Running Lean, whats the problem?
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Junior User
Joined: May 2004
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Running Lean, whats the problem?
My 2000 lightning started running bad, well first the service engine light came on, then I noticed some pinging under load, then some erratic idle and missing.
I had the codes checked, it's running lean on both banks, the troubleshooting says Oxygen Sensor, MAF, but I have headers with 2 oxygen sensors, so the chances of Both being bad is long, so I'm thinking MAF??????
This truck has MANY upgrades, will , if you think I'm right about MAF, a stock MAF be ok, or is there aftermarket for upgraded motors?
Also, I have to say, I noticed a small exaust leak on one header due to missing bolt- could this have an effect on Oxygen sensor malfunction? Although then thats on one side, why would the ECU say lean on both banks??
I had the codes checked, it's running lean on both banks, the troubleshooting says Oxygen Sensor, MAF, but I have headers with 2 oxygen sensors, so the chances of Both being bad is long, so I'm thinking MAF??????
This truck has MANY upgrades, will , if you think I'm right about MAF, a stock MAF be ok, or is there aftermarket for upgraded motors?
Also, I have to say, I noticed a small exaust leak on one header due to missing bolt- could this have an effect on Oxygen sensor malfunction? Although then thats on one side, why would the ECU say lean on both banks??
Mountain Pass
Joined: Feb 2004
Posts: 119
Likes: 5
Do you run a K&N air fiter? If so the MAF sensor may have oil on it which causes it
read wrong,or it may just be dirty from normal everyday use.I reccomend removing
the MAF and cleaning it with non-clorinated brake cleaner.This works the best for me.
Don't use carb or injector cleaner because they may leave behind a film. I am a auto
tech and have done this many time. I even do it as regular maint during a tune up
on all vehicles. If cleaning the sensor does not work, you may have to replace it.
Chances are both O2 sensors are not bad. Are there any other codes stored?
If not,check your fuel pressure should be around 40psi. It is possible the fuel filter
is clogged,or the pump is getting weak,but the MAF is the most common cause for
this symptom.
read wrong,or it may just be dirty from normal everyday use.I reccomend removing
the MAF and cleaning it with non-clorinated brake cleaner.This works the best for me.
Don't use carb or injector cleaner because they may leave behind a film. I am a auto
tech and have done this many time. I even do it as regular maint during a tune up
on all vehicles. If cleaning the sensor does not work, you may have to replace it.
Chances are both O2 sensors are not bad. Are there any other codes stored?
If not,check your fuel pressure should be around 40psi. It is possible the fuel filter
is clogged,or the pump is getting weak,but the MAF is the most common cause for
this symptom.
Thread Starter
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Junior User
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excuse my ignorance with the new elec/mechanical----I looked at it, seemed clean, but then by your discription I'm asuming oil or the (film) that can throw it off is probably something hardly visiable?
Also, when I took off the filter, there is engine oil all in the intake tube, is it coming from the pcv valve tube, or the straight through tube to the other valve cover? I can't really say cause the supercharger has been sucking it up all over the place, but I assume it's from the straight through tube, the one that enters the intake tube right after the MAF sensor housing??
Is this tube necessary?? I mean it enters between the MAF and the throttle body, so I don't think it would effect computer function? The bottom of the filter was caked with oil and dirt, so it's been coming in for some time. It's a K&N element.
also, is the stock MAF ok for a much upgraded engine, or is there an aftermarket version with better performance?
Also, when I took off the filter, there is engine oil all in the intake tube, is it coming from the pcv valve tube, or the straight through tube to the other valve cover? I can't really say cause the supercharger has been sucking it up all over the place, but I assume it's from the straight through tube, the one that enters the intake tube right after the MAF sensor housing??
Is this tube necessary?? I mean it enters between the MAF and the throttle body, so I don't think it would effect computer function? The bottom of the filter was caked with oil and dirt, so it's been coming in for some time. It's a K&N element.
also, is the stock MAF ok for a much upgraded engine, or is there an aftermarket version with better performance?
Senior User
Joined: Sep 2004
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From: New Joisey
I had codes of "lean bank" and "Low EGR Flow", but otherwise the truck ran ok. Check here http://www.f150online.com/forums/showthread.php?s=&threadid=122110&highlight=vacuum It turned out to be the EGR vacuum line was melted to the EGR tube. I couldn't see it without looking for it.
Lemmie know if the link doesn't work.
Lemmie know if the link doesn't work.
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Junior User
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I checked it out, and that vacum line is fine, is there a way to check for vacum leaks besides tracing every line, like a vacum gauge that can test total vacum??
Also, is it ok to replace old (hard) vacum line with rubber line, it is real thick, but I wondr about the vacum (sucking) the rubber shut?
Also, is it ok to replace old (hard) vacum line with rubber line, it is real thick, but I wondr about the vacum (sucking) the rubber shut?
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Junior User
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Now that I think about it, another thing I notice is when the truck is warm, if I shut it off, then restart it within say 5 mins, it starts rough sometimes now, like it's flooded, I would say choke if this was 10 years ago. Just an added symptom I notice, thanks to everyone who take the time to help!!
Senior User
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From: New Joisey
You can unplug the factory boost gauge from under the dash, right around where your knees are (there is a tee), and plug a vacuum gauge in it's place. I think you should be getting around 20 at idle.
Have you checked the spark plugs? Are all of the electrodes in tact and/or are they fouled with fuel?. You could possibly have a bad coil pack. One way to test that is while the truck is running rough, start unplugging them one at a time. If there is not change in how the truck is running when one is unplugged, it could be that coil pack that is bad.
Have you checked the spark plugs? Are all of the electrodes in tact and/or are they fouled with fuel?. You could possibly have a bad coil pack. One way to test that is while the truck is running rough, start unplugging them one at a time. If there is not change in how the truck is running when one is unplugged, it could be that coil pack that is bad.
Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
Since you have lean codes on both banks it is probably caused by unmetered air entering behind the MAF. It isn't uncommon for the PCV tubes to pop out of the intake bellows and cause the codes. It could also be caused by a vacuum leak. If you want to save yourself some headache, go to a shop and have them do a vacuum integrity test with a smoke machine. It will pinpoint the leak if there is one and should only cost about $40.
Senior User
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From: New Joisey
Yeah I guess a bad coil pack prolly wouldn't throw a lean code.
Another thing to check, and this also happened to me is the rubber intake boot. I had taken it off to clean the throttle body, and when I put it back on it folded underneath. It looked like and felt like it was connected, but when I took the boot back off I could see the fold, and a little slit in it. Also make sure the 3 vacuum lines underneath are plugged in.
Another thing to check, and this also happened to me is the rubber intake boot. I had taken it off to clean the throttle body, and when I put it back on it folded underneath. It looked like and felt like it was connected, but when I took the boot back off I could see the fold, and a little slit in it. Also make sure the 3 vacuum lines underneath are plugged in.
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well today I'm changing the pcv valve, cleaning the MAF, and I ordered a IAT sensor. I also had a bolt that was misssing from the header collector that was leaking at the donut a bit, and tightened up all other header bolts.
Funny thing, it's about 15 degrees cooler here today, and when I went to work this morning the truck was running great again, so I cleared the codes and the service engine light has stayed off. I thought about it and realized that it has been running bad on warm days, when outside temp is above 75 degrees, witch really sways me towards the IAT being bad, thinking it isn't working therefore reads cold, and hence when the air charge heats up on hot days, the air/fuel is not adjusted properly.
Funny thing, it's about 15 degrees cooler here today, and when I went to work this morning the truck was running great again, so I cleared the codes and the service engine light has stayed off. I thought about it and realized that it has been running bad on warm days, when outside temp is above 75 degrees, witch really sways me towards the IAT being bad, thinking it isn't working therefore reads cold, and hence when the air charge heats up on hot days, the air/fuel is not adjusted properly.
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OK, So I take off the 2nd valvecover breather line to the intake, the one thats straight through, I cap the intake, and ad a valvecover breather. I install a new PCV valve, clean up the MAF, and the IAT sensor. Well I give it a run, seems to be running better, oh and I tightned up the header bolts and the collector bolts, still didn't feel right. So I brought it home, took the MAF back off to see if there was a part number or something, and came up with an idea ( air enters the MAF body- 2" filter inlet in streams, so why not rotate the MAF to see if theres a SWEET-Flow spot)--and D@$, aftter 2 shots, or positions, she starts running like a bat out of @%#$!!!!! With codes cleared for 2 days now, no problems, oh I turned the IAT sensor also, to better match flow.
So, now, off to more power, see my next post, thanks!!
So, now, off to more power, see my next post, thanks!!