I think it's the computer
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I think it's the computer
Ok, 93 f150 4.9 5speed. Truck all of a sudden started acting like it was running out of gas, pulled over and was idling very rough with a horrible exhaust stank-like truck is loading up:I think she's in full limp mode. Truck runs ok when on the throttle with a light load, but wants to die under heavier load. Tank is full-pulled codes and truck was bitching about EGR Position, MAP, TPS, and ECT all being out of range. Ohm/frequency meter on all sensors-acting normal. Here's the weird: I have no reference voltage on any of the aforementioned sensors(actually measured about .3V). Pulled the harness directly off the ECU and I've got zero resistance from there to each sensor. And-I have 5V on the MAP signal wire...WTF? Is there some goofy TSB problem I am unaware of, or is my paranoia of mis-diagnosis unfounded in anyones experience? Thanks for any help.
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vacuum leak? egr valve stuck? put vacuum on the egr valve and see what your evp sensor shows ohm wise. Thinking maybe you should check the fuel pressure.
may be totally undrelated. i once had an issue with the truck running horribly off idle first thing in the morning, spit sputter, fought me to get up to speed but once there, ran fine the rest of the day, turned out to be the distributor cap. you would think that was a fluke, but it happens every couple years.
may be totally undrelated. i once had an issue with the truck running horribly off idle first thing in the morning, spit sputter, fought me to get up to speed but once there, ran fine the rest of the day, turned out to be the distributor cap. you would think that was a fluke, but it happens every couple years.
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Yup-shows full voltage at the ecu and no resitance from fuse to relay, and relay to ecu. Same voltage/continuity checks on coil, ignition module, and dizzy. No resistance from ecu to ig. mod.-timing is super conservative. Full voltage/no resistance to the injectors and back to the ecu-injectors ohm ok. I'm convinced it's the computer shorted out inside, but I am too paranoid to just swap the ecu without some kind of consultation; they rarely go bad just by themselves too. Bout ready to rip harness apart and go Megasquirt II.
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Joined: Jan 2008
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From: Phenix city, al
Mine too, replaced just about every $20 part there is under the hood.
Did you ever pull a code in the mid 550's, like 555 556...?
Ambient Air?? My Air charge sensor, on the top side of the lower intake under injector 1...burnt like a old match stick...
=
had everyone telling me every possibility from coil, to fuel pump. Had the computer popping up EGR Position, MAP, TPS, and ECT all being out of range...
It's 16.99 at O'Reileys.... Unscrew, screw in, 2 wire connector...
Purrs... May not be your problem, but it beats buying an ECM and that not be the issue. ECM's just don't go out. You've got voltage to it, and all your other sensors are ohming out...
Don't know. I will tell you one thing. Everyone and I mean everyone told me that the Air Temp Sensor or Air Charge sensor, whatever they call it, wasn't causing my problems, "no way, Can't be that...BLAH BLAH BLAH.."
My 2 cents worth that cost me plenty of time, money and sweat sitting on the side of the interstate in rush hour in Atlanta...3 different times.
Did you ever pull a code in the mid 550's, like 555 556...?
Ambient Air?? My Air charge sensor, on the top side of the lower intake under injector 1...burnt like a old match stick...
=
had everyone telling me every possibility from coil, to fuel pump. Had the computer popping up EGR Position, MAP, TPS, and ECT all being out of range...
It's 16.99 at O'Reileys.... Unscrew, screw in, 2 wire connector...
Purrs... May not be your problem, but it beats buying an ECM and that not be the issue. ECM's just don't go out. You've got voltage to it, and all your other sensors are ohming out...
Don't know. I will tell you one thing. Everyone and I mean everyone told me that the Air Temp Sensor or Air Charge sensor, whatever they call it, wasn't causing my problems, "no way, Can't be that...BLAH BLAH BLAH.."
My 2 cents worth that cost me plenty of time, money and sweat sitting on the side of the interstate in rush hour in Atlanta...3 different times.
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Might help to make sure all your grounds are clean. IIRC there's one by the e-brake, left headlight area, by the battery and by the map sensor. There's also a relay for the computer. Recently I think I changed everthing listed in this thread and then some only to fix my problem by changing the fuel pump.
Do you still have two tanks?
Do you still have two tanks?
New User
Joined: Jun 2008
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Not that this helps but im having the same issuse but only when the truck is warm. (after 5 min of driving)
Idles rough and good luck trying to get up to speeds of 30+mph.
Started after i took my truck out wheelin (mudding) sence then sprayed the motor down 3 times.
88k orginal miles on my 88. sat for 10 years in a field.
I put 2k miles on it before this started.
Ive checked almost every sensor i can get my hands on and still no better.. cut off the cats and ran a cherry bomb now. Change both fuel pumps one in front tank and high pressure on the frame rail. Dont use the rear tank.
Idles rough and good luck trying to get up to speeds of 30+mph.
Started after i took my truck out wheelin (mudding) sence then sprayed the motor down 3 times.
88k orginal miles on my 88. sat for 10 years in a field.
I put 2k miles on it before this started.
Ive checked almost every sensor i can get my hands on and still no better.. cut off the cats and ran a cherry bomb now. Change both fuel pumps one in front tank and high pressure on the frame rail. Dont use the rear tank.
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Idling very rough with a horrible exhaust stank-like truck is loading up
Seems nobody else is picking up on this.
Does it smell kinda like rotten eggs or even burnt matches?
Dead and clogged cat will do that.
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Joined: Jun 2008
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i cut mine off and it didnt fix the problem.
New User
Joined: Jan 2008
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From: Phenix city, al
mine smells like I'm burning old gas, but not from the tail pipe. While it's running from up around the engine. Weird??
The other thing is while mine was not running right, (bad air charge sensor) it got 14 mpg highway, pulling 4000 lbs. Now it runs smoother, doesn't stall when hot, and only gets 11 MPG... stupid computer.
The other thing is while mine was not running right, (bad air charge sensor) it got 14 mpg highway, pulling 4000 lbs. Now it runs smoother, doesn't stall when hot, and only gets 11 MPG... stupid computer.
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Resolved.
Sorry to bump such an old thread but I did figure out the problem. I did not want to believe it was the computer, but it was. Here is a link to Megasquirt 2 install.
https://www.ford-trucks.com/forums/8...ll-w-pics.html
https://www.ford-trucks.com/forums/8...ll-w-pics.html