Hey guys, I have a 98 4.6 4x4. It had been sitting in the grage for about a month and I decided to fire her up and take her to work. Started up just fine and ran perfect. I went all day untill about 3pm. (250 miles, i filled up in the morning). Pulled in to post office and kiled it. Started it back up and it ran like crap. Shaking, no power, stumbling as it has to catch up with its self. Code p0113 and p0308. I am guessing the misfire code is coming from the other code/problem itself. Almost the same sexact thing happened to me a year ago and i replaced MAF and it was fine. I bough the cleaner and will try that. Any help appreciated . . . .

 

Had a similar thing happen. Ended up being a clogged injector.

 

A clogged injector can cause the mis on #8 but it's not going to cause the IAT high voltage code.. The IAT is built into the MAF. When you replaced it last time did you use Motorcraft? If not you should. Most likely it's the sensor but you should look at as much of the wiring going to the sensor as you can to make sure there's no short anywhere like corrosion in a connector or spot that's rubbed or pinched that could cause it.

 

I believe I did I will go check now. THe high circuit if I understand right is due to low temp. Im in indiana and it was 100 degrees that day...

 

The lower the temperature the higher the voltage, however the voltage is based off or referance voltage, 5 volts. The over voltage code will only come on when the sensor circuit sees over 5 volts, which is usually because of an internal short to battery voltage in the sensor.

 

So my next question is.... I have have a volatage meter.. what do I do? How can I test that and what voltage should I get?

 

I was kind of far off before, the code is triggered when the PCM sees over 4.6 volts on the IAT signal circuit. The IAT is a two wire sensor and if you're looking under the hood it's towards the firewall on the intake tube and left of the air box. With the key on unplug it and check the gray/red wire to make sure it's got 5 volts and not 12 and check that the gray wire has 0 volts and isn't shorted to power. The sensor has a thermistor that takes the 5 VREF volts from the gray/red and applies resistance based on temperature that lets the PCM know the air temp so if the gray wire is shorted to the gray/red it will show 5 volts, which is actually -46 degrees or something to the PCM which causes the code. As long as the gray/red has 5 volts and the gray has 0 you should be all set to replace the IAT.

Sorry about the confusion the sensors can be kind of complicated and changed some throught the years.

 

5.10 on grey and nothing on grey/red ( <-----is grey spelled with e or a? lol) So according to your last post you said that if I have these then I should be all set to replace the IAT? had to unplug it to test it. How did this test the actual sensor? I pulled the air filter and sadly it looks like it may be a little dirty. How can a filter get so dirty in such short time. Ill post up a pic. I do spend some time in the county going from job to job. We deal with a lot of farmer and grvel roads....

 

I took off the IAT sensor. Looking around online on how to test and this is what I found. I am not to familiar with thermistor and they way they work. I am told to set multimeter on 20K ohm setting. Touch black and red leads to sensor. Blow across sensor and it should change.

Results:

Set meter to 20 K OHM - default reading 1_._ _ _
touch red and black leads to eachother changes to 0.00 (complete circuit i assume

Touch to sensor and it shows as the leads are not touched 1_._ _ _

blow across it and nothing.

Is the above test true? and does my test mean its bad. Should it be a Normally Closed Circuit?

 

UPDATE:
Took the IAT sensor and hooked it up to the truck. Took Hair dryer also As I heat the sensor it drops voltage and when i switch it to cold air the voltage rises back up. Sensor is ok?????