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Old 12-22-2019, 12:44 PM
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Mass Airflow Sensor error code

On my 2003 4.4 M62 I just replaced the alternator, and in the process, fixe the notorious valley pan coolant leak, replaced the leaky valve cover gaskets, and installed a new water pump. I had the car in the garage for a few weeks ordering parts as I got deeper and deeper into this. Amazing how the valve cover gaskets get so hard and brittle. Absolutely no seal.

With all that done, I put it all back together and drove it for a short test, 4 miles. Then took it to the airport for a 50 mile run. All good. It sat for three days. Then on the way back from the airport, it mysteriously started to feel like no power. The throttle would not respond, then would race, then cut out. The engine never stalled, but the throttle was very uneven. I thought it was possibly the fuel pump since it felt like fuel was being turned on and off.

I thought bad fuel? So I stopped and bought some HEET and put that in the tank thinking maybe moisture from sitting so long and the cold weather here in Colorado this time of year.

I sat for a day. Still same problem. Starts right up, but throttle very bizarre. Seems to cut out and then race, then runs ok, then very erratic.

I checked the full pressure today and 48 # while running so looked good.

But when I put my scanner on it after clearing a bunch of misfire error codes, I got this "73 Signal, hot film air-mass flow sensor". There are no other MAS error codes and the MAS sensor seems to be working correctly. I cleaned the sensor with MAS spray and tried again. Still same problem.

Could it be the MAS that is now bad? After having it all apart I was thinking vacuum leak, but everything ran fine and I was very careful with gaskets and torqueing everything down correctly.

I have a call in to customer support at iCarsoft the scanner maker but thought to put this out to get some other ideas.
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Old 12-22-2019, 12:50 PM
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A quick extra test is with it running at an idle tap on the MAF next to the sensor film. If you get a stumble your MAF is toasted.

Ditch medicine isn't just for people anymore

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Old 12-22-2019, 12:51 PM
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Use a screwdriver handle

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Old 12-23-2019, 11:30 AM
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Tried the simple test...no stumble. Starting to think the 43 message is intermittent signal based on someone else’s post using the same iCarsoft scanner. Waiting to hear from support but may try a drive test with the scanner attached. It may still be the MAS or a bad connection.

Thanks
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Old 01-18-2020, 11:45 AM
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Replaced the MAS with new Bosch, that was the problem.
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Old 01-18-2020, 12:13 PM
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I've noticed that some OE parts like the MAF have a T shaped hot film block and it works fine for a few months to a year then dies. This kind is the multi use one and works on the Land Rover. (Don't ask how I know...)


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