1991 F-150 thanks for you're help , the air flow sensor appears to be of a diaphragm type and the coil with it when pressed in on , the pin end , it didn't change the electrical resistance at all

Hi Chris.

p0304 = Number 4 Cylinder Misfire Detected

Faulty spark plug 4
Clogged or faulty fuel injector 4
Faulty ignition coil 4
Fuel injector 4 harness is open or shorted
Fuel injector 4 circuit poor electrical connection
Ignition coil 4 harness is open or shorted
Ignition coil 4 circuit poor electrical connection
Insufficient cylinder 4 compression
Incorrect fuel pressure
Intake air leak

The P0304 code means that the cylinder 4 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 4.


p0102 = Mass or Volume Air Flow Circuit Low Input

Faulty mass air flow sensor
Intake air leaks
Dirty mass air flow sensor
Dirty mass air filter
Mass air flow sensor harness is open or shorted
Mass air flow sensor circuit poor electrical connection

Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow sensor cleaner.
Reset code and drive vehicle.
If the code comes back, it may be necessary to replaced the mass air flow sensor.


p0154 = O2 Sensor Circuit No Activity Detected Sensor 1 Bank 2

Faulty Front Heated Oxygen Sensor Bank 2
Front Heated Oxygen Sensor Bank 2 harness is open or shorted
Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

Replacing the Front Heated Oxygen Sensor Bank 2 usually takes care of the problem.


p0113 = Intake Air Temperature Sensor Circuit High

Faulty Intake Air Temperature (IAT) sensor
Dirty air filter
Intake Air Temperature (IAT) sensor harness is open or shorted
Intake Air Temperature (IAT) sensor circuit poor electrical connection

The Intake Air Temperature (IAT) sensor is built into mass air flow sensor or in some vehicles mounted to the air filter duct housing. The sensor detects intake air temperature and transmits a signal to the Engine Control Module (ECM).The temperature sensing unit uses a thermistor which is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in response to the temperature rise. The Intake Air Temperature signal is used as an input for various systems in the vehicle.



Hope this helps
FYT

http://www.autocodes.com/make/nissan

-Not always the plugs and the coil case this. This can be cause by bad injector. Dirty mass air flow sensor.
-First Clean mass air flow sensor. If it's still do the same thing
then check the resistance of every injector. If it's not within its specification then replace it.

Good Luck

Mai

Make sure the air cleaner is clean.
you can spray clean the mass air flow sensor which is in the air supply tube after the air cleaner.
my guess is the throttle position sensor is not working correctly, it can be checked with an ohm meter. it is located where the gas throttle connects to the engine, and regulates the gas flow it speed up the engine. sometimes when not working correctly, you will also smell gas. Resistance between two of the pins will change as the center is rotated. pins are small and hard to get clips on, so I use small pieces of stranded copper wire with 1" insulation with most of the strands removed, leaving several sticking out a bit and bent so they won't push into the insulation when the almost hollow insulation is pushed onto the pin. leave some wire sticking out the end so you can alligator clip test leads to it. If in a hard to reach place, take it off of the engine and test.

try changing sensors, air flow sensor,coil pack sensor,or even the coil pack could be a possible solution.when was the last serviced,,

INTAKE AIR SENSOR,,OR COILS,IF IT SHAKES WHEN YOU PRESS THE GAS AND SOUNDS LIKE THOU THOU THOUSHOELIKE COUGHFIN THATS THE COILS OR THE MASS AIR FLOW SENSOR

P0101 ISUZU - Mass Air Flow Circuit Performancehttp://engine-codes.com/p0101_isuzu.htmlForum CodePossible causes- Dirty mass air flow sensor
- Dirty mass air filter
- Mass air flow sensor harness is open or shorted
- Mass air flow sensor electrical circuit poor connection
- Intake air leaks
- Faulty mass air flow sensor
Tech notes Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow sensor cleaner. Reset code and drive vehicle. If the code comes back, it may be necessary to replaced the mass air flow sensor

Hi Iler, have you replaced the air cleaner element and the fuel filter? Take it for a scan and that will pin point the problem. It would seem to me there's a problem with the air flow sensor. Regards Johngee10

Rather than take a stab in the dark replacing items - get the codes scanned and this should show what area the fault lies in. Normally if there is a fault with the MAF (mass air flow meter) it would normally show as a check engine light (MIL) - is this warning on? So many things can affect these engines from O2 sensors, coil misfires, bad cable connections etc etc. - so best move get the car scanned. Hope this helps (and saves money) good luck.

I have a 2002 Lesabre that had the same type symptoms. It ended up being the ignition control module. It cost around $150. It sits under the coils on my car. Had a somewhat large plug going into it. Not too difficult to replace.

Hope that helps.

No, no need to replace everything. There is a sensor, Mass air flow, located in one of the metal tube sections of your intake manifold. The qires will give it away. Pick up some CRC electrical spray cleaner and wash that sensor as good as you can without brushing, rubbib=nf r otherwise touching Do not use compressed air, it will dry quickly on its own. Seeif this saves you a few bucks. Your air cleaner/filter needs to be kept clean and leak free. The MAF controls your fuel and will shut down the engine if it doesn't sense the intake air. If you doubt your coils, watch under the hood after dark. If you see a light show, Replace whatever is letting the spar escape. and it wouldn't hurt to have the plugs gapped at specs. Good Luck, Ned-