[RocktimusPryme]

Lots of ex or current mechanics on the board. My beater pickup has been throwing a Bank 1 lean code. Google leads me to believe this is a common issue and one easy to fix. Usually a vacuum leak or dirty egr or MAF.

Well I read some tutorials on how to diagnose the specific issue with your scan tool by reading fuel trims. Problem is mine doesn’t seem to follow any of the troubleshooting trees.

More to the point, I noticed my long ft 1 is stuck at 29.7, I assume that’s max, and doesn’t move. All the other trims are constantly variable in a small range. Would this indicate a sensor not reading somewhere?

Or is this indicative of something like the MAF reading wrong, saying there is more air than there is and the engine trying to compensate?

[GpFreak]

MAF would affect both banks... what condition are your spark plugs?

[RocktimusPryme]

Originally Posted by GpFreak

MAF would affect both banks... what condition are your spark plugs?

Makes sense, that would go for an actual fuel issue too though right? Like a filter clogged or a pump going bad. Save for maybe an injector on one side.

I read that the lean bank 1 is often the PCV valve leaking into it. But I sprayed a can of ether all up and down the lines and near the intake, it never revved up any. So if there is a vacuum leak somewhere I dont know where.

[HO 67 BIRD]

Can you read or see the o2 sensors readings with your scanner. Might be a bad o2 sensor on bank 1.

[RocktimusPryme]

Idk, maybe, its got a bunch of acynyms that I dont immediately know what they are.

[n2ogpsj462]

'LT' or long term fuel trim is how the motor is running. Short trim is what the computer is trying to do to correct the issue. The goal is zero so if the motor is seeing a long term trim of '5' that's lean so the short trim will go to -5 because it's trying to fatten it up. I'm not sure if 29 is the max. It may have frozen adapts after throwing the code. What's the short trim for bank one? Clearing the code will start the LT back at zero. How long til it gets back to 29? What are the readings on bank 2?

[mgarblik]

I can help get you started at least. First, the problem is very unlikely the MAF sensor, because as mentioned above, that would effect bank 1 and bank 2. A fouled spark plug is possible but probably would have a P0300-P0308 codes with it. As mentioned, it would be great to have a look at the O2 sensor voltages. I think your truck would have 4 oxygen sensors. The acronyms would be HO2S Bank 1 sensor 1, Bank 1 sensor 2, Bank 2 sensor 1 and Bank 2 sensor 2. Different scan tools call them out differently. Look for something like HO2SB1S1 , or O2B1S1. Something like that. When you find that data, the front O2 sensors should act basically the same. Both should fluctuate up and down in voltage rapidly indicating lots of activity. If the voltage is high, low, or steady, that's bad. On a Ford V-8, Bank 1 is the passenger side because that's where the #1 cylinder is. So the right side is giving the computer a lean running indication. In response, the computer is pouring extra fuel into that bank. This lean condition can be FALSE. ANY EXHAUST LEAK from the manifold to the location of that O2 sensor can really mess with the O2 sensor by letting oxygen enter the exhaust stream. If I was working on this truck based on what you have posted, I would verify no exhaust leaks and them verify the proper operation of the 2 front O2 sensors. The rear O2 sensors are not important in your diagnosis at this point, so don't worry about them right now. Hope this gets you started.

[RocktimusPryme]

It will come down if I bring the engine to like 2500 RPM. Ill go out and take some pictures.

[mgarblik]

When you say come down, are you talking about the fuel trim? If so, that is typical of an exhaust leak effecting the O2 sensor. At idle, a tiny amount of oxygen enters the exhaust stream because there is little exhaust in the pipe. At higher RPM's it has less effect. Also, the fuel trim has specific trim cells. Probably on a vehicle like a 2001, 16 or 32 trim cells. They are based on load and RPM. Just for fun, put the truck in drive, rather than park, see what the trim does. Or lightly power brake the truck and see what the trim does.

[RocktimusPryme]

Here, https://www.youtube.com/watch?v=dUYUR2gUvlw just make everyones lives easier.

O2 sensors seems to be okay, both fluctuate in similar fashion.

[Half-Inch Stud]

Ohm out the coil packs for 5000-6000 ohms to assure the secondary windings didn't fry open.

BTW I use Ford truck coil packs (towards 5000 ohms) on my 95 lincoln (instead of 5800-6000 ohms) along with a reduced plug gap. Result is a defnite improvement in jack-rabbit pedal response.

Also cut & blended the MAF to remove the airfoil divider (simply not needed) easire to cut out the plastic MAF hsy then the aluminum, but i've done both. Improves highway passing HP a bunch.

[Half-Inch Stud]

I think the valveseals fall away at 100,000-120,000 like clockwork and make the EGR a maintenance crusty-cleanout activity.

Present 95 Lincoln is clean at 114,000 mi and....will need vavlve seals soon.

[gtohurstjudge]

I've been in the car repair business for 42 years.........You don't state
what engine is in your truck. If it is a v-6, you have a clogged fuel filter or leaking
intake gaskets. If you have a 4.6 or 5.4 liter v-8, you have a clogged fuel filter or
a leaking pcv hose where the giant rubber nipple attaches to the intake manifold. It sucks a hole in itself on the bottom side where you can't see it. You
need to completely remove the pcv hose and inspect this nipple. That's what lean codes are on the v-8's of that year model 90 percent of the time. If all these
things check out to be OK, it's time to have the intake put on a smoke machine
to look for smoke coming out somewhere. On the v-6's the intake gaskets are rubber o-rings and they shrink and cause lean codes and usually a smoke machine won't show the leak.

[TedRamAirII]

If the LT Fuel Trims comedown at 2500 rpm, you have a vacuum leak affecting bank 1 (right side) Check the hose leading from the intake manifold to the valve cover pcv valve. Usually at the rear of the intake, in back of the throttle body. If thats ok, check all vacuum hoses.

[mgarblik]

Thanks for the video. If possible, could you make another one about 3-4 minutes long? Just not enough time to watch carefully the operation of the front. o2's. If you say they are trending up and down and essentially acting the same, then having one fuel trim maxed out and the other normal is a bit more of a mystery. The Front O2 sensors are essentially the monitor of the fuel trim. If the O2 sensor is giving normal data and the fuel trim is maxed out, the next thing to do is to reset the fuel trims to zero and once again watch the 2 front O2 sensors. If there is a problem with the right bank actually running lean, with the fuel trims re-set, the right O2 sensor should read low voltage mostly until the fuel trim climbs up again and compensates. If it does in fact act that way, then you have verified an actual lean condition on the right side of the engine. Now you would have to fix that. First thing to look for is a vacuum line or some vacuum leak that is specifically on the right side of the intake. Next, possibly one of the injectors is partially clogged and not injecting enough fuel at idle/low speeds. How does the truck actually run? Any miss or driveability problem? Especially at low speeds? I don't think you mentioned the mileage on the engine. High carbon built-up on the back of the intake valves can act like a sponge and absorb the fuel at idle and low rpm's. This can also create a lean condition. Generally not only on one side unless you have a failed valve seal letting carbon build more on specific valves. If the truck uses some oil or has high mileage, a 50/50 mixture of Seafoam or some other de-carbonizing chemical and water can be drawn through a vacuum port in the intake to clean the valves and top of the combustion chambers. Have the engine hot and maintain 2500-3000 RPM during the cleaning process. Good luck.

[RocktimusPryme]

Sorry, its a 2wd 5.4 liter. Pretty sure its the 2 valve version.

Anyway, thanks for all the responses. I think tomorrow I will just replace that PCV hose. Maybe that elbow mentioned too if I can find one. That does seem to be what it is most of the time as mentioned. I just figured when I sprayed ether around it you would hear the engine increase in RPM and it didnt.

[mgarblik]

Originally Posted by gtohurstjudge

I've been in the car repair business for 42 years.........You don't state
what engine is in your truck. If it is a v-6, you have a clogged fuel filter or leaking
intake gaskets. If you have a 4.6 or 5.4 liter v-8, you have a clogged fuel filter or
a leaking pcv hose where the giant rubber nipple attaches to the intake manifold. It sucks a hole in itself on the bottom side where you can't see it. You
need to completely remove the pcv hose and inspect this nipple. That's what lean codes are on the v-8's of that year model 90 percent of the time. If all these
things check out to be OK, it's time to have the intake put on a smoke machine
to look for smoke coming out somewhere. On the v-6's the intake gaskets are rubber o-rings and they shrink and cause lean codes and usually a smoke machine won't show the leak.

If you have access to a smoke machine, that could verify the vac. leak for you. PCV hose sounds like an excellent place to check. Also, any other vac. lines as mentioned. Not quite sure how a fuel filter would effect only one bank, but it's a good maintenance item either way. Let us know what you find.

[Half-Inch Stud]

Originally Posted by gtohurstjudge

I've been in the car repair business for 42 years.........You don't state
what engine is in your truck. If it is a v-6, you have a clogged fuel filter or leaking
intake gaskets. If you have a 4.6 or 5.4 liter v-8, you have a clogged fuel filter or
a leaking pcv hose where the giant rubber nipple attaches to the intake manifold. It sucks a hole in itself on the bottom side where you can't see it. You
need to completely remove the pcv hose and inspect this nipple. That's what lean codes are on the v-8's of that year model 90 percent of the time. If all these
things check out to be OK, it's time to have the intake put on a smoke machine
to look for smoke coming out somewhere. On the v-6's the intake gaskets are rubber o-rings and they shrink and cause lean codes and usually a smoke machine won't show the leak.

The better answer, compared to my guessing.

[chevymad]

Was going to tell you about that pcv elbow myself as well. When you see how big the hole can be you wonder how in the hell you could have missed it. That's my best educated guess anyway.