When you disconnect the MAF...

Ok........My car is a 2000 base boxster. I go to start the car , It turns over starts then stalls. I contacted Driving source for a new MAF sensor. The car had a 986.606.125.00 MAF in it from the factory. Driving source looked up my VIN # and said that I need MAF part number 986.606.125.01 to replace it.

So I put the new MAF in and the car does the same thing.......Stalls out ! The car's check engine light is not on either. Car car will start and run perfect if I un-plug the wires at MAF sensor. Of course I have not drove or ran the car to long with the MAF sensor un-plug in fear of damaging some thing.

Any suggestions............
Thanks, Alan

... will not harm the car.
The engine management system will just run with it's default mode and will not alter the mixture when conditions change.
This will make the mileage drop a bit, but it won't hurt anything. I know, I had my MAF disconnected for several years.
There are several factors that can cause the symptoms in your car.
A bad engine temperature sensor, a broken sensor connection, issues with the secondary air injection system, etc.
Connecting a PST-II or a PIWIS system to the car can help clarify which condition is causing the symptoms.
Take it to a knowledgeable tech.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

I've been fighting a CEL and recently replaced my MAF sensor and luckily for me it was successful. Did you disconnect the battery after installing the new sensor? I disconnected mine and then followed a process where after you reconnect the battery you turn the key to the on position (don't start the motor) and leave it on for about a minute, then turn the key off. My car ran a little weird for the first mile or so, then perfection.

But maybe it's not your MAF sensor at all. Might be worth checking the fuel pressure. I defer to the more experienced experts on this site so take my advice with a grain of salt.

Yes ....... I did all that......Still stall out. I don't think it's anything with the fuel pressure as the car runs fine without the MAF plugged in.

I've had this happen to me a couple of times at the track. Both times it was a cracked oil fill tube letting in excess air.

--- Tom

Huh........I'll check that out. So you had no check engine light come on also ?

Generally, a stalling car will throw tell-tale codes. If the MAF was off you might see mixture codes or "implausible reading" codes from the MAF. It could be an 02 sensor. Or a vacuum leak. Or a fuel pump. or..... So get some diagnosis first.

Absent that, no one can tell you if a MAF or anything else is good or bad.

Grant

Ok..........I have a strong feeling both of my MAF's are totally fine. The one I just purchased and the one that was in the car since new. A person told me it was probably the MAF as I was running an BMC air filter. He believed that ruined the MAF. But I never over oiled the filter.

because teh filter is not as effective filtering out dirt/dust with no oil.

It is possible that this load of dirt/dust passing through the un-oiled filter has did ruin the first MAF. However, I find it hard to believe it would have this same negative effect on the replacement so soon after the new MAF was put into service.

My advice is to either oil the filter (properly) or remove it and go back to the stock filter.

Do not throw away either MAF. I replaced a MAF (due to an incorrect diagnosis on my part) and years later when the replacement MAF did go bad (correct diagnosis on my part -- experience is the best teacher, but the most expensive) I grabbed the old MAF and it worked just fine. Still is working just fine.

As for the stalling.... If the stalling goes away with the MAF disconnected... this points to the MAF.

However, if the previous MAF was indeed bad the adaptation values mgiht be so out of whack you should consider clearing the error codes (even though none are present) using an OBD2 code reader. This clearing of the error codes causes all learned fueling back to their defaults.

Sincerely,

MarcW.

Marc,
I did have to air filter oiled right. Think you may have mis-read that line. I got the BMC way back in the Boxster Board group buy days. So it's been in the car for years. I have clean and re-oiled with care from time to time.
When I put the new MAF in I also put in a stock clean air filter back in. Same thing , Just stalled out and I can't drive the car or anything.
It would be hard to think this second MAF would also be bad. I got it of Driving Source which is a good company I hear.
I think I'll atleast get a code reader and and clear the codes at this point. At this point there is no check engine light on.
Thanks, Alan

Quote
Blackboxst
Marc,
I did have to air filter oiled right. Think you may have mis-read that line. I got the BMC way back in the Boxster Board group buy days. So it's been in the car for years. I have clean and re-oiled with care from time to time.
When I put the new MAF in I also put in a stock clean air filter back in. Same thing , Just stalled out and I can't drive the car or anything.
It would be hard to think this second MAF would also be bad. I got it of Driving Source which is a good company I hear.
I think I'll atleast get a code reader and and clear the codes at this point. At this point there is no check engine light on.
Thanks, Alan

installed (correctly) and connected to the engine wiring harness and runs ok with the new MAF disconnected I'm going to have to suspect the MAF, first, mainly because the alternative is a bit more scary.

The other possibility is the wiring connector/harness or even the engine controller (DME) has suffered some damage or wear or failure and a perfectly good MAF's adapation value and other info (intake air temp) is getting interfered with and this cause the engine to run poorly.

One possibility is the intake air temp is incorrect -- either way too low (or too high) or possibly even implausible -- and because of this the DME does not provide the proper fuel air mixture. If the intake air temp is reading high falsely, then the mixture will be too lean for the ambient temp and the engine can stall out with possibly some backfiring through the intake (lean engines do this). Or at the other end if the intake air temp is reading low falsely, then the mixture will be too rich and the engine's behavior can be to stall out. In this case there'll be no backfiring through the intake. The usual place an overly rich engine backfires is through the exhaust but if the exhaust is cold the unburned gasoline may not ignite. But there can be a very strong odor of gasoline about the rear of the car.

If you had an OBD code reader/data viewer you could view the current and real time intake and coolant temperatures that the engine controller works from along with the short and long term fuel trims which are in some respects reflections of the adapation the engine controller is doing based on the info supplied by the MAF (along with the #1 and #2 OS sensors).

Sincerely,

MarcW.

Maybe I'm wrong but I think that your 2000 Boxster doesn't came from factory with a 125.00 MAF. It probably came with a 124.00 series MAF. If it's the case, going from 124 series to 125 series need a DME update or reflash but going from 125.00 to 125.01 don't. Maybe it can be a good thing to plug a PST2 and see if the DME have been reflash to accept 125 series MAF... Maybe somebody on the forum will agree or disagree?



Thierry

... Porsche made the change from the 124 to the 125 in mid-year production of the 2000 cars.
It could very well be that Blackboxst's car had the 124 and the DME will not recognize the 125 until it gets remapped.
That could explain why both MAFs don't work. They're both 125s.
Blackboxst should try plugging in a 124 to see if it runs.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

According to driving source and I also looked up my VIN # and it came with the updated 00 MAF. It sez the replacement part is now the 01 with no flash change needed ? So I don't know.

What is the part number on the old sensor?

My first post I mention what MAF was in my car from the factory. And the new one that in there now.
Thanks, Alan

How long did you drive the car with the 125.00 MAF? Wondering if the car is new to you and someone threw in a MAF just to get it sold and it wasn't the right MAF for the mapping in the ECU. Could happen but not likely if the car has any history of running right with the 125.00 MAF in it.

Hah.......
I purchsed the car new with the 00 sensor installed by factory in 2000. After my car sat this winter I went to start it and it stalled out repetedly. The start timer then went to one hour. So I unplugged the battery Let it reset. Then put in the 01 MAF sensor.

with either MAF connected and yet disconnecting the MAF cures the symptom, I'm going to have to say 'mice'.

They got in the car while it sat and have done some damage to the wiring harness with their gnawing.

You'll have to expose the engine and at the same time get the car in the air and look for signs of rodent presence. Look on top of the engine and look on top of the panels that cover the underside of the car. These act to catch all the trash rodents shove out of the nest.

If you find signs mice have been in the car chances are very high you'll have to take the car in to a dealer's service department for a professional assessment of the damage. I've seen cars with mice (rats) gotten at so bad that the engine had to be removed to get at the engine wiring harness to replace it along with some hoses and lines on the engine the critters chewed up/through.

If rodents is found to be the cause of the symptoms, and there's damage to be undone, check your homeowner's insurance policy. The car may be covered.

Sincerely,

MarcW.

... but maybe the crankshaft position sensor.
I had a customer that had mice short it out and the symptoms were the same.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Thanks I'll have to check that out ! I've never seen mice droppings in my garage but anything is possible. Soooooooooooo...........If that were the case like your customers car. Would the car run fine with the MAF unplugged like my car does ? And would a ODB 2 reader confirm that or just give me a more of a general idea.

Thanks, Alan
West Reading Pa.

... the ECU runs in "safe mode", which means that it has a pre-programmed mode to run the engine.
I'm not sure if that overrides the crankshaft position sensor. Probably not.
I've never tried it.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Bad MAF will make the car run bad, and create intermittent stalling, but shouldn't make the car impossible to start and keep running.

Pedro is right about the crankshaft position sensor. Could also be the cam position sensor - the harness connector is easy to knock loose when working in the engine bay. Could also be the Throttle Position Sensor too, but much less likely. Could also be your O2 sensors - if they are bad (could be caused by driving through a big puddle and splashing them when they are hot) then your DME will get all kinds of bad data about fuel mixture and may lean the car out. Another potential issue is the fuel pump - could be getting enough into the line to start the car but not enough to keep it running. Another possibility is bad coils - one bad coil and the car runs like poop. Two or three bad coils and it is unlikely the engine could overcome the compression from the 2-3 dead cylinders.

My recommendation is that before you mess around with the MAF anymore or start fiddling with other sensors, go to AutoZone and get a $50 Actron or Durametric code reader. Even though your CEL isn't on (and it wouldn't be if the engine isn't running for more than a few seconds - not enough time to trigger a CEL) doesn't mean the DME isn't throwing codes, and these codes are your first link to what is wrong with the car - misfire? Bad O2 reading? Bad MAF/VAF reading? CPS sensor bad? Cam sensor bad? etc. If you have no codes, then I would suspect the problem is mechanical (fuel pump) or perhaps a malfunctioning alarm control unit (under the driver seat - known to get wet).

Also, be prepared for it to be more than 1 issue - I had a problem with my O2 sensors and MAF simultaneously that made diagnosis difficult until I really spent time checking codes and repeating.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

Yes........I need to get a code reader. But I was at the auto store yesterday and I asked the parts guy if the reader would read a code even if the CEL wasn't on. He said no but I have a feeling he doesn't know what he is talking about . Am I right.............

Pending codes don't illuminate the CEL but they can be read by a standard code reader.

You might check the following:
-major vacuum leak(intake, aos, oil filler cap, etc.)
-fuel pump fuse, along with replacement of the filter if it has not been done in 30k, check fuel pressures(rest/running)
-ignition switch(doubt it is this, but weirder things have happened when they go)
regards

I hadn't thought about the ignition switch, but that's a good one to add to your list of culprits.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

But the car runs with the MAF sensor unhooked

I am having the same problem with a 2000 Boxster S with 153k on it... it starts then dies immediately and my e gas wont work.. If i disconnect the MAF it runs and i can drive it but its not quite right... I did change the maf and it did not help.. I just changed the water pump and it ran fine until i let it off of the jack and put it all back together lol... thanks for all of the help...