engine running rough. don't know whats wrong
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From: oceanside ca
engine running rough. don't know whats wrong
i have a 99 f-150 4x4 with a 5.4 engine. the engine is running realy rough. i wasn't sure but i thought it might be a fuel problem so i changed out the the fuel filter, that didn't help. so i then changed out the spark plugs and still nothing. i hooked up a scanner and it came back with the code P0171 system too lean (bank 1). i think that is the O2 sennsor before the CAT but i don't know how to tell witch one(driverside or passenger side). i think the O2 sennsor send a reading to the computer and then the computer adjusts the fuel accordingly. if the O2 sennsors bad i think if could mess up the way the engine is running due to to much or to little fuel. in this case i think im getting to little. this is just a guess i realy not to sure but thank you for your help.
Laughing Gas
Joined: Aug 2004
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From: Portsmouth, VA
Yup, you probably are in need of a new Oxygen Sensor. Lean means that the system is not getting enough fuel into the mixture. How many miles do you have on your truck? I've heard, do not know how true it is, but they need replaced around 90,000 miles?
- Chris
- Chris
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Joined: Sep 2006
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Check your vacuum lines b4 you go and pay and deal with 02 sensors! They can be expensive! If your on a budget that can't afford to play around in the cold, But if you do ultimately find you need new 02 sensors heres an ebay site I think you'll find are amazingly cheap! They might get you threw inspection, maintain your gas millage, make the code go away, how they perform, and how long they will last, I don't know? But the price is well "you make the call, check it out but check for vac leaks first. Good Luck http://stores.ebay.com/GLOBAL-AUTOMOTIVE
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Here is a more direct link there are Bosch, ya goota look around. There cops are like WoW cheap http://cgi.ebay.com/ebaymotors/NEW-B...mZ160024027277
Hotshot
Joined: Jan 2004
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From: St Louis
O2 sensors seldom, if ever cause "lean" codes (P0171 & P0174).
These codes are almost always due to a leak that causes the sensor reading to skew. They do NOT mean the engine is running lean. They mean the computer has maxed fuel enrichment (rich) but the o2 sensor is still reporting the exhaust as lean. Any additional air in the system, either in the intake past the MAF sensor or in the exhaust prior to the upstream O2 sensor, will cause the reading to show lean.
Steve
These codes are almost always due to a leak that causes the sensor reading to skew. They do NOT mean the engine is running lean. They mean the computer has maxed fuel enrichment (rich) but the o2 sensor is still reporting the exhaust as lean. Any additional air in the system, either in the intake past the MAF sensor or in the exhaust prior to the upstream O2 sensor, will cause the reading to show lean.
Steve
Last edited by projectSHO89; Dec 4, 2006 at 06:51 AM.
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From: oceanside ca
fixed it
i scanned the truck again and got a "system too lean (bank 1) and (bank 2)"
i google that and a site came up that told me that the MAF sensor was probibly dirty. they say that you can't clean them but the site also told me how to clean it. all you have to do is go to the local Radio Shack and get a can of spray tuner cleaner, #64-4315 spray it on and let dry make sure that you don't get to close cause it will break the wire in side.
i google that and a site came up that told me that the MAF sensor was probibly dirty. they say that you can't clean them but the site also told me how to clean it. all you have to do is go to the local Radio Shack and get a can of spray tuner cleaner, #64-4315 spray it on and let dry make sure that you don't get to close cause it will break the wire in side.
4wd Low
Joined: Jun 2006
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I had similar symptoms with my 1999 F-150 with the 5.4L. It turned out the EGR valve was sticking and we thought just cleaning it up would probably fix it. 4 days of troubleshooting later, we wound up replacing the sensor and control valve that tell the EGR valve what to do. When it malfunctions, it allows air to flow into the system and "lean out" the mixture. Basically, a big vacuum laek that will come and go. Ford has re-designed the replacements and they don't look much like the old components. That probably says something about the reliabilty of the older design. Really hard to complain though, this failure occurred at 128,000 miles! Ford part numbers for the new components are F77Z-9J460-AB for the sensor, and F63Z-9J459-AA for the control valve. It is possible that one of these components that we removed is still good, but after a lot of screwing around, we just replaced them both. This was a time consuming diagnosis as we thought it was for sure a cracked coil or dirty injector. The EGR valve would set a code, but we thought it was just "sticking".
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