# ford exhaust manifold question



## davidluster (Sep 16, 2008)

2001 Ford F-150 5.4 V8 Triton


My CEL light came on about 6 months ago. codes were lean condition on bank 1 and 2. I cleaned the MAF sensor, cleaned K&N filter. Replaced PCV and hose, changed fuel filter (which was absolutely filthy, black gas) then ran three full tanks of premium gas with Lucas to clean injectors. CEL light has been reset several times and still comes back with same codes. I know that I have a leak in the exhaust manifold somewhere, hopefully just a needs a new gasket as the high pitched chirp/squeel is inconsistent and goes away when warm.

My question is this, if my leak is bad enough would that be enough to cause my lean condition?

Also anyone done this on similiar vehicle? I have heard on the 4.6 you have to raise the motor to remove the exhaust manifold but dont on the 5.4?


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## bwguardian (Aug 30, 2005)

The K&N filters are really good for diesels and not so good on gasoline engines...the oil messes with the sensors. I would try a paper filter element and clean the sensors again for the CEL...now the code may be the gasket.


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## PasadenaMan (Dec 5, 2007)

On another forum I am a member of, many peopel have had issues exactly what bwguardian posted. Oil on the maf sensor. Search youtube for exhaust leak and see if the sound you hear is simular. It could be the manifold gasket is leaking and your 02 sensors are picking that up and throwing a code.


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## davidluster (Sep 16, 2008)

Thanks for the replies. I have cleaned the MAF sensor again during lunch break. We will see what that does. That makes 3 times I have cleaned it. I searched on you tube and nothing is quite the same sound. I pulled the wheel well housing thing off and can feel air coming out of the very front of the exhaust manifold. it seems as if this is where the sound is coming from. The sound is MUCH MUCH worse when its cold and last longer. Last week it was lound and lasted a lot longer and the idle was very rough when it was real cold. today the idle is smooth and the sound last a second or two. almost gone by the time i cranked it and stuck my head under to listen.


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## TerryM (Apr 19, 2005)

Chase all the hoses that come off the PCV. One on my 5.4 Expedition goes to the very back side of the engine. Common to leak, almost have to go by feel. They crack, and open/close on vehicle movement/temp etc. Fine one day then leaking the next.


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## carryyourbooks (Feb 13, 2009)

if you have an exhaust leak, the oxygen sensors will read lean condition. if you have any other questions, call my bro at 281-755-7692. his name is sammy. he's been a ford mechanic for a looooooong time.


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## rebelangler (May 21, 2004)

the exhaust manifold wont make your truck run lean it is usually on the intake side of the process where that code comes from. your k&n air filter is most likely the cause of the issue. the time it takes for the cel to come back on after resetting the codes is usually how bad of a vacuum leak you would have. you can check by lightly spraying starting fluid around vacuum connections to find it. check the back of the motor first as this is where it usually is. when the starter fluid is sucked in by the leak the engine will rev slightly and theres the culprit. fix that and you should be good....talking from personal experience on this one from my 08 5.4..my cold air intake has caused my cel to come on and while searching that i found all this other info and tricks to narrow the search... good luck and keep us posted..

brian


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## Gfish (Aug 31, 2009)

I do agree that it might be the O2 sensor but I disagree the it your K & N filter. I put one on my 2007 F-150 and my gas milage has gone up and so has the power in the engine. I can feel the difference. My 1990 F-150 had an exhaust leak and when I finally got it fixed it ran a whole lot better.


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## davidluster (Sep 16, 2008)

I know that my K&N caused it to throw a code about 6 months after I first got it. There was a film on the MAF. I sprayed it with cleaner, reset my light and it stayed off for several months. I was thinking that maybe since my fuel filter was so dirty that maybe the injectors had gotten dirty as well and causing the lean condition. I guess I will see in time. I just reset the light yesterday and that is after a week and a half of giving it good gas+lucas. The truck has 220,000+ but still runs and looks pretty good.


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## j-haynie (Sep 5, 2008)

As stated above an exhaust leak will not cause a lean code. What type of cleaner are you using on the MAF. That could contaminate it and cause the codes. Spray around the engine with brake clean or some oxygen. Listen for the engine to change sound and or rpm. That is where your leak is from. If it takes a long time to come back on i would lean toward a leaking intake gasket. They are a rubber seal and will deteriorate after time. good luck keep us posted.


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## davidluster (Sep 16, 2008)

The cleaner I used was MAF cleaner...not sure of the brand. After i changed the filter I reset the CEL and it took several weeks to come back on. I am hoping it was just dirty/clogged injectors. I did the spray test with choke cleaner..assuming that would work as well. Didnt find any leaks that way. 

I got a length of garden hose and listened to what I thought was an exhaust leak....turns out is it is a pulley just in front of the manifold. I think it is a idler but I haven't had time to look closer.


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## j-haynie (Sep 5, 2008)

If it took that long to come back on i would think it is a small intake leak or the filter its self. Try a paper filter if the light comes back on. Give it a few weeks and see if it comes back on.


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## davidluster (Sep 16, 2008)

Will do! Thanks


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## j-haynie (Sep 5, 2008)

Did the paper filter fix it?


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## davidluster (Sep 16, 2008)

I didnt get a paper filter yet. I cleaned my K&N and filled up with good gas and dumped some lucas...light stayed off and ran like a champ....then the other day it got pretty cold and the light came back on immediately when i started it up that morning....now that i think of it the CEL came on the last cold snap we had. I know it sounds crazy..but I swear the cold weather is causing something to go wrong. It idles horrible in the morning if its cold outside. At lunch when it is warm outside it idles fine.....


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## j-haynie (Sep 5, 2008)

I bet you have intake gaskets leaking.


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## sam7 (May 25, 2010)

personally-k&n air filters aren't good for gas or diesel. fyi an exh leak can cause a lean code. most of the time it will set a rich code. the lean code is set because the o2 sensor is sensing too much oxygen!!!! do like rebelangler said and spray throttle body/carb cleaner around vacuum hose and intake gaskets and listen for a change in the way it runs. depending on your mileage, you may have a bad o2 sensor. i've never had 2 sensors go bad at one time unless you ran bad gas.


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## DSL_PWR (Jul 22, 2009)

Dump the k&n filter. It will ruin your motor. Just run stock, it is the best option.


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## sam7 (May 25, 2010)

another issue i've run across is the idle air control valve sticking when extreme temp change (hot or cold). if it sticks open too much this will let too much fresh air in the exh and cause a lean code


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