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13

MAP = Manifold absolute pressure and is a sensor to measure vacuum, the computer calculates the engine air flow based on the vacuum, throttle position, and intake air temperature. The computer also measures the barometric pressure using the MAP sensor before the engine cranks, this lets the computer compensate for altitude, or how dense the air is. Typical ...


10

There is no such thing as detectable "reversion" airflow to a MAF. Especially on a non turbocharged car. The MAF has no clue about the direction of flow, only how much energy it takes to keep the wire or film heated. I doubt that the "negative" aspect of your graph is ever seen. Even at idle, you shoud see 2-5 g/s. I wonder why the graph is kg/h... that ...


6

Also, remember that MAF is a reading of the amount of air entering the engine. If you have a backflow issues (high backpressure) or even a timing issue where the valves are not opening and closing at the correct time (slack chains, jumped timing), your MAF sensor readings will reflect this as well. I know this post is late, but any who are looking into this ...


6

The 50 g/s max flow reading that you are getting is far lower than what merely altitude can explain. The chart above shows that at about 5,200 ft above sea level, the density of air is 83% of what it is at sea level (0.062 lb/cu.ft vs. .075 lb/cu.ft). So to account for the altitude, you should multiply your expected mass flow by 0.83. According to the VAG-...


5

Moves.. answer is a good one but you asked about advantages/disadvantages of MAF sensors. Disadvantages are: the sensor sits in the intake and thus restricts airflow. Airflow restrictions translate to performance restriction, particularly with vane style air flow meters. A simple example of this is the comparison between a Subaru STI MAF sensor and a ...


5

Cleaning the MAF won't help here because the fuel trims are negative. A dirty MAF would typically under-read mass air flow and subsequently force a positive fuel trim correction. A few possibilities: oversized fuel injectors If the fuel injectors are pushing through more fuel than what the fuel management is expecting, this would force a negative fuel ...


5

Nice engine you got there! While your issues do sound like a MAF problem (check the MAF readings via OBD!), some turbocharged Volvos are notorious for fuel pressure regulator issues. Basically the regulator diaphragm ruptures and fuel gets into the pressure regulation vacuum hose. Typically this causes poor starting (especially cold) because of an ...


4

I wouldn't if there are no obvious defects in the housing. Sometimes parts stores will only sell items as the complete package. When buying a thermostat from oreilly's auto parts for my forenza the only thing they would sell me is the whole housing unit with the thermostat. When searching on ebay, I found the thermostat without needing to buy the housing as ...


4

Yes. In fact, since you have a MAF sensor, then you likely do already have the expensive equipment required to perform a calibrated test -- it is called an automobile. The only other tool you will need for this test is an OBDii scan tool that allows you to record multiple PIDs in a somewhat simultaneous way. You will need each of the following PIDs, or ...


3

Too lean = too little fuel. I would probably try the fuel injector cleaning (Techron or comparable product) first and see if that clears up the issue. Next try swapping the fuel filter since this is usually a pretty simple/inexpensive repair. (Sorry, can't comment with current reputation)


3

This is the calculation you're looking for. IMAP = RPM * MAP / IAT MAF = (IMAP/120)(VE/100)(ED)*(MM)/(R) Where manifold absolute pressure (MAP) is in kPa, intake air temp (IAT) is in degrees Kelvin, R is 8.314 J/°K/mole and the average molecular mass of air (MM) is 28.97 g/mole. Note that, in the above formula, the volumetric efficiency of the (4-cycle!) ...


3

In the turbo applications I am familiar with, both a wire or film (better) type MAF is used, in conjunction with a MAP, IAT, ECT, etc. Specifically on turbosupercharged Subarus, there's knowledge to be gained by also knowing intake pressure. Ultimately, you are trying to reach the best AFR. Things change a bit when supercharging, whether mechanical or ...


2

I just had these exact symptoms with a 2002 Vauxhall Astra. As well as the Crankshaft Sensor error (and the garage confirmed it had previously thrown out an O2 sensor error). Mine was the EGR valve, with fuels that use a lot of additives (here in the UK that's 'supermarket fuel') the valve quickly becomes caked in carbon. The EGR (exhaust gas ...


2

Checking a list of TSBs for this set of codes, this looks like a promising candidate: 01-028/04 MAZDA SPECIAL PROGRAM (MSP05) - 2004 MAZDA3 - O2 SENSOR DTC ERROR, P2195 / P2196 From what you describe, a problematic O2 sensor could easily lead to the idling, sputtering and smells that you describe. If the sensor is stuck reading full lean, it's highly ...


2

The fault code P0171 descriptor is Bank 1 running lean. The fault code P0174 descriptor is Bank 2 running lean. This means that your engine has too much air or not enough fuel for proper ignition. This can be a faulty MAF sensor as it is common to both banks. It can also mean that you have an air leak between the MAF sensor and the throttle body, a faulty ...


2

When discussing the Throttle Position Sensor You understand it's function electrically on a 5v reference. If you were to take the sensor off and look at the side that goes against the throttle body then you would notice the coil. The inductive loop works as follows. When the butterfly of the throttle body opens (up until wide open throttle) voltage ...


2

Do you have a source for that formula? Is it possible that you are reading Calculated engine load value, which would indeed be zero when you are in neutral? Range: 0 to 100 Units: % Formula: A*100/255 I did find this page which defines it as: Calculated Load Value -- Indicates a percentage of peak available torque. Reaches 100% at wide open throttle at ...


2

I think you misunderstand the purpose of the Mass Air Flow (MAF) sensor (and whoever wrote what you read doesn't understand, as well). The purpose of the MAF is to read the amount of incoming air. As the incoming air flows over the heated sensor, it cools the sensor which regulates the amount of electricity which can flow through it. It is in no way ...


2

I have a 2005 Hyundai Elantra, and I was getting OBDII error codes: P2626 Hyundai - HO2S Pumping Current Trim Circuit/Open Bank 1 Sensor 1 .. and later, I also got P2196 Hyundai - HO2S Signal Stuck Rich Bank 1 Sensor 1 My car was sputtering, somewhat intermittently. It would intermittently lose power rather suddenly while accelerating. The egine was also ...


2

Milan, I recommend that you purchase a paper Chilton's or Haynes repair manual for your car. They cost around $30 at your local autoparts store. Many manufacturers have provided a 'secret' code that you can use to turn your check engine light into a blinking code reader. The instructions for that tend to be written in the repair manual (not all ...


2

Yes, provided the following conditions are met: the units for the values MAF and fuel flow values are consistent. if you're using OBD-II parameters the values are usually in different units. In fact, fuel flow is usually volumetric (L/hr) and not mass flow like the reading from the MAF so you would have to correct for that by injector flow rate, I'm ...


2

The MAF should be fine Have a look at this datasheet for the HFM5 series Bosch MAF. It is for a 5-pin MAF (it also measures intake air temperatures) so it's not exactly what you're after, but remains relevant because the fundamental MAF design is more than likely identical: Nominal supply voltage is 14 V Supply-voltage range is 8 - 17 V Output ...


2

Well, it turns out that the 1996 Ford E350 doesn't have a Mass Air Flow sensor - hence the trouble finding it :-) Instead, it has a MAP (Manifold Absolute Pressure) sensor, which looks like this: And can be found here: Thanks for your help with this!


2

It should be on or near the air cleaner assembly. It looks like a square thing with a 60 pin connector on it http://www.ford-trucks.com/how-tos/a/ford-f150-f250-how-to-clean-a-faulty-mass-airflow-sensor-361730


2

Open and closed loop are control algorithms usually coded in the ecu - but to solve your problems apply the tests and look at the results, the code and meaning you show suggest a replacement sensor is required. The trim values can usually be used, if they are editable, to "fine tune" the sensor in the application - perhaps due to parameters such as pipe ...


2

The engine runs in "open loop" when first started, before the oxygen sensors come up to operating temperature. It basically means the fuel is being metered with MAP/MAF as the primary input. Once warmed up, fuel is metered by an active feedback loop with the O2 sensor, known as closed-loop operation.


2

The MAF supplies air flow and temperature data to the car's computer, a failing MAF sensor can definitely produce surging at idle which is what it sounds like you have. You might also get hesitation or jerky acceleration, and find it's hard to start. A dirty one can also cause the same issues, so it makes sense to try cleaning it before replacing. There's ...


2

So far so good with the MAF cleaning, haven't had the codes pop up for about 850mi post cleaning and the MAF housing's interior and the laminar air screen were definitely dirty. I'm assuming the actual sensor itself was likewise dirtied up though I couldn't inspect any real dirt on its parts. I gave the part a good squirt down with CRC 05110 Mass Air Flow ...


2

I can imagine this could be a bad MAF - giving a valid signal (so the ECU does not throw a DTC/CEL) yet corresponding to a wrong air amount. Does this happen no matter what the engine temperature is or eg. when cold only? Anyway, you should be able to isolate the MAF by simply unplugging it - you surely will receive a CEL but for the mixture preparation, ...


2

Check for disconnected vacuum lines also - there's one that comes to mind which runs from the throttle body to the rear of the engine compartment on the passenger side. Easily knocked off its fixing, and can cause idling/stalling issues.


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