95carrera

Is this necessary if car is still operating okay after 100k + miles? Is it a routine maintenance item, does Porsche recommend replacing these on some routine or only when they totally fail?

​​​I'm installing Porken chips and have been reading about MAF's for the first time. Slippery slope.
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My only current annoying symptom is at very low speed, under 20 mph at like 1,300 rpm when I back off pedal I get a thud in the drive line. My other 85' automatic did this too. My only real unpleasant experience in the car. I figured it's just how they behave since both of my cars did/do this.

FredR

The auto box problem may possibly be caused by an issue with the vacuum modulator system although whether that would explain your specific 1300 rpm experience I do not know -all shifts are very harsh when there is little to no vacuum applied.

I cannot think of any reason why the MAF can or will explain your symptoms as described. When the MAF has issues it can be one of two types - total failure or degradation of reading accuracy leading to "under reading" the air flow. When the latter happens full throttle performance is affected. If you run with an O2 sensor this automatically compensates for the low reading during cruise [part throttle] operation as it tries to control the AFR.

I can also think of other possible causes for your perceived "thud". Are your CV joints on the half shafts in good condition? Ids the front flex plate damaged and all bolts in the torque tube system fully tightened?

Rgds

Fred

95carrera

Thank you. Car runs great at high rpm, no issues that I can see. So I suppose my MAF is fine? If this is a "ain't broke don't fix it" I want to leave it be. I've just been reading about MAF's due to my Porken chip purchase.

I had garage Look over vacuum lines and modulator, they said all fine so idk. How does one check for damaged flex plate?

FredR

The torque tube assmebly has two locking bolts- one at the front inside the bell housing and one at the rear just in front of the torque converter.

All models have potential problems with the rear pinch bolt if it stretches and loses tension and many of us replace this bolt from time to time. If the bolt has lost tension then residual damage can result, often with no signs or symptoms. The rear pinch bolt is accessed via a rubber grommet underneath the rear of the assembly.

The front ponch bolt is located inside the bell housing at the front of the torque tube. You remove the cover with half a dozen or whatever bolts and the inspection plate comes off. Inside you will see the front clamp and the flexplate which has three leaves and each one has two bolts fastening it to the flywheel- check the plates for cracking.

Then we have the front clamp itself- infamous for not holding and causing engine failure [TBF] on the later models. Earlier models have a different arrangement that is more difficult to setup but apparently bullet proof when done correctly- I have no idea which version you have assming yours is a 1985 model as that is about the time of transition or so I seem to remember. To be clear I am in no way suggesting this is the root cuase of your issue- nothing so far suggests such issue may be imminent but if you have a clamp of the type that is prone, then you need to eliminate potential issues with it irrespective of any other considerations.

Also check the CV joints -they are bullet proof if the boots are intact and the grease help captive but when the boot cracks [as it inevitably does every few years or so, if the problem is not cuaght and recitifed the CV joints rapidly degenerate due to loss of grease and ingress of road crap.

Let us know what you find with some pics. All the above can be accessed via the search engine- plenty of threads with pics etc.

Rgds

Fred

worf928

"Who has rebuilt or replaced MAF sensor?"

Everyone. At least everyone who wants their MAF-equipped 928 to run as it should. There's no way the original MAF is completely good on any 928 with more than roughly 50k miles at this point. They degrade due to a number of factors of which 'sitting time' is one.

That written, it isn't the cause of your "thud."

Also, depending upon the overall state of maintenance of your 928 a rebuilt MAF might
a) make it run better
b) make no change
c) make it run not-at-all.

No model year in your signature. Don't know if you're EZF or EZK.

928NOOBIE

I worked with Injection Labs to get my MAF rebuilt. They have a proprietary wire design that will outlast the platinum wires the MAF's came with originally.

I'm very happy with the work they did and they are very friendly; highly recommend.

ROG100

We sell rebuilt MAF's for $315 plus a core charge.

95carrera

I have a 1985 automatic. Yes, "b" and "c" are the problems above. At WOT it pulls strong without hesitation. So I am thinking leave it alone. This is my second 85' auto and my fourth Porsche. I had two of those rear engine things before.

NC928S4

My replacement MAF came from Roger as a rebuilt from Injection Labs. The performance is night and day. She had 141,000 miles on the clock at the time of the replacement.

Idle stability and improved gas mileage were the most noticeable. Should have done this fix sooner.

hacker-pschorr

The MAF "hot wire" is a wear item like spark plugs and wires. You want to address them before you really need it.

Wisconsin Joe

Just a thought -

If you are putting an "enhanced performance" item, like the chips or a supercharger, or anything along those lines; it's always important to make sure that the car is performing/operating properly.

MAF, injectors & fuel dampers & regulators, plugs & wires, various sensors, all of that stuff.

For example, John Speake makes chips for the S2 Euro, and I'd love to put a set into my car, but I would want to go through a bunch of things before I'd even think about them. My MAF and Temp II are recently new, but I'd want to go through the fuel system (injectors and such) to make sure they are "up to snuff" before I started asking a lot more of the motor.

worf928

Unless you MAF has been replaced/rebuilt at least once, it is almost-certainly out-of-spec. My point was that it is possible that you have two issues one of which is 'hidden' by an out-of-spec MAF. (I have seen this on more-than-one occasion.)

As above, if you are going to add performance mods, you need to have high-certainty that everything is working as it should.

Unless you have high-confidence that you MAF has been replaced/rebuilt at least once, I would suggest that you pull you MAF and send it to Kevin at Injection Labs for bench testing before you add perf mods.

bubba928

Agree with all previous posts. Good preventative maintenance and will save you problems on a "road" trip.

Jerry Feather

Rich Andrade in Mesa AZ rebuilds the MAF. He is on here frequently.

95carrera

Had a preliminary look at it today. They thought it was the transmission, hard shifting. Plan is to do fluid service to see what happens.

How do I confirm vacuum is good to tranny?