Diagnostic help needed! Hot film MAF and low oxygen adaptation.
 

I need some diagnostic help on my 2001 Boxster S. I recently performed some maintenance and a few test drives later got some error codes

Maintenance:

- New spark plugs, tubes/o-rings, and coil packs. Test drive was fine no misfires, etc. I burned off some on of the engine cleaner that dripped on the cats, but no issues. (Note: old tubes were leaking, old spark plugs were for a 2.5l not a 3.2l, all old coil packs were fine, but I replaced them anyway).

- Gear oil change - drilled the aluminum pan to access the drain plug. Drained/filled no issue once the plugs finally let loose.

- New fuel filter - replaced the fuel filter with no issue. Started fine after a couple cranks to refill the fuel lines, no leaks, smells, hesitation, etc.

- New engine mount - replaced the worn engine mount with the new 987 style mount. Had a little trouble lowering and raising the engine. I put the jack behind the oil pan toward the transmission near the cable that ties the engine to the chassis. this caused the engine to tilt a little more forward when lowering and made raising it harder. It lowered 3-4 inches and when I raised it back up I squished out some of the fluid in the passenger side transmission mount. I was mad mad mad at myself for not just placing the jack on the oil pan instead. Anyway, car started up fine and ran smoother than ever.

Issue:

Car was riunning better then every, then on the third or fourth test drive, I was cruising down the highway at about 80-85 mph. I had some right front wheel vibration that I still haven't sorted out yet. Pretty sure the tire is out of balance. Anyway, during that period of vibration, the check engine light beeped and may have flashed. So i pull off the highway and looked over the car. No leaks, smoke, rough idle, noises, etc. So I drove it home slowly hoping it was just a hiccup in the system after all the changes.

The next morning on a cold start the car ran a little rough and made a little rattling on the driver side near the catalytic converter. Sounded like a screw rattling. But it went away after the SAI kicked off (i think). It doesn't rattle everytime, but something is off and its idling just a tad rough.

I got an ODBII code reader and this is what popped up.
P0102 - Hot film MAF Sensor
P1126 - Oxygen sensing adaptation, lower load range, bank 1
P1133 - Oxygen sensing adaptation, lower load range, bank 2

Thoughts:

I thought maybe I knocked something loose when I lowered and raised the engine. So I "popped" the hood and started looking around, but nothing seems disconnected on the intake or the SAI. The oil filler tube also seems fine, no big oil leaks or anything. When driving the car in and out of the garage with the engine cover off I can hear a pressure release sound when I give it gas under load. Not sure if that's normal.

I could try a new MAF sensor, but I find it hard to believe the MAF went out right during my test drive window. Is there something obvious I should be checking? I was expecting to find some kind of intake leak or blockage.

Thank you for making through my wall of text! :D

Both the 1126 and 1133 are typically an indication of an intake aire leak.

Do you think it’s likely between airbox and throttle body?

Without a smoke test, no way of telling....................

That's what I was afraid of. Here's the plan for now. Please let me know if there is a better way to do.

1. Test MAF values in live data in my code reader (if possible).
2. Clean MAF and reset/retest.
3. Assuming I still have a problem, remove intake tube, cover the throttle body and smoke the rest of the intake system via one of the connections behind the throttle.
4. Fix any leaks and clean throttle body.
5. Pray to the Porsche gods for mercy!

There is a little bit of oily build up at the connection between the oil filler accordion and the part that attaches to the engine. no drips on the engine. Could the be my culprit?

Quick update. I decided to start my pulling and cleaning the throttle body. That way there would be more room to look around for anything obviously wrong.

The throttle body is dirty (64K and probably never cleaned), but pretty clean from behind the valve and through the intake manifold. There is some oil, but I think it is acceptable. The PO said the AOS was replaced at some point. Please let me know if this amount of oil looks troubling or not.

There was also a strong gas smell from inside the intake. You could immediately smell it after removing the throttle body.

That said, there is damp residue all over the lower pivot for the resonance tube valve. I've read this could be power steering overflow and there is a small old gooey puddle of it in one of the crevices on the block. Do you think this valve could be my vacuum leak? Or this is just old power steering fluid?

Pictures

http://986forum.com/forums/uploads02...1706049784.jpg

http://986forum.com/forums/uploads02...1706049814.jpg

more pictures

http://986forum.com/forums/uploads02...1706049895.jpg

http://986forum.com/forums/uploads02...1706049952.jpg


http://986forum.com/forums/uploads02...1706049992.jpg

Have you taste it? (seriously..) as oil and hydraulic fluid taste completely different.. you don't need to drink it, just the tip of your finger will give you an accurate taste.. :)

I dabbed a piece of paper towel in it and smelled it....but it didn't smell like anything....iI guess I should have tasted it!

Here's a shot of the resonance flap hinge.

http://986forum.com/forums/uploads02...1706062969.jpg

The check valve going into the resonance tube boot is oily on the boot side. The PCV valve is also very wet/oily.

To replace to replace the check valve, is it just press fit?

Here are pictures of the PCV and check valve.

http://986forum.com/forums/uploads02...1706076098.jpg


http://986forum.com/forums/uploads02...1706076134.jpg

Do you think I should be concerned about the gas smell in the intake? Could it be a bad regeneration valve for the evap?

I would worry about the oily residue and oil saturated dirt all over the engine.
It is definitive proof of multiple vacuum leaks.

+1 Yes! The first step would be to clean your engine then start troubleshooting :rolleyes:

Thanks, I’ve been cleaning as I go by hand. I really want to spray this thing down and start fresh, but now is not the time for that. And for the record I didn’t let it get this way, but it’s on me for buying such a dirty car.

I just cleaned the MAF sensor and sucked a few small pieces of leaves off the air straightener. No oil in the intake tube, but a little dusty. MAF wasn’t too bad.

I just ordered a smoke machine. I guess we’ll see what we find.

You may want to look at the condition of your air filter while your in there.

Fortunately, the air filter is new and there were only a couple very small leaves in the bottom of the box.

I spent the last week mapping out each of the vacuum systems and AOS tubes and I think I finally understand what everything is. Smoke machine has arrived and smoke will be commencing in T minus 1hr.

Update. I smoked the intake through the AOS connection on the plenum. I only had a leak at one of the boots for plenum that I reattached after cleaning the throttle body and a tiny bit from the top of the resonance tube hinge once I cranked the PSI up a bit on the smoke machine. Fixed the boot and reattached the AOS.

Then I smoked through the oil filler tube, but had a hard time sealing it off with plastic bags, rubber bands, and tape. I didn't see smoke come out anywhere.

After making sure everything was connected, I disconnected the battery for 10 minutes and did the e-gas learning sequence. Then it started right back up no problem.

However, while the SAI was running there was an exhaust rattling type sound that went right away as soon as the SAI kicked off. At first I was pretty worried, but it ran/idled perfect as soon as the SAI kicked off...so I'm a little less worried.

The only other issue is that the oil smelled a bit like gas. I'm not sure if its a leaky injector or just from the car running rich based on the error code. but it you put your nose over the filler tube, you get some stink. You have to get pretty close to smell it.

I took it on two 20 minute test runs around the neighborhood and highway. No error codes yet but I know it's too soon to tell if I am in the clear. There is definitely something going on with the SAI/exhaust. There is no exhaust smoke on start up or during driving.

I'm out of diagnostic time for a bit while we work on our house, but here is my current plan.

1. Back the car on race ramps, start it cold, climb under to see if there is something obvious going on with the exhaust.
2. Remove the engine cover, start it cold, and see if there is something obvious going on with the SAI.
3. Test the fuel pressure to see if the fuel pressure regulator is going bad. This is what caused similar fuel trim codes in of the "arrowhead garage" videos on youtube. He's got some helpful videos.
4. Possibly remove and clean the fuel injectors....does not sound fun, but could be good to do anyway.


Sorry, no time for pics right now, but I took a bunch.

Had an about an hour to some more diagnostic work. Jacked up both sides of the car and banged along the exhaust from heard to tail pipe on both sides. It’s definitely the drivers side of the muffler, probably the top mount.

I took it on a 30 minute highway ride to run cycle the battery/fluids since it’s been sitting for awhile. No noise on start up, but some exhaust rattle at idle. Still no check engine lights, but I didn’t really push it.

Another update. I've taken the car on 5-6 runs and the check engine light hasn't come back. However, I'm experiencing a slightly rough idle and slight hesitation around 4k (almost feels like power surges). Looking around I found someone on the pelican forums with the same issues.

https://forums.pelicanparts.com/boxster-cayman-forum/600891-bought-durametric-but-i-need-help-understanding-numbers.html

I checked my fuel trims and they are almost identical to what this person had. The fix for them was a new MAF. I'm going to order one and give it a shot.

Note: I also did the oil cap test. I took it off with the car idling. I was able to remove it no problem and the car immediately began to run poorly....so I think the crankcase vacuum is okay.

Update: new Bosch MAF sensor is in and I reset the fuel trims. I’ve taken it on 4-5 medium trips and the fuel trims are now FRA 1.05 and RKAT -0.42 for bank 1 and FRA 1.02 and RKAT -0.42 for bank 2. A lot better than the 1.28 and -3 I had before.

I need a few more spirited drives before I declare victory. But it feels pretty nice!