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Hey guys got a question that I think I have the answer to but want to make sure. Truck is a '95 f250 4x4 5.8 e4od transmission. So yesterday after running the truck for about 10 min shut it off then went to start it 10 min. Later it idled about 200 rpm then 10 seconds later the idle goes up to about 1000 rpm and runs fine from there. Today leaving home depot it did it again idled about 200 rpm. I tried to give it gas but it just stayed but idled at 200 rpm for about 20 to 30 seconds then went up to 1000. I'm thinking iac valve cause I've had it before on a different vehicle 15 to 20 years ago. PLEASE let me know what you'll think. Any and all help greatly appreciated.
Ok so was able to pull codes but there hard to figure out. I got 2 x 159= 1 blink pause 5 blinks pause 9 blinks long pause. The other is hard I get a 1 blink pause 1 blink pause 2 blinks I've got that twice but the I get a 1 blink at the end. To shorten it 159 , 159, 112, 112, 1 what am I doing wrong?
Let me check those codes, I'll get back to you in some hours (I'm about to sleep, and the book is in the truck). Anyway, there is a lot you could do right now, take out and clean the IAC (there is a procedure, look for it), clean the throttle body, if the filters are old you could change the air and fuel filters.
I would pull the computer and open it up to check the caps for leaks first as this might be a bad 5 volt supply.
112 more than likely was from a cold engine.
Continuous Memory DTCs 112 indicate the sensor signal was less than the Self-Test minimum of 0.2 volts. The DTC was generated under normal driving conditions.
Possible causes:
-- Damaged IAT sensor.
-- Open circuit in harness.
-- Grounded circuit in harness.
-- Powertrain Control Module (PCM).
DTC 159 indicates the Mass Air Flow (MAF) sensor is out of Self-Test range and that the MAF signal was greater than 0.70 volt during Key On Engine Off (KOEO) Self-Test. Engine Running DTC 159 indicates the MAF signal was not between 0.20 and 1.50 volts during Key On Engine Running (KOER) Self-Test.
Possible causes:
-- MAF sensor partially connected.
-- Damaged MAF sensor.
-- Air leak before or after MAF sensor.
-- Damaged Idle Air Control (IAC) solenoid.
-- Damaged Powertrain Control Module (PCM).
Thank's guy's for replays. Looks like I have some work to do. I report back what I find.. Subford, do you think I should check the pcm caps first or test the maf and iac first? I'll also clean the maf sensor. Again thanks you'lls help is appreciated.
Wow, haven't seen a Ford PCM that used aluminum can capacitors.
The pictures were clean, but also, both caps look like they have a brown discoloration at the base of the board.
I can't magnify the pics further but you may want to double check those.
And yes, I agree with the corrosion part. Use some MAF or Electronic cleaner and a Q-tip and remove as much as that as possible. Do the same with the male part of the harness plug to.
The 1st and second picture of the same capacitor shows a likely problem.
The 2 traces are brown from perhaps excessive voltage or heat. Is there any liquid residue around the base of either cap? If there is ANY, that cap(s) are dead. Being a solid can capacitor, they won't show obvious signs as their lower counterparts of bulging or leaking. I would question that capacitor in the 1st picture.
You can't Ohm out those capacitors. They are rated in Microfarads. You would need a capacitance meter or a way of checking their capacitance.
But with the age of them, it's only a matter of time when they fail, not if.
Hopefully others will chime in for help.
I'm unsure of the resilience of solid can capacitors.
My only concern is the capacitor with the adjacent traces being dark brown from either over voltage or heat.
