking about that hose at the bottom of the AOS... yes, the accordian. That and the clamp seperately I purchased. Fromn Pelican. ;)

That top tube I had to replace because the AOS had been redesigned since the original. That tube cost me ~$35. I had a fix in place (the original tube with a section cut out and a piece of hose clamping the two pieces together). My OCD took over and I couldn't stand that ugly part snaking across the top of the motor.

:cheers:

They specialize in volkswagen. Here's the pictures of the leaking hose they said. I am confused that these hoses are before the MAF. The air should be adjusted. Thanks for any help!
http://986forum.com/forums/uploads02...1596848125.jpg
http://986forum.com/forums/uploads02...1596848133.jpg

Tim, You might have other vacuum leaks besides the AOS. If your mechanic did a smoke test he might have found a cracked hose(s). BUT, if you have major suction at the oil fill tube the AOS is bad.

Yeah. I did see a lot of signs of AOS failure. Like, the car runs rough at idle only when it starts from cold.

I am just curious that does the fault code relates to the failed AOS or the leaking hose.

Yes, a bad AOS will trigger those fault codes. I have seen it a few times.

Thanks. I am gonna work on those. I just replaced the engine air filter. Some oil residual on it. Another sign of failed AOS?

You shouldn't be seeing oil on the air filter unless it was a K&N reusable filter, Tacky Oil is used on those. I can't imagine someone spraying tacky oil on a paper filter... but???

A bad AOS will cause oil in the intake cross-over tubes. One of the signs of a bad AOS is smoke at start-up... Have you experienced that?

Tim, you're getting good help here from Jager, so I hesitate to interrupt.
However:
I have seen oil (in small amounts) get to the air filter due to a bad aos, when combined with a poorly running engine.

Under normal conditions air only moves in one direction through the intake tube. However: if your engine "backfires", even just a slight stutter or a cough, then yes, you can see air moving the other direction, though only momentarily. I wouldn't worry about it at all, for the moment, as you could end up chasing squirrels that aren't there. I would focus first on your AOS, then on your vacuum leaks.

Then let us know how it goes.

Sent from my SM-G970U using Tapatalk

No doubt backfires would throw oil onto the air filter if you had oil in the intake/throttle body. I have not seen that since I have never had a Porsche motor backfire.

So Tim, has your motor backfired??

I think I never experienced that. But you are right, I used K&N air filter!

There are no hoses that enter the intake before the MAF sensor.
If there is a vacuum leak in the hoses that you are pointing to, then that air is not adjusted.
The vacuum leak in those hoses is part of your problem.