Codes came back...

[78F350]

One of my Cayennes had a leak in the brake booster vacuum hose. I have not heard of it being a problem with the Boxsters, but turns out that it's pretty common in the early Cayennes. Take a good look and listen up front around the brake booster, especially near where the hose bends.

[Starter986]

Originally Posted by 78F350

One of my Cayennes had a leak in the brake booster vacuum hose. I have not heard of it being a problem with the Boxsters, but turns out that it's pretty common in the early Cayennes. Take a good look and listen up front around the brake booster, especially near where the hose bends.

I'll add that to my my list of things to check. I'm not having any spongy brake feel... but will chase anything at this point. Thank you.

[Lowski]

If you have the capability to read real time fuel trim values that will tell you if you have a vacuum leak or not. I suggest watching these videos.

Part 1: https://www.youtube.com/watch?v=5WnM_NsOtd8

Part 2: https://www.youtube.com/watch?v=cARQ0jZZ4Qc

I had similar P1128 and P1130 codes. In the end for me it turned out to be a bad mass air flow sensor. You can see what I found in P1128 & P1130 and running fine turned into barely running engine. In the process of troubleshooting I smoked my engine multiple times looking for a nonexistent vacuum leak.

There are so many areas to check I think the cigar method would be tough even if you could get it into the engine. Create smoke and pressurize the system.

If you have an air compressor or access to one I suggest you make or buy a smoke tester. If short on time like I was, buy one from EBay made out of a paint can for about $70-$80.

https://www.ebay.com/itm/EVAP-Smoke-Machine-Diagnostic-Emissions-Vacuum-Leak-Detection-Tester-NEW/221913989725?hash=item33ab1ac25d:g:wg4AAOSwYlJW52L L:sc:USPSPriority!98125!US!-1

I hooked my tester up to a hose that runs from the right side of the throttle body to the another hose on the left side of the car. It is hose 12 on the diagram below.



When smoke testing I suggest doing the following.

1. Remove your mass air flow sensor so it doesn’t get fouled. Cover the opening with tape.

2. Remove the air filter. Cover the opening with tape and/or plastic as required.

3. Cover the air intake on the left side of the car outside with tape. This will help force smoke towards the engine better.

4. While smoking open and close the throttle body periodically by hand to let smoke into the intake and the engine.

5. Take off the oil fill cap to help draw smoke through the engine. Replace once smoke comes out.

If you have a big leak you should be able to see it pretty easy. I had small leaks at the oil filler cap and the accordion section of the oil fill tube. Those took moving the parts by hand to see the small wisps of smoking coming out.

[Starter986]

Originally Posted by 78F350

One of my Cayennes had a leak in the brake booster vacuum hose. I have not heard of it being a problem with the Boxsters, but turns out that it's pretty common in the early Cayennes. Take a good look and listen up front around the brake booster, especially near where the hose bends.

No leaks at the booster hose/area.

I've an AOS waiting to be installed. There is some suction with the oil cap off... and I believe it to be greater than that I've seen (online) of a newly installed part. Would anyone recommend anything else preliminary to installing a new AOS?

Thank you.

[Topless]

The car is running lean so it is either an intake vacuum leak or failed MAF sensor. You can rent a smoke tester at many auto parts stores and they work better than other shade tree methods.

If the MAF sensor is more than 5 yrs old I would change it.

Use an OEM fuel cap as many aftermarket caps do not seal completely.