Running too lean
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Freshman User
Joined: Jun 2004
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From: Erie, PA
Running too lean
Hello,
My truck is running too lean, the check engine light because of it. Can anyone tell me what to check to correct the problem? And if I run it like it is, will it hurt it?
My truck is running too lean, the check engine light because of it. Can anyone tell me what to check to correct the problem? And if I run it like it is, will it hurt it?
Postmaster
Joined: Aug 2001
Posts: 4,532
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From: Trussville, Alabama
Patty,
Auto Zone can generally read the code and tell you what the OBD II is reporting as the problem.
Absent that, I believe I'd take it to Ford, or a trusted service shop, to read the code and tackle the problem.
Could be a bad O2 sensor, bad fuel injector, or something else.
Excessively lean conditions scare me.
Too rich and your not likely to cause any major damage.
Too lean and combustion chamber temps can get too high. Possible damage to piston and valves.
I wouldn't let it go unchecked.
Auto Zone can generally read the code and tell you what the OBD II is reporting as the problem.
Absent that, I believe I'd take it to Ford, or a trusted service shop, to read the code and tackle the problem.
Could be a bad O2 sensor, bad fuel injector, or something else.
Excessively lean conditions scare me.
Too rich and your not likely to cause any major damage.
Too lean and combustion chamber temps can get too high. Possible damage to piston and valves.
I wouldn't let it go unchecked.
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Freshman User
Joined: Jun 2004
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From: Erie, PA
Thr truck is in the garage now for state inspection. The prices are outrageous. I can do most of the work, but I just don't have time. They said that they wouldn't worry about the problem right now. They said it is running well, and it shouldn't hurt it. They said they ran the codes, and to go down through the checklist would cost about $70.00. I am going to check the fuel filter and such before I take it back for them to do that. If it overheats won't the gauge read that it is too hot? Get this, the garage is trying to charge me $86/per rotor. I called a local auto store and they are only $38.00 a piece. So I am going to take them up after work.
Postmaster
Joined: Aug 2001
Posts: 4,532
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From: Trussville, Alabama
Patty,
The temp gauge might not reflect a problem. If one cylinder runs hot, you'll have localized overheating. This could burn a valve but never really impact the temp seen by the temp sensor. The coolant could stay perfectly normal and you still have a problem internal to one cylinder.
Stay in touch.
The temp gauge might not reflect a problem. If one cylinder runs hot, you'll have localized overheating. This could burn a valve but never really impact the temp seen by the temp sensor. The coolant could stay perfectly normal and you still have a problem internal to one cylinder.
Stay in touch.
Junior User
Joined: Jan 2004
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I am encountering a similar problem. My codes all relate to the cylinder bank on the passenegr side. The code merely states that I am having "slow response, " whatever that means, ffrom the O2 sensor(s). My check engine light will come on, stay on for several on-off cycles, then it goes away. I was under the impression that this engine will keep the check engine light on until it is re-set; guess I am wrong.
I pulled all of the plugs on that bank and they were gapped properly and did not show evidence of a localized overheating condition.
Lemme know how yours turns out, Patty.
I pulled all of the plugs on that bank and they were gapped properly and did not show evidence of a localized overheating condition.
Lemme know how yours turns out, Patty.
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Freshman User
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From: Erie, PA
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Postmaster
Joined: Aug 2001
Posts: 4,532
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From: Trussville, Alabama
Patty,
Find the "search" feature and do a search on "lean" in the 4.2 forum. There have been several threads here in the past on lean conditions. Maybe somethign in on eof those threads will help you out.
You mentioned "they" said not to worry about it. It is running well.
That confuses me. From what I understand:
a) your CEL came on.
b) you got someone(?) to read the code and tell you it is running lean.
c) "they" told you not to worry about it.
What other information did they give you about the code?
One cylinder bank? Both banks?
We'll try to help if you need us (but no guarantees
)
here is a link to codes and what they mean:
https://www.ford-trucks.com/articles/2004/29.php
Find the "search" feature and do a search on "lean" in the 4.2 forum. There have been several threads here in the past on lean conditions. Maybe somethign in on eof those threads will help you out.
You mentioned "they" said not to worry about it. It is running well.
That confuses me. From what I understand:
a) your CEL came on.
b) you got someone(?) to read the code and tell you it is running lean.
c) "they" told you not to worry about it.
What other information did they give you about the code?
One cylinder bank? Both banks?
We'll try to help if you need us (but no guarantees
)here is a link to codes and what they mean:
https://www.ford-trucks.com/articles/2004/29.php
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Freshman User
Joined: Jun 2004
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From: Erie, PA
After reading all the different threads I feel confident that one of the O2 sensors are bad. The garage where the truck is read the code, but they are giving me the run around because they want to fix it, and I won't let them. They want to charge me $70 to diagnose, and only god knows how much to fix the actual problem. I asked for the codes, and he didn't want to tell me. Finally he said there are 5 codes. I don't believe that there are 5 codes at once. Can this actually occur? I went to www.actron.com and the codes they gave me are contradicting themselves. One is saying it is running too lean, one too rich. The codes correspond with both banks. How can it run to lean and rich on the same bank. This makes me believe they are lying. All of the spark plugs were white which means it is running too lean all the way around. I told them to park it and I am coming to get it. I guess I will have to take it to Autozone to get the real reading. Can anyone tell me which bank is on which side?
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Too lean? Check this
Hi, I read your posts and have a couple suggestions. First, there is a 90 degree vacuum line nipple on the rear of the cylinder head. Because of engine heat, this nipple is vulnerable to splitting or cracking, which will cause a lean condition. About a year ago my '98 was showing lean codes on both banks, and even though the truck still ran fine, gas mileage was horrible. I replaced all 4 oxy sensors to no avail. Then one day I noticed a slight 'hiss' coming from the firewall area, which I was able to trace. A new vacuum nipple from my friendly dealer solved the problem.
There is another 90 degree vacuum nipple under one of the front intake runners (near the throttle body). Just recently, this nipple split on me and I was getting lean AND rich codes, in addition to erratic warm idle and crappy gas mileage. Autozone suggested a new MAF sensor, which did me no good.
After discovering the air leak and replacing the nipple, I have had no further problems. Hope this helps.
There is another 90 degree vacuum nipple under one of the front intake runners (near the throttle body). Just recently, this nipple split on me and I was getting lean AND rich codes, in addition to erratic warm idle and crappy gas mileage. Autozone suggested a new MAF sensor, which did me no good.
After discovering the air leak and replacing the nipple, I have had no further problems. Hope this helps.
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Patty, in response to your questions, yes it is possible to have 5 (or more) codes stored in your computer. Mine had 8(!), lean AND rich(!) as mentioned in my previous post. As to which side is which, "Bank 1" refers to the side that number 1 cylinder is on; on the 4.2 engine it is the passenger side. Make sure you or your mechanic checks for vacuum leaks before you start replacing oxy sensors. Good luck, Andy
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Freshman User
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From: Erie, PA
Thank you Big 6. I got the truck from the mechanic, and took it to Autozone. Only two codes came up, and it said both banks were running lean. The guy at Autozone said it could of just been bad gas, or needed spark plugs. Since I already changed the spark plugs he reset the light, and said wait until it comes back on to pursue anything. We had a epidemic here with bad gas that was ruining gas gauges, due to having too much sulfur. Almost every gas station had this gas because they all get it from the same refinery. It was mainly affecting GM cars. I have a Corvette, and it got affected by it also. The light was reset 4 days ago, and still hasn't came back on, so I hope the problem is solved. I have probably driven it for about 50 miles or so since then. Lets keep our fingers crossed.
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You're welcome, Patty. If both banks are lean I still say you have a vacuum leak somewhere, unrelated to bad gas or spark plugs. If the light comes on again check those connections, it's a simple fix and mine went bad at only 100k miles.
Cargo Master
Joined: Aug 2002
Posts: 2,013
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From: Cajun Country
Big6,you are correct.I have had to fix a few of my friends F150s and 1 E150 for this same problem.You can get the pcv kit(pcv valve,plastic tube,rubber 90*,and misc vacuum hoses)from your local Ford dealer for $18.00-$25.00. 
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