Thread: mass airflow sensor

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what exactly happens to a motor when the mass airflow sensor goes bad?

usally bad or no idle,no power and the check engine light comes on.

Ok here's what I'm having, I'm thinking it's the the airflow sensor. I have a 91 volvo turbo. no check engine light as of yet, but when I'm on the gas and the rpm's gets to 5000 it's almost like the rev limiter kicks on and it it stops. the engine surges and shakes and the turbo boost gauge goes crazy. But the reason I'm thinking this is the airflow sensor is because it's dependent on the temp outside. the warmer it gets the sooner in the rpm band it'll do it

I'm not sure about Volvos thought you might be talking about a
firebird. Check the air duct between airflow sensor and the intake'
sometimes it has a crack and it can cause strange problems.

http://www.misterfixit.com/volvo740.htm

Volvo's are a pain to diagnose, But i would check several things, first is fuel preasure, make sure ya have proper preasure at the injectors /or fuel rail, most old Volvos had 2 fuel pumps,one in the tank called a supply pump,and one on the frame rail called the main pump, have seen more than a few misdiagnosed
because of the supply pump ( not all are aware they have 2 pumps), also check all the air intake boots & clamps to the throttle body,turbo, & intercooler, check all the engine vacume hoses and make sure something hasn't come disconnected, maybe a wastegate problem causing overboost??? hope some of this helps....

replaced most of the vaccum lines they were kinda deteriorated. I was thinking the same thing with the wastegate. I did come in from testing the maf sensor and it was reading 44.8 kohms manual says it should read 2.5-4.0 ohms. So it's bad. Sucks too cause a new one is 168 bucks from autozone with a 60 core. I guess these things can be rebuilt. My first volvo, hell my first foreign car. I knew mustangs has MAF sensors so I thought I'd put thta in there. Sucks about the fuel pressure I can't find a schrader valve anywhere on it. I do know it's supposed to read a constant 42 psi at the fuel rail. I think I might just take this in to have someone look at it.

Yeah the fuel preasure is a pain Too. ya need a special banjo bolt adapter....

banjo bolt adapter? wtf?

The fuellines are held to the injectors with a banjo fitting & bolt, so ya gotta have a special fitting & bolt to installl to hook your gauge to. Wish I had a pic,but ......

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firebird45331, sometimes it don't hurt to check for codes even though the light is not on. could save you a lot of trouble. if there is no codes that's suppose to eliminate a lot of things.



Fuel Codes
Locate the diagnostic unit behind left strut tower and remove its cover.(see image) Connect selector cable to socket #2,which tests the fuel codes. Turn the ignition switch to the ON position(engine not running). Enter the diagnostic mode by pressing the push button on the diagnostic unit for at least 1 second, but not more than 3 seconds. The red LED light will start to flash,count the number of flashes in 3 flash intervals. The flashes will be seperated by 3 second intervals.Make note of all codes. If no codes are stored,the LED will flash 1-1-1,which means the fuel system is operating correctly.

Ignition Codes
To access the ignition codes,follow the above procedure,but with the selector cable connected to the #6 socket on the diagnostic unit.
NOTE:Turbocharged models may have seperate codes for the turbo system and are accessse by hooking the selector cable to the #5 socket.

Diagnostic Codes
Volvo
89-93 models
1-1-1 No faults.
1-1-2 ECU.
1-1-3 Fuel injectors.
1-1-3 Heated Oxygen sensor-max enrichment sensed (94-up).
1-1-5 Injector #1.
1-2-1 Mass airflow sensor.
1-2-2 Air temp sensor signal.
1-2-3 Coolant temp sensor signal.
1-2-5 Injector #2.
1-3-1 Ignition system RPM signal.
1-3-2 Battery voltage.
1-3-3 Throttle switch signal (idle).
1-3-5 Injector #3.
1-4-2 ECU faulty.
1-4-3 Knock Sensor signal missing or defective.
1-4-4 Fuel system load signal(missing or defective).
1-4-5 Injector #4.
1-5-3 Rear heated oxygen sensor signal.
1-5-4 EGR system-leakage or excessive flow.
1-5-5 Injector #5.
2-1-2 Oxygen sensor signal(front sensor on 94 and later models).
2-1-3 Throttle switch signal.
2-1-4 Ignition RPM signal erratic.
2-2-1 Heated Oxygen Sensor(Rich mixture/part throttle).
2-2-2 Main relay.
2-2-3 Idle valve signal.
2-2-4 Coolant temp sensor signal.
2-2-5 A/C pressure sensor signal.
2-3-1 Lambdfa adjustment.
2-3-1 Heated Oxygen sesnor(lean mixture/part throttle) 94-up.
2-3-2 Lamda adjustment.
2-3-2 Adaptive heated O2 sensor control (94-up).
2-3-3 Idle valve-closing signal.
2-3-4 Throttle switch signal missing.
2-4-1 EGR malfunction.
2-4-5 Idle air control valve-closing signal.
3-1-1 Speedometer signal.
3-1-4 Camshaft position signal missing or defective.
3-1-5 EVAP emission control system.
3-2-1 Cold start valve-signal missing.
3-2-2 Airflow meter hot wire.
3-2-4 Camshaft position siganl erratic.
3-2-5 ECU memory failure.
3-3-5 TCM request for MIL.
4-1-1 Throttle switch signal faulty or missing.
4-1-3 EGR temp sensor signal incorrect or missing.
4-1-4 Turbo boost regulation.
4-1-6 Turbo boost reduction from TCM.
4-2-5 Temp warning level #1.
4-3-1 EGR temp sensor faulty or missing.
4-3-2 High temp warning inside ECU.
4-3-3 No rear knock sensor signal.
4-3-5 Front heated oxygen sensor - slow response.
4-3-6 Rear heated oxygen sensor compensation.
4-4-3 Catalytic converter efficiency.
4-4-4 Acceleration sensor signal.
4-5-1 Misfire - #1 cylinder.
4-5-2 Misfire - #2 cylinder.
4-5-3 Misfire - #3 cylinder.
4-5-4 Misfire - #4 cylinder.
4-5-5 Misfire - #5 cylinder.
5-1-1 Adaptive oxygen sensor control-lean mixture at idle.
5-1-2 Oxygen integrator at max lean running limit.
5-1-3 High temp warning inside ECU.
5-1-4 Engine cooling fan-low speed signal faulty.
5-2-1 Oxygen sensor preheating-front.
5-2-2 Oxygen sensor preheating- rear.
5-3-1 Power stage-group A.
5-3-2 Power stage-group B.
5-3-3 Power stage- group C.
5-3-4 Power stage- group C.
5-3-5 TC control valve signal.
5-4-1 EVAP valve signal.
5-4-2 Misfire - more than one cylinder.
5-4-3 Misfire - at least one cylinder.
5-4-4 Misfire - more than one cylinder/catalytic converter damage.
5-4-5 Misfire - at least one cylinder/catalytic converter damage.
5-5-1 Misfire - #1 cylinder/catalytic converter damage.
5-5-2 Misfire - #2 cylinder/catalytic converter damage.
5-5-3 Misfire - #3 cylinder/catalytic converter damage.
5-5-4 Misfire - #4 cylinder/catalytic converter damage.
5-5-5 Misfire - #5 cylinder/catalytic converter damage.

I checked for codes last night only codes I was getting was 1-2-1 (which I did while checking the impedance) and 2-1-2 I don't remember the second one exactly, but I knew it was concerning the automatic adjustment oxygen sensor. It's kinda nifty how volvo has it's onboard diagnostics like that.

Originally posted by firebird45331
I checked for codes last night only codes I was getting was 1-2-1 (which I did while checking the impedance) and 2-1-2 I don't remember the second one exactly, but I knew it was concerning the automatic adjustment oxygen sensor. It's kinda nifty how volvo has it's onboard diagnostics like that.

most all cars has a onboard diagnostics like that up until 1996 when they went to the (OBD 2). now you need a scaner.

all the cars I ever owned just used a gm key to jump jumpers or activate the obd with the ignition switch. I never had a car that had the little terminal and jumpers like that for all the systems that allowed you to do three levels of diagnostics.