98 4X4 5.4L Idle rough P0171 Code
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98 4X4 5.4L Idle rough P0171 Code
1998 F-150 4X4 5.4L
Started idleing rough (periodically) and OBD II code P0171 (System too Lean (Bank 1) ) sometimes appears. Runs great at drive RPM. Only idles rough. Any ideas?
Thanks
..Mitch
Started idleing rough (periodically) and OBD II code P0171 (System too Lean (Bank 1) ) sometimes appears. Runs great at drive RPM. Only idles rough. Any ideas?
Thanks
..Mitch
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From: St Louis
It's a vacuum leak, not the MAF.
Uncommanded EGR flow due to an EGR valve not fully closing can also cause this symtom without throwing any EGR-related DTCs.
Steve
Uncommanded EGR flow due to an EGR valve not fully closing can also cause this symtom without throwing any EGR-related DTCs.
Steve
Last edited by projectSHO89; Oct 15, 2006 at 08:39 AM.
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Bad idle
Hey Meratzloff, I feel your pain. I have the same problem with my 99 5.4L f150. Been giving me fits for about a year. The big things are what have already been posted here. Check all the vaccum lines and rubber elbows for leaks/rot. I was told that O2 sensors do this often. Check the MAF, EGR, DPFE, but it will prob be due to O2 sensors. If you find the cause let me know. I am about to the point that I'm going to try changing the computer out. Good luck-Craig
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From: North Texas
Originally Posted by projectSHO89
It's a vacuum leak, not the MAF.
Uncommanded EGR flow due to an EGR valve not fully closing can also cause this symtom without throwing any EGR-related DTCs.
Steve
Uncommanded EGR flow due to an EGR valve not fully closing can also cause this symtom without throwing any EGR-related DTCs.
Steve
I actually agree with you. Just thought that doing the easiest, simplest fix first made sense. The MAF could easily throw this code. I guess it depends on what meratzloff meant by "idling rough". If it's idling like it has a vacuum leak, then it's pretty obvious.
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Sorry for the late reply folks. Finally got to work on it. Cleaned MAF per procedure and checked for any vacuum leaks. no luck. Intermittantly idles rough, then high, then normal, etc. Very annoying. Again, runs good at high RPM. Will try to check O2 because I think I know where that sensor is. Not getting any EGR related DTCs. Onlt lean bank 1 and 2 (P0171, 174). BTW. also replaced PCV valve. Only hose I cannot check for leaks very good is the hose that goes from the PCV valve to the back of the engine. Others look pristene. HELP!!??
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From: BC, Canada
The PCV hose is the most common one to leak.
Check the elbow in the hose where it attaches to the back of the manifold.
Check the elbow in the hose where it attaches to the back of the manifold.
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You might also try cleaning the egr passage. You will have to remove the throttle body and the egr valve. This is a common reason for rough idle.The carbon builds up bad in this area. I have a 99 f150 w/5.4 and this caused my problem. Although mine coded for it, they sometimes do not. This problem arises once you start building up some miles. Good Luck,
Allen
Allen
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It's fixed
Went ahead and took it to a reputable mechanic. It was the PCV hose (at the back) plus he cleaned the throttle motor (also at back of engine). Also went ahead and ran a can of engine cleaner (3M??).
Not too bad on cost ($200). Worth it. Running good now. Thanks to all who replied. This forum is great!
Not too bad on cost ($200). Worth it. Running good now. Thanks to all who replied. This forum is great!
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