Changed MAF, No Change!!

To refresh my problem last week............ Drove car all day last Thurs. without any problem but late in the day when coming up to a stop sign engine stopped. Started right up but wouldn't idle. Had to keep rpm's at 1500 to keep from stalling. Nursed it to my indy, put Durametric on it and only fault registered was MAF sensor. Ordered one , installed it yesterday and still same problem, won't stay running at idle. Cleared fault code, drove it for 5 minutes, back on Durametric and gives same fault. Any ideas? thanks Pete

Did you disconnect the battery? IIRC I read from somewhere that it's requred for teaching Motronic it has a new partner.

Vacuum leak?

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What was/are/is the error code(s)? If codes cleared no need to disconnect battery. Clearing codes resets long term fuel trims back to defaults. Post the codes. And you probably should avoid driving the car. Might be AOS and this can present risk of serious engine damage if you keep driving the car. You can sometimes eliminate the MAF from the list of suspects by disconnecting the MAF from the wiring harness and then driving the car. Check engine light may come on cause the MAF's disconnected but the engine should run ok, if the MAF was causing the problem. Any recent service/work done to the engine, or car? Sincerely, Macster.

Hey Macster! No work done this year at all and she was really running great. The problem was instantanteous. I'm wondering if it could maybe be the connector, or the wiring that leads back from MAf to computer. If you get the rpm over 1500 so it won't stall, you can drive the car even at highway speeds as i did when the problem happened, I drove it about 30 miles back to the Indy from where i was. I drove it gingerly, but i noticed that if i gave it a bit of gas while cruising at highway speed, it would "buck" for a second and then pick up. Can it be the computer (hope not!!)

Your car will run without the MAF at idle. Durametric failed or the Mechanic read it wrong I'd assume.

Cory, I'd tend to agree on that. However i changed the MAF because I was there while we read the code fault last Thursday and it clearly said MAF sensor as fault. So now the question is, I've put in a brand new MAF sensor....start the engine, hold the idle with the throttle pedal for a few minutes and then shut it off, attach the Durametric and get the same fault code pointing to the MAF sensor!! Weird!! Pete

Record all the sensor readings from the durametric and post here.

hey mate, My uncle friend had the same problem. The check told him it was the MAF. He changed it and still same problem. The check said again it was the MAF, he bought another one and it worked. sometimes they can be damaged. Replace it, it should work. Try and get it from somewhere else, it could be a damaged batch.. But this scenario happened for real. Good luck mate.

here are the codes P0102 P1123 P0154 P1602 pETE

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P0102 is a generic code for mass air flow circuit, low input. P0154 is a generic code for O2 sensor circuit - no activity detected (bank 2, sensor 1). P1123 is a Porsche code for O2 sensor circuit fault, bank 1. These all point to the MAF, but even with a faulty MAF, I would think the O2 sensors would be sending signals to the engine computer. And while I don't have a code list in front of me, I am pretty sure P1602 is a Porsche code for computer or auxiliary output malfunction. If I were you, I'd first take Cory's advice and see if it idles with the MAF sensor disconnected. And it wouldn't hurt to try another MAF sensor before you go deep on a computer (yuk). Good luck.

NEVER assume that a replacement part isn't itself faulty. Sometimes quality control takes a day off. Try another.

OK gonna try and find a known good sensor through a friend and report back! Pete

If your engine does not idle without the MAF connected, don't plug in another MAF as you may have a short and you will blow the new MAF. What are your sesnor reading as close to idle as possible. O2's, MAF, load, and fuel trim?

I have 1128 and 1130 error codes and my indy says he's pretty sure it is the MAF. He has a machine that basically fills the entire engine system with smoke to locate vacuum leaks, but he said the 2 hours he spends doing that will likely turn out to be a MAF so he thinks I should just replace it. He's only going to charge me parts. I did the gas cap recall and the CEL stayed off...until today. I was hoping that was it.

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P0102 points to MAF (or ECU). P1123 is engine running lean. P0154 also points to MAF or ECU. P1602 logged cause battery disconnected. Any signs of dampness in car cabin? Any possibility of water getting into or on ECU? Check for signs of wetness or moisture wherever ECU is located. Carefully expose it by removing carpet or whatever hides/covers it -- do not remove any cover directly over the Ecu or attempt to unplug it from the harness -- and look very carefully around the unit for any signs of any moisture. You replaced the MAF and that didn't fix the symptom, problem. Did you try disconnecting the MAF and seeing if the symptom remain? The problem can lie with the Ecu or possibly the wiring to/from the MAF. Carefully inspect the MAF plug of the wiring harness to ensure a pin from the old MAF is not broken off in one of the pin holes. There are some electrical tests one can do to help pinpoint the source of this problem. If you want ask and I'll type in the test steps later today when I have my OBD reference handy. Sincerely, Macster.

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Macster, what OBD scanner would you recommend for a Pcar? One that won't break the bank but still be useful?

Hey Macster! I disconnected the MAF wiring harness from the sensor (inside of plug is fine as are the terminals on the new sensor). Then i started her up but still it won't idle at all. Let off the gas and it dies. Inside of the car is bone dry, all carpets, under seats as well. I'll check around the ECU on Saturday. If you have time and don't mind, I would very much appreciate what test steps you feel would be useful to try and further diagnose this! thanks in advance, pete

I chased a MAF related problem for nearly a year. It turned out the first replacement Genuine Bosch/Porsche MAF only lasted about 3 years or 15k miles. The third, an aftermarket replacement did not correct the problem and was later found to be defective from the onset. A fourth aftemarket MAF was tried as well and did not ultimately cure the problem and was found to be defective from new as well. I then went for a new Genuine Bosch/Porsche and it worked immediately, idle was improved, no longer a slight flat spot in the higher rpms, overall driveability improved as well. I didn't think I could have 2 bad replacement MAFs in a row and checked nearly everything else before finally going to the dealer for help. They used the Porsche testing diagnostics and pinpointed the problem immediately. Nice to have friends there.

Hi Nick, the replacement MAF I installed is a genuine Bosch/Porsche part. pete

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I've owned and used an Actron for years now. Actron ok by me. Look through what Actron offers and decide what features you need and what price level you are comfortable with. Be sure the unit you get supports all the standard OBD2 protocols: PWM/VPW, ISO 9141-2 (my 02 Boxster), KWP2000 (my 08 Cayman S and my 03 Turbo), and CAN (my 06 GTO). Features I like: read/erase codes (natch); view OBD2 data in real time; capture OBD2 data in real time (my current unit captures up to 60 seconds worth); check readiness codes; run whatever tests are supported by the car's Ecu. For my Boxster this is just a handful of tests, less than a handful. Of the above features I'd have to say read/erase codes and view OBD sensor and derived data in realtime the two most useful functions and the ones I use most frequently. Sincerely, Macster.

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I may have forgotten to mention it but when you disconnect the MAF it helps to do a code erase. Even if there are no codes this clears out the long term fuel trims and other learned fuel/ignition settings. These may be wrong, way wrong, if the MAF is bad and the engine may not run very well upon restart. If you don't have way to erease codes disconnecting the battery for a while is another way. Follow all safety precautions when disconnecting the battery and before you do so note any radio or other codes so you can reenter these to restore radio function when you reconnect the battery. P0102 points to MAF (or ECU). Do not use ECM ground terminals when measuring input/output voltage signals. This may damage ECM. Use battery or some other ground. Possible faults: MAF faulty; harness or connectors open; sensor circuit shorted; intake air temperature (which is in the MAF). This last item can be checked by when car/engine cold with OBD2 code reader/data viewer looking at OBD sensor data and comparing coolant temperature with air intake temperature. They want to be nearly the same and both should be very close to ambient temperature. One possibility is if either one off and reading high or too low the engine controller will have the wrong temperature upon which it bases how much fuel to inject a cold or a hot engine. 1) Check wiring between MAF and engine control module (ECM) for continuity. Engine at operating temp. Transmission in neutrla or park. A/C off. No load on engine. Disconnect MAF from sensor harness connector plug. Connect special Porsche pin out box 9616 or equivalent to wiring harness plug. Connect digital ohm meter to pin out box pin 17 and ground. Meter should read infinity. Check wiring between MAF sensor and ECM for short to ground. P0154 also points to MAF or ECU. Possible faults: wiring harness; oxygen sensor; ECM final stage faulty. This error code recorded when O2 sensor voltage between 400mV and 600mV for more than 5 seconds without interruption. Test 1) disconnect all 4 sensors. Turn ignition switch to on. Connect digital voltmeter to sleeve pin 3 and 4 of O2 sensor connector 2 ahead of converter. Read approx. 400mV. Connect voltmeter to sleeve pin 3 and ground. Read approx. 720mV. Start engine and run engine at high speed for 3 minutes. (High speed enough to get O2 sensors hot enough to work and the ECM to enter into closed loop mode is what I think is needed.) Connect digital voltmeter to sleeve pin 1 and 2. Read battery voltage. If the measurement according to items 3 and 4 does not show the specified values remove ECM connector and check wires for continuity. If no continuity can be detected repair wiring harness. If continuity ok ECM may need replacing. Test 2) Road test vehicle to bring O2 sensors up to operating temperature. Connect scan tool and read voltage of O2 sensor #2 [this is bank 2, cylinders 4-6] ahead of catalytic converter. Voltage should fluctuate between 100mV and 800mV. O2 sensor ok. [Both the #1 sensors (ahead of the converters) when warm and working proprly should show this voltage fluctuation as this indicates the ECM is as it is supposed to varying the fuel/air mxture between just a little too rich and a little too lean about every second or so at engine idle speed.] Test 3) Remove O2 sensor connector 2 ahead of converter. Connect digital ohmmeter on pin side to pin 1 and 2 of the O2 sensor connector. Read 1.8 to 2.5 ohms at 68 degs. F. (20 Cel.). Connect digital ohmmeter on poin side to pin 1 and the O2 sensor housing. Read infinity. Connect digital ohmmeter on pin side to pin 2 and the O2 sensor housing. Read infinity. P1123 is engine running lean. O2 sensing adaptation range 1 (cyls. 1-3) at lean limit. Fault conditions: fuel pressure too high; fuel injector leaking. Test 1) Remove fuel pressure test cap from fuel injection rail. Connect fuel pressure gage using Baum tool 378 and Porsche adapter 9559 to test port. Actuating fuel pump: Bridging relay - remove fuel pump relay from the central electrical board and bridge terminals 30 and 87 (indentified as 3 and 5 on the relay panel) with a fused shop made test harnesss. The fuel pump should now run and deliver fuel. Values: with engine off 55 +/- 3psi. Engine running: 48 +/- 3psi. Note: The test port seal is not replaceable. The cap must be replaced after removal. Test 2) Remove vacuum line from fuel pressure regulator. Connect vacuum hose to a vacuum gage. Start engine. Read 0.4 to 0.6 bar. Note all of the above for Porsches 1996 to 2004. Just a thought: Any chance of rodent infestation? These creatures don't take long to get into a car that is unused and set up home and in the process gnaw there way around and chew up the wiring harness. I've seen a new Turbo Cab with mice and the damage they can do in nearly no time is tremendous. And car exhibits all kinds of odd engine or other electrical system behavior. Sincerely, Macster.

Macster! Thanks so much for your time in typing out above! Looks like I'll be busy this weekend!! Pete

have you solved? i have the same exact trouble in my mk1 gt3 996... no idle, only when cold can idle, when warm or mid warm no idle at all. changed maf with the exact bosch part no., same behaviour. if i floored it, perfect revving until limiter. no problem with variocam, no apparently loss of power. strange thing, if i look at the board computer, instantaneous fuel consumption is very high, from 20 liters x km to 30. with the old maf i read also 50 liters x km, in normal road use. apparently again these figures are right, car eats a lot of fuel now. already cleaned the injectors. lambda sensors were changed 2000kms ago and should be fine. still wait to attach the official porsche tester, but with generic obd reader no dtc stored in ecu memory.

UP! Pete, are you here? You are my only hope before getting wrecked by OPD...

hello Zampa! Sorry, i haven't been on in a few days! SO after the various bits of advice i decided that the problem must be the ICV (idle control valve) This is located on the left side of the throttle body on the 1999. Very easy to remove. When on the bench, it was apparent that the flap was stuck closed and that explained the complete inability to idle. Once you are above idle, this valve doesn't really serve any purpose and that is why the car runs well but won't idle. (at least in my case!) I filled the inside cavity of the valve body with carb cleaner solution and let it sit for 24 hours, then gently started to work the flap open and closed over and over with small screwdriver. Once i was satisifed that it moved easily and all the carbon had been cleaned out, i tested the selenoid on the valve with 12 vdc and it actuated the valve each time. re-installed onto car and that completely solved my problem! Hope your's is that easy! Pete

Thaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaank you Pete, I will point my Indi in this direction. I have to admit that I have already cleaned the idle valve last summer, and the mechanic told me that it was not in good condition, but it runs when cold so... What about the hesitation when pushing hard the throttle? Was it gone changing the MAF? So, nice that maybe the MAF was still good after 87k kms Thank you all guys Marco

Zampa! The car ran well without any hesitation until the problem with the ICV which gave the problem of not being able to idle at all. If you played with the throttle to keep it running and tried to push it the engine would stumble a bit and then rev ok. When the ICV was cleaned and re-installed the idle was perfect and also the stumbling went away. I suppose there must be some overlap between the ICV and the throttle and that caused my hesitation at the same time as the ICV was not working. Pete