Air Flow Sensor Problems
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Air Flow Sensor Problems
I have a 1990 Aerostar with the 4.0 and it started running rough just out of the blue, no warning. I looked for all the simple things first and just happen to unplug the air flow sensor while the engine was running and it smoothed right out. I took it to my local mechanic and showed him what happens when I plugged the A.F.S. back in and he told me that I needed to replace it.
I bought another one from Autozone (rebuilt) and I still have the same rough running motor until I unplug it. What do you think? Maybe I have a "new" bad one.
What is my next step?
1990 AWD 185,000 on second motor, third tranny.
I bought another one from Autozone (rebuilt) and I still have the same rough running motor until I unplug it. What do you think? Maybe I have a "new" bad one.
What is my next step?
1990 AWD 185,000 on second motor, third tranny.
Posting Guru
Joined: Nov 2003
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From: Homer, Alaska
Did you get a check engine light? Seems like if the maf was bad the computer would set the code. If the "new" sensor is doing the same thing as the old one, my guess is that's not the problem. mrshorty is right about checking the wiring. The Haynes manual shows how to check voltage to the maf sensor.
Post Fiend
Joined: Jan 2003
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From: Connecticut
Pull the code(s). It's doable without a scanner on your EEC-IV system: EEC-IV Code Retreival. Then address the codes. You can post them here for some more feedback...
Post Fiend
Joined: Jan 2003
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From: Connecticut
Ignore the initial "11" code.
It sounds like you are running lean if you got a "Key ON Engine Running" (KOER) code of 41. So you should look for reasons why your engine is getting too much air and/or too little fuel, such as vacuum hose/connection leaks, a failing fuel pump, clogged fuel filter or fuel injectors, PCV/Hose leaks, bad MAP sensor, etc.
As for your "Key ON Engine OFF" (KOEO) code of 96, that code is set when your PCM's fuel pump monitoring system didn't get the proper "All OK" signal from the fuel pump circuit. So you might want to look closely at the fuel pump.
For your reference, here is a good list of 2 digit codes:
http://www.dalidesign.com/hbook/2digit.html
It sounds like you are running lean if you got a "Key ON Engine Running" (KOER) code of 41. So you should look for reasons why your engine is getting too much air and/or too little fuel, such as vacuum hose/connection leaks, a failing fuel pump, clogged fuel filter or fuel injectors, PCV/Hose leaks, bad MAP sensor, etc.
As for your "Key ON Engine OFF" (KOEO) code of 96, that code is set when your PCM's fuel pump monitoring system didn't get the proper "All OK" signal from the fuel pump circuit. So you might want to look closely at the fuel pump.
For your reference, here is a good list of 2 digit codes:
http://www.dalidesign.com/hbook/2digit.html
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Rockledge,
Thanks for the information. I did notice when the KOEO test started my fuel pump made a gurgling noise. It kinda sounded like air bubbles being pumped into the feul tank.
75Ford250
Thanks for the information. I did notice when the KOEO test started my fuel pump made a gurgling noise. It kinda sounded like air bubbles being pumped into the feul tank.
75Ford250
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It sounds like you have a starting off point, anyway... 
Postmaster
Joined: Dec 2001
Posts: 3,742
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From: UT
One caution regarding the KOER 41. It's real easy to get that code if you didn't warm the O2 sensor up prior to the test. If you ran the KOER test on a cold or semi-cold engine, re-run the test and make sure the code stays there.
As for the 96, I've seen that one before if I try to start the engine after unplugging the inertia switch (like when you want to depressurize the fuel rail). If you don't see a fault in the fuel pump circuit, then clear that code (unplug jumper wire while codes are being output) and see if it comes back.
As for the 96, I've seen that one before if I try to start the engine after unplugging the inertia switch (like when you want to depressurize the fuel rail). If you don't see a fault in the fuel pump circuit, then clear that code (unplug jumper wire while codes are being output) and see if it comes back.
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I changed the fuel pump and I am sure glad I did it in the comfort of my garage instead of out on the road at a shop were I don't know anyones name. Unfortunatly for me that was not my problem. Not that the pump didn't need replaced, it did.
My problem is a vacuum leak in the brake power booster. It has an internal air leak. The Air flow sensor is fine but when I unplug it, that makes the van run better.
Thats for all the help with this. I have gain so much knowledge from this experiance and I love to know more about the amazing things about engines.
My problem is a vacuum leak in the brake power booster. It has an internal air leak. The Air flow sensor is fine but when I unplug it, that makes the van run better.
Thats for all the help with this. I have gain so much knowledge from this experiance and I love to know more about the amazing things about engines.
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