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Discussion Starter #1
This is what one of the error codes read when I had it scanned, along with random cylinder misfire and misfires detected on cylinders 1 through 6. It's only missing when it's at idle but I guess it's the fuel trim malfunction causing it. Anyone know what could be the problem causing this code?
 

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BradleyD said:
This is what one of the error codes read when I had it scanned, along with random cylinder misfire and misfires detected on cylinders 1 through 6. It's only missing when it's at idle but I guess it's the fuel trim malfunction causing it. Anyone know what could be the problem causing this code?
what is the exact code that is being set. Do you have just a fuel trim code or do you also have misfire codes. p0300 is a random/multiple misfire code and can be caused by bad spark plugs or wires as well as many other things. Fuel trim codes can be set for multiple reasons as well. If you post the code numbers you I might be able to help a little more.
 

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Do you have any mods? Are you supercharged? We need more info. on your truck.

Robert
 

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Take a look at the MAF sensor. The P0170 makes me suspect it is clogged or burned out completely. The misfires on all 6 cylinders likely a result of the ECU trimming back fuel because it does not see enough air flow across the hot wire. The K&N makes me think so even more. Did you recently re-oil it?
 

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Discussion Starter #8
I haven't recently reoiled because I replaced it with the stock paper filter a couple of weeks ago. How can I go about checking the MAF sensor to make sure it's reading properly?
 

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I'd give it visual inspection before you try giving it a functional chec. See if the little elements of the sensor hanging down into the intake are dirty. I wouldn't drive around much either with the misfires occuring. You can F your truck up bad if you do.
 

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lots of people have had problems with the k&n filter and maf contamination. The air filter is close to the maf and you can get some of the oil sucked off the filter and coat the sensor and throw it off. This may cause a lean misfire. do a visual check like akshunj was saying you can also take some electrical contact cleaner and spray the wire element of the maf and clean it then reinstall it and see if the misfires quit. just make sure you clean it with a non-residue cleaner like electrical contact cleaner or it can leave stuff behind that will throw the sensor readings off. I have also seen some el cheapo paper filters shed some of the paper fibers and have the maf contaminated with the fibers.
 

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Discussion Starter #11
One more question about this before I take it to a shop. Hooked the truck up to a friend's scan tool and the MAF sensor seems to be reading the correct amount of air flow (according to the Haynes manual) with the correct intake air temp, but could an O2 sensor cause this. Correct me if I'm wrong, but the Haynes manual says the sensor should fluctuate between 0.1 to 0.9 volts when it reaches operating temp, but the voltage readings I got drops below 0.1 volts and has a few readings of 0 volts. Could this be a sign of a bad O2 sensor causing this problem?
 

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I'd have to say no. If your friend's scanner can read the MAF sensor and IAT sensor have him look at the lont term fuel trims. I would imagine they are all negative values. Did you ever look at the MAF sensor? Was it clean?

If the O2 sensor was bad, the ECU would not go into closed loop operation after a cold start which would trip the P0125 code.
 

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Discussion Starter #13
Yes, the long term fuel trim was about -7%. I looked at the MAF sensor and couldn't see anything on it, cleaned it anyways with no change.
 
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