94 b4000 ground problem to maf

[lfsgood]

I brought it in and they said I have a ground problem to maf, cant afford hrs of them diggin around, Ive takin wire covers off about everywhere still dont see a bad wire? It didnt work to just add a wire and ground it to the engine, I believe its the power ground wire,, any help would be great ,, thanks

 

[Mirage]

It could just as easily be the power wire. But here's how to check... Grab your handy Haynes manual, and find the section on testing the MAF. It will show you the connector, and which wire is which. If I remember (but don't quote me on this) the left pin is the power the middle is the ground and the right is the signal to the ECM. With the ignition on but not running, check between the power and the ground. if you see voltage (check the bok to see exactly how much, but I think it's like 7 volts), if you don't see it take the ground lead to the block. If you still don't see voltage, you may have a problem on the power side. If you do see voltage, have a friend help by wiggling the harness and see if it mysteriously starts showing voltage. Slow and careful here as when you get voltage you have hound the break in the wire. Very often I find bad wires that are internally broken, but show no outward signs.

Hope this helps.

 

[lfsgood]

thanksn for the reply,,heres the newest,,for wires first red main power,10 volts then black,called power ground,, tan neg going to pcm and blue, signal. with it hookde up meter in signal ground off to chasis it goes haywire suppoes to be from .5 to 1.5 when you rev it up..when its acting up it will hit 12 volts. i ran new wire for tan and blue from clip to just before it goes into pcm,,i think something else is goin on .. so far i just have to disconnect maf ,not so great on the gas.thanks for any help

 

[Mirage]

Ok, you have a 4 wire MAF sensor. What you are concerned with is the Blue Signal wire and the Tan PCM ground. If you ground the Tan wire to chassis, you may cause a problem that doesn't actually exist. The MAF sensor takes 12V from the battery, and as in all 12V systems must ground somewhere, the chassis, eventually. Now the signal end of the sensor is the output from the sensor to the PCM. All the PCM cares about is seeing the proper voltage coming from the sensor, in a particular range. In your case .5 to 1.5V. The ground here is very imortant. It must be the same ground as the PCM. NOT THE CHASSIS! The two systems are separate, and crossing grounds can cause all sorts of wierd problems, including frying the PCM. So don't do that anymore. I could explain in detail why this is, but it doesn't solve your problem, so I'll save that for another discussion.

Anyway back to the problem at hand. So now you want to check out the the signal end of the sensor. First, make sure the connections to the PCM are tight. A loose connection could cause problems here. Once that is done, check out the MAF sensor connections. They should be clean, and make good contact. My wife hates it, but I use one of her nail files, or a small piece of emery cloth to clean the pins up. Just lightly sand them to remove any oxidation that may be present. Reconnect the MAF sensor and see if your problem goes away. (Be sure to clear any codes in the PCM, as it may use old data as a starting point, before it re-learns it's driving conditions. )

If the problem still exists, try wiggling the wiring harness, gentle and carefully, along the whole length of the harness all the way back to the PCM. We're again looking for a internal break in the wires. If there is no change, my first suspect is a bad MAF sensor, (they are a bit pricey, which is why I had you go through all these other steps first.) But I'm betting either a bad connection at the MAF, or the MAF itself.

Let me know what you find.

 

[lfsgood]

Ive checked my maf ,its good it runs fine for a bit then goes eratic.with the meter + in the the signal wire [ at maf] and - probe on ground the reading will jump at times to 12 volts, and like you said it should be 1.5.,I checked my cam shaft postion sensor and with key on Im only getting .35.. suppose to be 1.5.with that sensor unplugged cranking the truck Im not seeing anything with meter set on ac and in the 12 volt range. what is meter suppose to be set on? also when i back probe icm at wires 5,6 Im not getting anything, there is 12 volts on "8. Im gona go to auto store to see if the can check my icm, this is great fun. also my last ford Ill ever buy. thanks for your help

 

[shane96ranger]

also my last ford Ill ever buy

Because other brands make 17 year old trucks with no problems?

 

[Mirage]

Sorry you feel that way, I really am. I've had lemons before as well, but my Mazda, has been a dream. I've owned it for about 12 years now, and in that time only spent about $1000.00 in parts on it. (And that includes the right front fender, grill, and lights I had to replace after a cow walked out in front of me. Haha.)

But yes, it could be the ECM itself. They do go bad. But I'm pretty sure you can find one for under $200.00 if you look around. If the ECM proves to be the problem, let me know and I'll see what I can find for you locally. There is a shop near by in Stockton, Ca. that specializes in ECM's and they have real good prices, and I think an 18 month warrenty.

 

[lfsgood]

well , Id always been a chevy guy, but thats for a full sized truck. I went with the small one hoping ,and thinking maybe Id get 20 mpg. I could be getting 15 from a full sized truck. It does drive pretty well and I like the blue color,and pretty powerfull for a 6 cyl. Im sure ill be more happy once its running right again. It started off fine this am, when it started acting up I diconnected the red, main power and its like unplugging the whole thing( maf ) Im still trying to find out if and where I could get the Ignition control mod checked out, that throws out the signal to the crank sensor.. so many sensors. thanks again