Well every once in awhile I would get the PSM and ABS light on, After a little searching I've come to the conclusion it could be a handful of things or mainly the MAF. Am I correct to believe my MAF is the culprit when I performed this test?

PSM and ABS light turn on
Car starts Blogging and revving up and down like a vacuum leak.
I unplug the MAF and nothing happens. No Drop in idle or anything.

According to this test, Is my MAF dead? Weirdly enough the car stopped revving up and down when I unplugged the MAF.

Safe to say I need a new MAF?

 

Could also be a boost leak, if you have a hose that is bleeding off under pressure you will get that same problem or fault.

 

Engine Guy, Would this be true if the car was just idling and the PSM/ABS came on in a scenario? The lights also turn off when I shut the car off and turn it back on.. Could it still be a boost leak?

 

Yes it still could be, if it is not a major leak like main intercooler hose it would not really trip again untill you gave it some throttle.

You can always try cleaning your MAF sensor to see if that helps. Use some MAF cleaner or some CFC free electrical cleaner or mild brake cleaner. One of the best cleaners for this kind of stuff is the Honda brand. It works super yet it is not harsh at all. You can literally spray it in your eyes and it will not really hurt at all. Normal brake cleaner or electrical cleaner would practically blind you.

Hopefully some others will add info here, as well as I know engines I am still learning much of the more Porsche specific info.

 

The time the ABS/PSM goes on is completely random, sometimes its during a stop, sometimes its while cruising (no boost) on the freeway at low rpms. I have tried a CFC cleaner and noticed im not running the OEM paper filter. I will try to change to paper filter and clean the MAF again. Is this a good start? Keep in mind I have cleaned the "performance filter" and MAF already once and it has come back on.

 

The easiest way to check MAF of you don't own a durametric cable is run a test using a voltmeter and a sewing pin. There is a DIY I think on renntech.org ground to fuel filter, lift rubber boot off MAF and I I believe the wire u want to measure is blue/white?(it's furthest away from you, there are 4 wires feeding the socket. You take pin, and push it into wire where it meets head of socket, set meter to read volts, make sure you have ground. I think the voltage when warm at idle is 1.4. Someone else here can conform, or the DIY is more specific.

 

Your post is a little confusing. Maybe the fault is mine.

You write:
"I unplug the MAF and nothing happens. No Drop in idle or anything."

Then 2 sentences later you write:
"Weirdly enough the car stopped revving up and down when I unplugged the MAF."

One shade tree like test of the MAF is to disconnect the MAF at the wiring harness (do not remove the MAF from the intake system this just creates a big old intake air leak) and see if the symptoms go away.

But first....

The MAF supplies data that is used by the PSM and ABS systems.

If the MAF is acting up these other systems are affected and turn on their warning lights to let you know these safety critical systems have compromised functionality or possibly even non-functional.

As I opened with, one test is to disconnect the MAF and see if the symptoms go away.

There are I'm sure -- and as some else mentioned -- electrical tests but I do not have these test steps at hand.

Back to the MAF disconnect: But there's a bit more to this: Disconnect the MAF at the wiring harness, then clear error codes, even if there aren't any. This resets the DME's learned fueling/etc back the factory defaults. This is important for they may be horribly wrong if the MAF is bad. If they are not cleared the engine may run as bad as before and fool you into thinking the MAF is not to blame when it is and the untoward behavior arises from the bad learned fueling/etc.

Then drive the car as close to the same way as before when the untoward behavior appeared.

However, I'm always a bit reluctant to recommend someone drive the car if there's a chance of an intake air leak.

Part of me dismisses the odds of a boost leak being present for the engine is not making boost at idle when the symptoms appear.

But more on this below.

Intake leaks: Now I used to trouble shoot/id intake air leaks using an aerosol can of Carb cleaner (tells you how long ago I did this) spraying this stuff as suspected intake leak areas. If there's an intake air leak the engine will react to the carb cleaner.

The trouble is the intake system of this car is hard to get at.

What was done last?

Sometimes, more times than not, the last thing touched is suspect.

Which brings me back to the boost leak: If the boost hoses were off and then put back on what the techs tell me can happen is a small section of the edge of the hose gets folded back a bit and this can create a boost leak or even allow the hose to come loose which is a huge boost leak.

The techs use some kind of hose compatible lube to avoid this.

So, if you tell me the boost hoses were worked on recently...

I can't say for sure you need a new MAF. I replaced a MAF on another Porsche and my diagnosis was wrong. It was an oil filler tube cap leaking that was the cause of the MAF.

However, this replacement MAF eventually went bad, and I was more circumspect in my diagnosis and I was able to reinstall the original MAF which of course was not bad to begin with and which still functioned even though it sat in a box for several years.

The symptoms do not point to the MAF conclusively, but they do strongly suggest the MAF is bad.

However, a new MAF is expensive and if I were you I'd be reluctant to buy a new one without more proof it needed replacing.

So, you either need to do more diagnostics, more tests, to either confirm the MAF or eliminate the MAF as the cause.

Sincerely,

Macster.

 

Thank you Macster for the excellent instructions. Will give it a go and see what happens

 

Another common issue is a leak in your expansion tank lid letting coolant leak onto the wire harness and ground out the MAF. Pull the plug and look for any signs of corrosion. I've personally experienced a hairline crack in the cap that would only let the coolant out in the form of vapors when the car was hot... Took awhile to figure out where it was coming from since it would only do it after the car was up to temp.

Good luck.