maf sensors
 -
RSS

Recent Posts

2.4 quad 4 motor job
gmc sierra
jiffy lube problems
chrsyler dip stick problems
maf sensors

Categories

2007 chevy cobalt
battery
jiffy
quad 4 motors
powered by

My Blog

maf sensors

An engine with a bad MAF sensor may be hard to start or stall after starting. It may hesitate under load, surge, idle rough or run excessively rich or lean. The engine may 
also hiccup when the throttle suddenly changes position. 
If you suspect a MAF sensor problem, scan for any fault codes. A MAF problem should (but does not always) set a fault code. Codes that may indicate a problem with 
the sensor include: GM: Code 33 (too high frequency) and Code 34 (too low frequency) on engines with multiport fuel injection only, and Code 36 on 5.0L and 5.7L engines that use the Bosch hot-wire MAF, if the burn-off cycle after shut-down fails to occur. 

Of course, don’t overlook the basics, such as low engine compression, low vacuum, low fuel pressure, leaky or dirty injectors, ignition misfire, excessive backpressure (plugged converter), etc., since problems in any of these areas can produce similar driveability symptoms. 

MAF sensors can be tested either on or off the vehicle in a variety of ways. You can use a MAF Sensor Tester and 
tachometer to check the sensor’s response. If testing on the vehicle, unplug the wiring harness connector from the sensor and connect the tester and tachometer. Start the engine and watch the readings. They should change as the throttle is opened and closed. No change would indicate a bad sensor. The same hookup can be used to test the MAF sensor off the 
vehicle. When you blow through the sensor, the readings should change if the sensor is detecting the change in air flow.Another check is to read the sensor’s voltage or frequency output on the vehicle. With Bosch hot-wire MAF sensors, the output voltage can be read directly with a digital 
voltmeter by backprobing the brown-andwhite output wire to terminal B6 on the PCM. The voltage reading should be around 2.5 volts. If out of range, or if the sensor’s voltage output fails to increase when the throttle is opened with the engine running, the sensor may be defective. Check the orange and black feed wire for 12 volts, and the black wire for a good ground. Power to the MAF sensor is provided through a pair of relays (one for power, one for the burn-off cleaning cycle), so check the relays too, if the MAF sensor appears to be dead or sluggish. If the sensor works but is slow to respond to changes in air flow, the problem may be a contaminated sensing element caused by a failure in the self-cleaning circuit or relay. With GM Delco MAF sensors, attach a digital voltmeter to the appropriate MAF sensor output terminal. With the engine idling, the sensor should output a steady 2.5 volts. Tap lightly on the sensor and note the meter reading. A good sensor should show no change. If the meter reading jumps and/or the engine momentarily misfires, the sensor is bad and needs to be replaced. You can also check for heat-related problems by heating the sensor with a hair dryer and repeating the test. This same test can also be done using a meter that reads frequency. The older AC Delco MAF sensors (like a 2.8L V6) should show a steady reading of 32 Hz at idle to about 75 Hz at 3,500 rpm. The later model units (like those on a 3800 V6 with the Hitachi MAF sensor) should read about 2.9 kHz at idle and 5.0 kHz at 3,500 rpm. If tapping on the MAF sensor produces a sudden change in the frequency signal, it’s time for a new sensor. 

On GM hot-film MAFs, you can also use a scan tool to read the sensor’s output in “grams per second” (gps), which corresponds to frequency. The reading should go from 4 to 8 gps at idle up to 100 to 240 gps at wide-open throttle. Like throttle position sensors, there should be smooth linear transition in sensor output as engine speed and load change. If the readings jump all over the place, the computer won’t be able to deliver the right air/fuel mixture and driveability and emissions will suffer. So you should also check the ensor’soutput at various speeds to see that its output hanges appropriately. Another way to observe the sensor’s 
output is to look at its waveform on an oscilloscope. The waveform should be square and show a gradual increase in frequency as engine speed and load increase. Any skips 
or sudden jumps or excessive noise in the pattern would tell you the sensor needs to be replaced. Yet another way to check the MAF sensor is to see what effect it has on injector timing. Using an oscilloscope or multimeter that reads milliseconds, connect the test probe to any injector ground terminal (one injector terminal is the supply voltage and the other is the ground circuit to the computer that controls injector timing). Then look at the duration of the injector pulses at idle (or while cranking the engine if the engine won’t 
start). Injector timing varies depending on the application, but if the mass air flow sensor is not producing a signal, injector timing will be about four times longer than normal (possibly making the fuel mixture too rich to start). You can also use millisecond readings to confirm fuel enrichment when the throttle is opened during acceleration, fuel leaning during light load cruising and injector shut-down during deceleration. Under light load cruise, for example, you should see about 2.5 to 2.8 Ms duration.

9 Comments to maf sensors:

Comments RSS
one day courses on Friday, January 16, 2015 4:28 PM
I find myself firmly over it as well as appreciate finding out a lot more on this subject.
Reply to comment


Tonya K. Ibanez on Thursday, September 15, 2016 7:37 AM
Car techniques like these are useful for brand new or current car owners. Popular topics like no credit check car loans, best mid-size cars of the year, most expensive cars of the year, top cars of the year, etc are helpful to anyone looking for useful information online. Thanks a lot for this!
Reply to comment


rush essay on Wednesday, June 28, 2017 4:09 AM
Best engine is the good reflect of the car performance. If the engine is running late and makes the bad performance it affects the efficiency of the petrol and power supply. The MAF sensor is the important current baring circuit which helps to start an engine. The good sensor supply energy in a given time.
Reply to comment


essay paper service on Thursday, January 25, 2018 6:39 AM
We have a plan for making a trip in front to the summer in the next year.Could you please recommend some remarkable place for spending the summer vacation.
Reply to comment


perfect replica watches on Saturday, July 14, 2018 2:43 PM
I agree on everything the blog has discussed above.
Reply to comment


Køb Herrreure og dameure on Sunday, July 15, 2018 11:24 PM
By for now Betty
Reply to comment


windows 8 recovery download on Wednesday, July 25, 2018 11:46 PM
MiniTool Solution Ltd. is a software development company based in Canada. As a dedicated software development company, MiniTool Solution Ltd. provides customers with complete business software solutions in the data recovery and partition management industry. Our affiliates and resellers all over the world are working hard together to deliver high quality software to satisfy our customers.
Reply to comment


Evan on Saturday, July 28, 2018 6:50 PM
We deserve to get the best treatment for ourselves and it we should always consider prioritizing it.Different time slots work according to the different business and their target audiences.linkI heard that, Cannabis and its components as a treatment for people with cancer -related symptoms caused by the disease itself or its treatment.Great content! It contains huge information about Supreme Court law.linkThank you for sharing this.This is one GREAT value-add! Evaluating your own environment program or security risks with an objective eye is difficult to achieve.link
Reply to comment


Click Here on Friday, August 03, 2018 3:08 AM
I must say you have done an excellent job with this. Also, the blog loads extremely quick for me on Chrome. Outstanding Blog!
Reply to comment

Add a Comment

Your Name:
Email Address: (Required)
Website:
Comment:
Make your text bigger, bold, italic and more with HTML tags. We'll show you how.
Post Comment