It would of some value I think to post the codes... |  |  |
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| Replace MAF Mass Airflow Sensor? catalogguy - 9 years ago |
So after getting my brakes done today (and the headlight plug adjusted), I have a couple new issues to tackle.
First is I am told that a couple of my codes (I've had codes for over a decade) is from a failing mass airflow sensor. I recall years back when we first started having problems with these things. I think I have an extra one in a box somewhere, although I cannot recall whether if it is new, and if not whether it even came out of my car. And since then I have had the ECU replaced, so maybe an old mass will not be compatible with the ECU. There is some info on Pelican about getting the right MAF; it seems to require a little diligence. I am quoted 750 for the job, which includes the part at about 500 including tax. I thought replacing the MAF took just a few minutes, but maybe I am confusing it with something. At any rate, has there been any success cleaning the MAF? I see Pelican sells some CRC MAF cleaning spray. Otherwise, is replacement an easy job to tackle?
Also, my ongoing CEL comes from codes that indicate a bad O2 sensor (problem appeared coincident with installation of headers). It is just one sensor, after the cat converter. I had it replaced in the past with a sensor I bought online for about $60, and the replacement did not help. Many over the years have looked at the problem and there has been no progress, but now the mechanic I am working with has recommended trying to replace it again. I am quoted $400 which does not seem all that bad, but if I can save a few bucks, I'd be inclined to give it a go. How hard is it to do? I think it screws in like a spark plug, so my bigger concern, if that much is correct, is the process of attaching the lead. I ordered the 101 projects book tonight, and I hope that fills the vacuum a bit.
Thanks everyone for always being a supportive, helpful, and friendly group year after year!
First is I am told that a couple of my codes (I've had codes for over a decade) is from a failing mass airflow sensor. I recall years back when we first started having problems with these things. I think I have an extra one in a box somewhere, although I cannot recall whether if it is new, and if not whether it even came out of my car. And since then I have had the ECU replaced, so maybe an old mass will not be compatible with the ECU. There is some info on Pelican about getting the right MAF; it seems to require a little diligence. I am quoted 750 for the job, which includes the part at about 500 including tax. I thought replacing the MAF took just a few minutes, but maybe I am confusing it with something. At any rate, has there been any success cleaning the MAF? I see Pelican sells some CRC MAF cleaning spray. Otherwise, is replacement an easy job to tackle?
Also, my ongoing CEL comes from codes that indicate a bad O2 sensor (problem appeared coincident with installation of headers). It is just one sensor, after the cat converter. I had it replaced in the past with a sensor I bought online for about $60, and the replacement did not help. Many over the years have looked at the problem and there has been no progress, but now the mechanic I am working with has recommended trying to replace it again. I am quoted $400 which does not seem all that bad, but if I can save a few bucks, I'd be inclined to give it a go. How hard is it to do? I think it screws in like a spark plug, so my bigger concern, if that much is correct, is the process of attaching the lead. I ordered the 101 projects book tonight, and I hope that fills the vacuum a bit.
Thanks everyone for always being a supportive, helpful, and friendly group year after year!
| It would of some value I think to post the codes... MarcW - 9 years ago |
Generally the MAF is pretty reliable. Generally the problem lies elsewhere. For instance I missed an oil filler tube cap leak and replaced a perfectly good MAF. Thankfully after the replacement MAF failed with over 100K miles of use I had the original one still in its box to put back in.
The only incompatibility I'm aware of is in older/earlier MY's the old MAF is not available. A newer MAF can be used but this requires the ECU flash be updated.
The MAF only benefits from cleaning if it is dirty. It can get dirty one of several ways. The most common way is an aftermarket air filter with oil that coats the MAF with oil. Another way is if the stock air filter or air filter box is compromise and allowing unfiltered air in.
The Boxster has had its MAF cleaned just twice. Once at just under 80K miles when trouble-shooting what proved to be a bad AOS. The next time when what proved to be an air leak past a bad oil filler tube cap. I do not recall the miles. In both cases the MAF was not dirty. (In the first case the throttle body was dirty and the engine seems to get some benefit from cleaning this, but the benefit was short-lived.)
The 996 has never has its MAF cleaned in the 114K miles I have put on the car out of 124K miles total on the car. I doubt the MAF was cleaned in the 10K miles the original owner put on the car.
However, you can clean the MAF if you want, if it makes you feel better. Clean it over clean white paper towels with the right cleaner. Let the fluid fall on the towels. If you see dirt then the MAF was dirty and the cleaning could help. But you need to figure out how the dirt got on the MAF.
Handle the MAF with care. Static discharge into its connector and you ruin it. Static discharge into the connector it connects to and you can ruin the DME. Expensive. Drop the MAF and you ruin it.
Replacing the MAF is an easy job. You need the right style (has a hole in its center to clear the 'pip' in the Torx screw head socket) and the right size Torq tool bit. Disconnect the MAF at the wiring harness. Unscrew the hold down screw. Pull out the MAF. Install the new MAF. It is keyed so it can only be inserted the right way. Screw in the hold down screw. Connect the MAF at the harness connector., Be sure the connector latches. Ideally you should clear the error codes which resets the learned values so the values are replaced with the values derived from the new MAF but this will happen anyway as the engine runs. If the old MAF was terribly bad though the engine may not run very good from the outset and this can lead you to believe the new MAF was not needed.
I need to see the O2 sensor error codes and converter codes before I can speak much about these.
O2 sensors are not hard to replace. My experience is the biggest hurdle is getting the connector to unlatch. Do this first before you unscrew the sensor. Then the sensor just unscrews. It should not be that tight but it can be stuck by its threads.
I hesitate to tell you can use some penetrating oil as if there is any reside this can affect the new sensor.
When you install the new sensor do not touch its tip. Do not use any thread lube/sealant. Do not use any cleaner to clean the old sensor or the new one. The sensor must have outside air around its inner tip to function properly and any cleaner can get where it is *not* supposed to and damage (ruin) the sensor. LIke the MAF sensors can be damaged by a static discharge at the tip or at the connector end. Do not use a volt/ohm meter to measure resistance of the sensor. In short the old sensor is removed, and the new sensor screwed in, tightened and connected.
Also like MAF's sensors are generally long-lived. Before you throw more sensors at the symptoms (error codes) we need to know the codes. All the new sensors in the world will not improve things if the problem lies, for instance, with the exhaust system.
The only incompatibility I'm aware of is in older/earlier MY's the old MAF is not available. A newer MAF can be used but this requires the ECU flash be updated.
The MAF only benefits from cleaning if it is dirty. It can get dirty one of several ways. The most common way is an aftermarket air filter with oil that coats the MAF with oil. Another way is if the stock air filter or air filter box is compromise and allowing unfiltered air in.
The Boxster has had its MAF cleaned just twice. Once at just under 80K miles when trouble-shooting what proved to be a bad AOS. The next time when what proved to be an air leak past a bad oil filler tube cap. I do not recall the miles. In both cases the MAF was not dirty. (In the first case the throttle body was dirty and the engine seems to get some benefit from cleaning this, but the benefit was short-lived.)
The 996 has never has its MAF cleaned in the 114K miles I have put on the car out of 124K miles total on the car. I doubt the MAF was cleaned in the 10K miles the original owner put on the car.
However, you can clean the MAF if you want, if it makes you feel better. Clean it over clean white paper towels with the right cleaner. Let the fluid fall on the towels. If you see dirt then the MAF was dirty and the cleaning could help. But you need to figure out how the dirt got on the MAF.
Handle the MAF with care. Static discharge into its connector and you ruin it. Static discharge into the connector it connects to and you can ruin the DME. Expensive. Drop the MAF and you ruin it.
Replacing the MAF is an easy job. You need the right style (has a hole in its center to clear the 'pip' in the Torx screw head socket) and the right size Torq tool bit. Disconnect the MAF at the wiring harness. Unscrew the hold down screw. Pull out the MAF. Install the new MAF. It is keyed so it can only be inserted the right way. Screw in the hold down screw. Connect the MAF at the harness connector., Be sure the connector latches. Ideally you should clear the error codes which resets the learned values so the values are replaced with the values derived from the new MAF but this will happen anyway as the engine runs. If the old MAF was terribly bad though the engine may not run very good from the outset and this can lead you to believe the new MAF was not needed.
I need to see the O2 sensor error codes and converter codes before I can speak much about these.
O2 sensors are not hard to replace. My experience is the biggest hurdle is getting the connector to unlatch. Do this first before you unscrew the sensor. Then the sensor just unscrews. It should not be that tight but it can be stuck by its threads.
I hesitate to tell you can use some penetrating oil as if there is any reside this can affect the new sensor.
When you install the new sensor do not touch its tip. Do not use any thread lube/sealant. Do not use any cleaner to clean the old sensor or the new one. The sensor must have outside air around its inner tip to function properly and any cleaner can get where it is *not* supposed to and damage (ruin) the sensor. LIke the MAF sensors can be damaged by a static discharge at the tip or at the connector end. Do not use a volt/ohm meter to measure resistance of the sensor. In short the old sensor is removed, and the new sensor screwed in, tightened and connected.
Also like MAF's sensors are generally long-lived. Before you throw more sensors at the symptoms (error codes) we need to know the codes. All the new sensors in the world will not improve things if the problem lies, for instance, with the exhaust system.
| P codes: catalogguy - 9 years ago |
| Re: P codes: MarcW - 9 years ago |
P1117 - O2 sensor heating after TWC - bank 1. Signal implausible.
This does suggest a problem with the sensor. The error is related to the heater circuit.
Some things you can do: Visually check sensor for corrosion.
Check sensor heating: Disconnect sensor connection and check resistance between pins 1 and 2. Read 9 to 10 ohms at 20C. Check sensor: Check resistance between pin 1 and the sensor housing. Check resistance between pin 1 and pin 3. Read infinite ohms.
P0140 - O2 sensor after TWC - Bank 1. Open circuit in signal wire or ground wire of sensor or the sensor heater is faulty.
P0136 - O2 sensor after TWC - Bank 1. Signal implausible. Short circuit to ground in signal wire. Intercore short circuit.
There are some diagnostics that involve checking the various circuits/wiring between the DME and the sensor connector and the sensor connector itself. I can make a copy of these tests in a PDF format and send it to you if you want.
Or, you can replace the sensor indicated by the error codes. I note all 3 error codes point to the same sensor. Thus I'd be inclined to the sensor indicated along with its counterpart on the other bank. I like to replace sensors in pairs to avoid introducing bank fueling differences due to the age differences of the sensors.
While I'm not a big fan of throwing parts at symptoms sometimes this is a quick way of highlighting where the problem might lie. (Another is swapping a suspected bad sensor with its twin from the other bank. This is a bit risky if one is not careful he can damage a perfectly good sensor in this swapping. This swapping then is intended to see if the behaviour/error codes follow the sensor or remain.)
I'm always reluctant to start messing with electrical circuits. In the case of the Porsche it requires some specialized break out box hardware, instructions for how to use this to test various circuits for your particular car, and in this particular case getting up close and personal with a volt/ohm meter with the DME which requires you gain access to the DME and disconnect it from the harness connector. If one is not very careful he can static discharge into the DME and ruin it. He can damage a connector, break a pin, or bend one.
By throwing new parts, O2 sensors in this case, and parts that one assumes work ok out of the box, if the symptoms persist then that is a sign one must delve further into some cause a bit removed from the sensor itself.
Now to the next pair of codes:
P1128 - Oxygen sensing adaptation, idle range, bank 1.
P1130 - Oxygen sensing adaptation, idle range, bank 2.
My references list "incorrect signal from MAF sensor" at the top of the list of possible fault causes.
Other possible fault causes: fuel pressure too high. Leaking fuel injector. EVAP canister purge valve open.
Since the error is present from both banks the fault this suggests the fault is a common one which points to: MAF, too high a fuel pressure, or EVAP canister purge valve open. While a leaking injector could account for this error on one bank the odds of leaking injectors on both banks are too long.
There is the shade tree mechanic's "test" of disconnecting the MAF at the wiring harness, and clearing the error codes and then just driving the car around to see if the MAF related error codes return.
There is some question in my mind about dealing with suspected O2 sensor problems and a suspected MAF problem simultaneously. I do not know how problems with the MAF might manifest themselves as collateral errors at the sensors. However a bad heating circuit and some of the other sensor related errors strongly point to a failure at the sensor (or with the circuit between the DME and the sensor) and not just something arising from sensor readings brought about by a failing MAF.
This does suggest a problem with the sensor. The error is related to the heater circuit.
Some things you can do: Visually check sensor for corrosion.
Check sensor heating: Disconnect sensor connection and check resistance between pins 1 and 2. Read 9 to 10 ohms at 20C. Check sensor: Check resistance between pin 1 and the sensor housing. Check resistance between pin 1 and pin 3. Read infinite ohms.
P0140 - O2 sensor after TWC - Bank 1. Open circuit in signal wire or ground wire of sensor or the sensor heater is faulty.
P0136 - O2 sensor after TWC - Bank 1. Signal implausible. Short circuit to ground in signal wire. Intercore short circuit.
There are some diagnostics that involve checking the various circuits/wiring between the DME and the sensor connector and the sensor connector itself. I can make a copy of these tests in a PDF format and send it to you if you want.
Or, you can replace the sensor indicated by the error codes. I note all 3 error codes point to the same sensor. Thus I'd be inclined to the sensor indicated along with its counterpart on the other bank. I like to replace sensors in pairs to avoid introducing bank fueling differences due to the age differences of the sensors.
While I'm not a big fan of throwing parts at symptoms sometimes this is a quick way of highlighting where the problem might lie. (Another is swapping a suspected bad sensor with its twin from the other bank. This is a bit risky if one is not careful he can damage a perfectly good sensor in this swapping. This swapping then is intended to see if the behaviour/error codes follow the sensor or remain.)
I'm always reluctant to start messing with electrical circuits. In the case of the Porsche it requires some specialized break out box hardware, instructions for how to use this to test various circuits for your particular car, and in this particular case getting up close and personal with a volt/ohm meter with the DME which requires you gain access to the DME and disconnect it from the harness connector. If one is not very careful he can static discharge into the DME and ruin it. He can damage a connector, break a pin, or bend one.
By throwing new parts, O2 sensors in this case, and parts that one assumes work ok out of the box, if the symptoms persist then that is a sign one must delve further into some cause a bit removed from the sensor itself.
Now to the next pair of codes:
P1128 - Oxygen sensing adaptation, idle range, bank 1.
P1130 - Oxygen sensing adaptation, idle range, bank 2.
My references list "incorrect signal from MAF sensor" at the top of the list of possible fault causes.
Other possible fault causes: fuel pressure too high. Leaking fuel injector. EVAP canister purge valve open.
Since the error is present from both banks the fault this suggests the fault is a common one which points to: MAF, too high a fuel pressure, or EVAP canister purge valve open. While a leaking injector could account for this error on one bank the odds of leaking injectors on both banks are too long.
There is the shade tree mechanic's "test" of disconnecting the MAF at the wiring harness, and clearing the error codes and then just driving the car around to see if the MAF related error codes return.
There is some question in my mind about dealing with suspected O2 sensor problems and a suspected MAF problem simultaneously. I do not know how problems with the MAF might manifest themselves as collateral errors at the sensors. However a bad heating circuit and some of the other sensor related errors strongly point to a failure at the sensor (or with the circuit between the DME and the sensor) and not just something arising from sensor readings brought about by a failing MAF.
| Durametric screens catalogguy - 9 years ago |
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