CEL codes P1128 & P1130
 

Hey all -

So about a week ago codes P1128 and P1130 popped up on my car. I did some research and found that a dirty throttle body / MAF might be the issue. I got to the engine and cleaned the TB (didn't do the MAF because I realized I didn't have a security torx bit), reset the computer by disconnecting the battery, and was good to go.

Drove the car for another week and today the CEL came back - same codes. Obviously, the MAF might be an issue to look at, but what else should I be looking for? I tried taking the oil cap off while idling and it was really difficult - I could eventually lift it a bit and get a vacuum "hiss" but I cannot physically take the cap off with the engine running. Is this indicative of an issue? AOS?

Thanks for any help...

Get the proper tools (Torx) and clean that MAF. Go to Harbor Freight.

That tight oil cap... leads me to believe it is an AOS preparing to wonk on you.

Clean that MAF.

Or if you have a Dremel, grind some slots into the torx head and use a screwdriver to take them out.

I cleaned the trottle body and the MAF, then replaced the MAF, checked and replaced the throttle body gasket and oil filler cap and every time I reset the codes would come back. Kinda running out of ideas and then I noticed a crack on the underside of my dipstick tube. The tube was brittle and when I took off the upper part that goes thru the bulkhead it just broke in two pieces. I replaced the tube (very easy and not expensive). Since then no CEL codes.

I just bought a Torx set - I'll clean it tomorrow hopefully. Are there any other signs of the AOS? I get a little bit of white smoke on start up but no more than a few wisps and then none at all.

Interesting idea - I'll have to check that. I'm hoping it is something that simple. I'm probably going to sell the car soon and I want it all working properly.

Speedy, I too am having the same codes and it started just two maybe three weeks ago. I've done the same things you have, cleaned the MAF, checked for vacuum leaks, checked the oil cap, replaced all the coils, and cleaned the throttle body. Once I clear the codes, about 50 miles later they come back. I am currently late on the smog test due to the CEL and monitors not clearing.

I'm wondering if the low humidity we have been having in the last month could be the problem. All summer long I've had no CEL, but two weeks ago they popped up when the cooler dry air came in.

Anyone else have this issue?

When I got these codes it was because of a poorly seated AOS to TB hose. I had removed to clean the TB and Pipes and I didn't seat it back properly. I think you have a vacuum leak unless you have a defective MAF. But people do have issues with the Oil fill and dipstick tubes. Any where a vacuum is present for both banks.

As far a AOS vacuum, the quickest test you can do is remove the Oil fill cap while the engine is running to see how much vacuum you feel there. Should have some but not overpowering.

"If" your MAF sensor is the problem cleaning it doesn't always correct the problem.
Perhaps it needs replaced????

As to your question about low humidity.
the MAF sensor accounts for changes in humidity when it is functioning properly.

Blue,
The MAF is only 2 years old, along with new O2 sensors. What I tried today was cleanning the throttle body and recalibrating it. It seemed to fix the CEL coming on after about 20 miles of driving. I now only have the SAI monitor after driving about 40 miles. Hopefully I can continue driving it so I can reset the last monitor with no CEL. Then I can get the smog finally and hopefully it passes.

With those two trouble codes, P1128 and P1130, the AOS is also suspect.

There is a spec for vacuum at the oil filler cap. It Has to be read with a manometer as a regular vacuum gauge is not calibrated fine enough. I do not know the spec but if it exceeds the spec then the AOS is suspect. This info has been posted by member "JFP in PA" so if one does a search you should be able to find the info.

I just went and did a search under manometer.
The spec calls for under 5in/wc at operating temp.
You need a manometer and an oil cap with a fitting for the vacuum hose.

I have had these codes for a while. I cleaned the MAF and helped briefly. I finally bought a used one on ebay a few days ago and so far the codes are gone.

If its that hard to remove the oil filler cap you have a dead AOS. Replace the AOS and see what happens. When the membrane in the AOS splits, which yours already has done, you have a vacuum leak. fix the known problems first and then you can start working on the unknowns.

This seems an appropriate thread to ask a question.
Aftermarket maf from ******************************** az, rock auto, or basically ANYBODY, is worth about $75.
Pelican has "bremi" for $130, or Bosch for $225, or PORSCHE for $675. Yup.

What are y'all using with good success? Last thing I need is to stick in a junk maf and not fix my problem, Haha.

Sent from my SM-G970U using Tapatalk

I bought a Bosch MAF off of Amazon it fixed my P1128 and P1130 codes. I didn't have any luck cleaning my old one. The MAF that I replaced was a Bosch unit that the previous owner had installed at dealer just before I purchased the car. It failed in about 6000 miles and 4 years.

You don't specify the year of your car.
I think Porsche used the hot film type MAF up to 1999
In 2000 they went to the wire type MAF.
)
Bosch developed the wire type MAF so I go with Bosch for the Wire MAF.
Not sure if they developed the hot film type, and I don't have a car running that type.
So I have done no research on that type MAF other then how they work.

As a rule of thumb when it comes to sensors I try to find out who developed them.
I try to stay away from copy cat sensors.

But in the end do your testing to make sure your MAF is your problem.
The Porsche MAF is a Bosch even has the same parts numbers I hear.

Thanks for the thoughtful reply.
The car is an '03 S. I just installed a motor from an '04 S. Had an odd "flat spot", put the factory tune back in, same thing.
Unplugged the MAF, problem went away.

??

Sent from my SM-G970U using Tapatalk

Unplugging the MAF on a Porsche seems to work as a test of the MAF for the Porsche.
I did that to test a friends Ford pickup. Truck would not even start with the MAF unplugged.

Your 03 S should have the wire type. They can be tested with a multimeter but I don't know the values. I do know they are more sensitive then lots of people realize.
You can mess them up just by touching the wire with your fingers new from the box.

You could go to YouTube and look for testing methods of MAF sensors.
If you want to be more confident it is the MAF before replacing it.
Scannerdanner is very good and has tons of info on diagnostics.
he will have numerous videos on MAF sensor related issues.