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Mass air flow sensor and more


jandm9002

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Here is my trouble. I have a 1994 B4000 4X4. On the way home the truck died. It idles but when you give it gas the revs drop off.It was diagnosed as a bad mass air flow sensor.I purchased a brand new mass air flow sensor and installed that, testing the wiring at the connection as well. Ground, power, and power from the computer . All check out. The new mass air flow sensor does nothing that the old one did. Exactly the same situation. It idles roughly and revs drop off as you give it gas. If you disconnect the mass air flow sensor the truck runs fine, idles properly and runs well. Is there some sort of reset with the computer to "introduce " the new mass air flow sensor? No other work has been done on the truck recently, no manifold work or anything like that. The truck runs fine without the mass air flow on but I would like it to run properly with it connected as it should. Any solutions from anyone who has had the same experience or hints and ideas are appreciated.
 


RonD

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Welcome to TRS :)

How/who diagnosed it as bad MAF sensor?

To reset computer unhook battery for 5 min, or unhook one cable on the battery and touch it to the other battery cable, that drains capacitors in computer instantly, then hook battery back up.

You can easily get trouble codes from 1994 Ranger/B-series by using the CEL(check engine light) and counting the flashes

Video of that here: https://www.youtube.com/watch?v=X07hu0kAuzE

You need a short jumper wire, and that's it :)
Very very good thing to know how to do, for 1994 and older vehicles, knowledge is POWER


It could be the Computer itself is the problem, which is why you should do the above test and read the code.
24 years old can mean the capacitors inside the computer have failed and leaked
You can remove the top of computer and have a look inside.
Should look like this: http://www.auto-diagnostics.info/ford_eec_iv

The 3 Blue capacitors are what failed and leaked, they can be replaced for a few dollars
 
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rangerenthiusiast

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Fuel pump? Or clogged fuel filter? Bad vacuum leak?

Seems like almost every mechanic out there wants to jump right to the MAF right away. I had a guy “diagnose" my 2000 Jetta as having a bad MAF when it was only 5 years old. There was nothing wrong with it. Probably a big mark up on the part and easy to change out.

Hope you find the issue soon.
 
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jandm9002

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Thanks for the input there. I am going to look into the bad computer situation. I have had the battery disconnected for weeks at a time so it would have easily reset at that point. The Youtube video is exactly the same as under the hood of my truck. I presently have the mass air flow sensor disconnected, I imagine that should be reconnected in order to run the codes?Will it show a code for a bad computer?
 
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RonD

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MAF sensor can be left unplugged

You will just get a code that it is not working, if you have driven it without MAF connected

Codes mean computer is working, you can "talk" to it, or rather it can "talk" to you by outputting codes.
If the computer gives you, no codes or "oddball" codes, or multiple codes for "working" systems then computer is the problem.

There is no "computer test" for vehicle computers, code 111-System checks OK is about the only one there is


1994 will use 3-digit codes, list is here: http://therangerstation.com/tech_library/3digitcodes.shtml

Trick with ALL OBD codes, OBD1 or OBD2, is to also look at codes computer did NOT use.
Computer will have a few codes each for O2 sensor, MAF sensor, Temp sensor, or ect....
The ones it didn't chose can tell you what the problem isn't :)
 

jandm9002

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Thanks for the education, greatly appreciated. I will get around to looking into his in the next few weeks. If I get this solved I will post the results hopefully to help out anyone else who runs into this.
 

jandm9002

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Solved the Mass Air Flow problem. I got a refurbished computer from ebay and swapped it out which has solved the problem.
If a person was looking to replace a computer on their vehicle I would recommend Pro-Rebuild on ebay. They are located in Maryland. I am on the west coast of Canada and they shipped quickly and included a prepaid FedEx label for return shipping of my old computer for a core charge. Very satisfied with them, well worth looking into.
Replacing the computer wasn't too much trouble. Absolutely not necessary to remove the inner wheel arch cover at all. I removed the cruise control diaphragm from the drivers side of the inner fender. Then pull off the plastic housing over the wires going into the computer. There are 4 plastic clips that need to be pried up holding it on. Then unbolt the computer wiring and push it aside. There are two nuts holding the computer in place. Top one is easy to get to. On the bottom one I used a long series 1/4" drive 11mm socket. The over all length of the socket by itself is 2". Any longer and it probably wouldn't work, slightly shorter it would be easier but this worked for me without too much fuss. Place the socket on the nut then after the socket is on the nut then engage your 1/4" socket drive. Lots of small ratchets until the nut comes loose then you can spin it off with your fingers. The computer then pulls out of the firewall. Probably about 30 minutes to remove it including help from a 13 year old and figuring out which sockets to use. Thanks for the input everyone.
 

RonD

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Good work :icon_thumby:

Thanks for the update and FIX
 

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