Check Engine Light/Running Lean
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Check Engine Light/Running Lean
My check engine light keeps coming on about every 6 months (assuming I reset it) and reports that I am running lean. Has anyone else had this problem, and if so, how did you go about fixing it? Do I need an oxygen sensor replacement or something else?
Edit: I should also mention that it idles pretty rough on a cold start.
Edit: I should also mention that it idles pretty rough on a cold start.
Last edited by ethangar; Feb 21, 2004 at 09:51 PM.
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I have a 97 XLT 4.0 SOHC V6 and the engine light was on/off intermittently. It ran rough all the time but worse when cold. The codes indicated O2 sensor slow to respond. I replaced the (3) O2 sensors but it still ran rough. I checked the plugs for crud and found one with a cracked tip. Seems that when the O2 sensors fail you run rich or lean. I was running lean and early detonation can cause a plug tip to crack.
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My 2001 sport trac did the very same thing V6 SOHC, and after looking everything over I found that my pvc valve was not working right, replaced it and everything has been fine ever since.
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Cargo Master
Joined: Oct 2003
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From: Jefferson, Iowa
Take a vaume test, that would let you know. Also that could be causing low MPG if you have that, because a vacume leak wouldthrow the MAP sensor off.
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From: North Texas
Originally Posted by ethangar
My check engine light keeps coming on about every 6 months (assuming I reset it) and reports that I am running lean. Has anyone else had this problem, and if so, how did you go about fixing it? Do I need an oxygen sensor replacement or something else?
Edit: I should also mention that it idles pretty rough on a cold start.
Edit: I should also mention that it idles pretty rough on a cold start.
Just went through exactly the same symptoms with my wife's '01 Sport:
runs rough on (very) cold mornings, stumbles, sets lean codes for both cyl. banks, spark-knocked under light load. But got great gas mileage!
Replaced spark plugs (one had a cracked insulator tower) and wires at 76K miles; had no effect on symptoms.
Replaced fuel filter after treating ear for gasoline intrusion, bandaging cut on forehead...
Still no improvement.
Picking up truck this PM from trusted local mechanic who is replacing gasket under (plastic!) intake manifold; he told me he find leakers "all the time" on 4.0L SOHC engines with the plastic manifolds.
Now looking for an aluminum manifold from a pre-'01 SOHC engine.
Sounds like another one of Ford's "better ideas" in action...
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engine running lean
I just had the problem come up again and this time it was the line running from the pvc valve that runs around the back of the engine and then up to the front and then enters into engine just after the throttle body.
the leak was at the point where the plastic line from the pvc valve and the rubber line from the intake mate up, I had to buy the whole assembly from ford ( they do not sell just the rubber piece that was cracked ) and the problem went away.
the leak was at the point where the plastic line from the pvc valve and the rubber line from the intake mate up, I had to buy the whole assembly from ford ( they do not sell just the rubber piece that was cracked ) and the problem went away.
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From: North Texas
Originally Posted by Bud ward
I just had the problem come up again and this time it was the line running from the pvc valve that runs around the back of the engine and then up to the front and then enters into engine just after the throttle body.
the leak was at the point where the plastic line from the pvc valve and the rubber line from the intake mate up, I had to buy the whole assembly from ford ( they do not sell just the rubber piece that was cracked ) and the problem went away.
the leak was at the point where the plastic line from the pvc valve and the rubber line from the intake mate up, I had to buy the whole assembly from ford ( they do not sell just the rubber piece that was cracked ) and the problem went away.
Thanks; I neglected to mention I replaced that leaky part also!
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I have over 100,000 miles on my 2001 ST and other than the two leaks in the pvc system I have had no other problem with it.
It has started to ping a little whenever I accelerate though, it has the original plugs and wires and I am going to get them changed this week.
It has started to ping a little whenever I accelerate though, it has the original plugs and wires and I am going to get them changed this week.