1995 F150 Lean Problem
#1
03-25-2012, 03:32 PM
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1995 F150 Lean Problem
I have a 95 5.0 F150 I bought recently. I've spent a lot more on this truck than I should have already...
It keeps showing a code 172 for Bank 1 being lean, I unplug the sensor and it's still lean. Unplugged the harness at the battery and still lean. The only thing I've found that is really weird is there is a pigtail for an IAT sensor. The IAT sensor was laying beside the intake next to an injector. There is no where for the IAT to go.
Other than that, the plugs are in good shape, the wires are in good shape, the cap and rotor are fine also. I get the 172 with an oxygen sensor, with no oxygen sensor plugged in and without the harness at all. I also have no temperature reading showing on the dash. I don't know if these are seperate issues are could be related some how due to a harness problem.
David
It keeps showing a code 172 for Bank 1 being lean, I unplug the sensor and it's still lean. Unplugged the harness at the battery and still lean. The only thing I've found that is really weird is there is a pigtail for an IAT sensor. The IAT sensor was laying beside the intake next to an injector. There is no where for the IAT to go.
Other than that, the plugs are in good shape, the wires are in good shape, the cap and rotor are fine also. I get the 172 with an oxygen sensor, with no oxygen sensor plugged in and without the harness at all. I also have no temperature reading showing on the dash. I don't know if these are seperate issues are could be related some how due to a harness problem.
David
#2
03-25-2012, 07:16 PM
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When you unplug the HEGO sensor, it generates no signal. The PCM reads this as very, very lean and goes into fault mode which is to richen the mixture to the max open loop setting and retard the timing. This costs you both performance and economy. I suspect that either the sensor or the wiring is faulty. First of all do a continuity check on the wirin harness to make certain it's OK. Then you need to get a hold of a service manual and read the test procedures for the HEGO sensor. Typically they crap out somewhere around 60-80K miles so you maay just need a new sensor but TEST YOUR OLD ONE FIRST.
The IAT sensor is almost as critical to function. It needs to be connected and reading the ait temperature in the intake. Did some fool put an aftermarket air intake on this truck and not bother to re-mount the sensor? You did not say whether your engine has the MAF control or the Speed/Density control. It makes a difference in where the sensor was supposed to be. With MAF it's in the airbox top; I'm not sure where it goes with S/D
The IAT sensor is almost as critical to function. It needs to be connected and reading the ait temperature in the intake. Did some fool put an aftermarket air intake on this truck and not bother to re-mount the sensor? You did not say whether your engine has the MAF control or the Speed/Density control. It makes a difference in where the sensor was supposed to be. With MAF it's in the airbox top; I'm not sure where it goes with S/D
#3
03-25-2012, 08:05 PM
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It's speed density. To my understanding the IAT should be right behind the distributor. It has a very short pigtail so I'm not sure. I've repaired the harness but didn't know that instead of showing open it showed lean. I guess I could ohm out the main engine harness.
On a side note, my 94 with MAF doesn't have a pigtail for the IAT in that location where this one does.
On a side note, my 94 with MAF doesn't have a pigtail for the IAT in that location where this one does.
#4
03-25-2012, 08:28 PM
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Well, after finally finding a picture of the IAT location it's pretty obvious I have a MAF lower instead of the Speed Density one that has the IAT behind the distributor. I just found a lower with the rails, injectors, etc for 85 shipped on ebay though so 
I was questioning the injectors leaking down anyway so it will hopefully work out.
Now I just have to chase the threads for the oxygen sensor and replace it. Was pretty obvious it was in bad shape.
I was questioning the injectors leaking down anyway so it will hopefully work out.Now I just have to chase the threads for the oxygen sensor and replace it. Was pretty obvious it was in bad shape.