Hi guys! My mechanic and I are baffled by a P0141 and P0142 code problem on my 2004 Expedition 5.4l. The message says that there is a lean mixture problem. Recently, I had a full service done to the engine, injector cleaning, tune up, oil change, etc. After that, the engine's idle was very smooth, but once I got up to about 70 mph, the service engine light came on, and then it had a very rough idle. I took it to a mechanic and he said that a spark plug cap was loose and he fixed it, and then it was fine again, until I got to that speed on the highway. The rough idle is back and, if I start it with the A/C on, it will make a slight sound. I moved to another city, so another mechanic scanned it and he got those codes back. He checked for loose valves or vacuum leaks, but couldn't find anything. He has mentioned to me that I have normal spark plugs and that he recommends at least platinum spark plugs, but he sees no reason for them to fire up that problem code. Could this cause the problem? Every time he scans and resets, the service engine light goes away, but I hit the highway and speed and it turns back on. Even with the service engine light off (it's off right now, which is what really baffles the mechanic), the car feels rough, and I feel that it's giving me less mpg's. I am thinking of replacing the spark plugs anyway, but I wonder if this would really solve my problem. I haven't replaced the sensor yet. Any help would be greatly appreciated, thanks in advance!
Help with P0141 and P0142 codes on a 2004 Expedition
- Thread starter xavimung
- Start date
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Lane24
technical advisor
Try cleaning your MAF ... look through this link... pretty much anything and everything about rough idles in here.. http://www.expeditionforum.com/showthread.php?t=4926
Lane24
technical advisor
That one looks like it was posted in June. Before the 2 sites merged, so alot of the more experienced members had all vacated to the new site. We're all back now so ask away !!!!!
We try not to ignore anybody... sometimes if a question isn't answered right away, you can give it a bump and it will show up at the top again..
Explor2Exped
Full Access Members
I HATE THOSE EFFIN CODES!!!!!!
I've done everything possible to slash out those codes & I keep getting the running lean one.
My solution was easy (not a healthy one) All I did was reset the expy. No more CEL still running lean I know... but no CEL hah... I'm getting 14mpg so I'm alright with that fuel mixture.
I've done everything possible to slash out those codes & I keep getting the running lean one.
My solution was easy (not a healthy one) All I did was reset the expy. No more CEL still running lean I know... but no CEL hah... I'm getting 14mpg so I'm alright with that fuel mixture.
dougmcp
Full Access Members
If the codes you are getting are the P0141 and P0142, it's likely the rear O2 sensors and not a lean mixture at all. The fix is either change the O2 sensors or install O2 extenders on the rear sensors.
Lane24
technical advisor
I know of a lot of people who have replaced those sensors, and still get the code.
Explor2Exped
Full Access Members
I checked all of the O2 sensors & they all look pretty brand new. No rust, corrosion or anything...
dougmcp
Full Access Members
Like all electronic devices, O2 sensors can look brand new and still be defective.
Your O2 sensors do 2 things, the front ones set the fuel mixture/ratio and the rear ones check for cat operation.
People who chip their vehicles for more performance/power install O2 extenders on the front O2 sensors which supplies more fuel and results in more power.
Rear O2 sensor extensions are installed to get rid of the pesky P0141 and P0142 CELs by reducing the temperature reading of the sensor.
Your O2 sensors do 2 things, the front ones set the fuel mixture/ratio and the rear ones check for cat operation.
People who chip their vehicles for more performance/power install O2 extenders on the front O2 sensors which supplies more fuel and results in more power.
Rear O2 sensor extensions are installed to get rid of the pesky P0141 and P0142 CELs by reducing the temperature reading of the sensor.
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