long term fuel trim bank 1 and 2 are high but not high enough to set a code.

[mxl4729]

i bought a 2008 ford ranger 3.0 with 90K miles a few years ago.

the truck ran ok but seems to run a little rough at idle and lacks power but that my just be because it has the 3.0

well when running the code scanner the long term fuel trim in bank 1 and 2 are high at idle. Bank 1 is around 15.6% and bank two is 17.9%

when the truck is under load close to flooring it 96% load the long term fuel trim drops to around bank 1 9.3% and bank 2 10.1%

short term fuel trims seem to hover around 0 like it should all the time.

these high long term fuel trims made me thing i had a vacuum leak and or bad MAFS. I cleaned the MAFS and then replaced it with no change in LTFT. next i did a smoke test and the only place i had any smoke was the EGR valve. i replaced it and the new one seems to smoke the same amount so i don't think that's the source of my leak.

I checked my fuel pressure that that seemed good as well. I am kind of stumped. i would think under load at high RPM the LTFT would drop more then 7% or so but i don't know what it should be doing.

Based on the attached graph and the info above would you agree i have a small vacuum leak?

anyone have any ideas that i should be checking on the 3.0?


image below is no load at idle

Image below is almost full load

,,,

 

[RonD]

Welcome to TRS

LTFT(long term fuel trim) is part of STFT(short term fuel trim)

The computer is programmed for size of the engine, size of the injectors, and the expected fuel pressure, these are things that can not be changed

So at any RPM and throttle position the computer will know exactly how much air is coming into your 3 LITER engine, its just math
What it doesn't know is the WEIGHT of that air, that's what MAF sensor and Air Temp sensors are for, these help computer calculate the WEIGHT of the incoming air

Thats needed because gasoline 14.7:1 air:fuel Ratio is a WEIGHT RATIO, not volume
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline

A liter of air weighs more at sea level than at 5,000ft elevation, its also pressure related but still WEIGHS more, lol
A liter of cold air weighs more than a liter of warm air, that's how Hot Air Balloons work, the warmer air inside the balloon floats above the heavier cooler air on the outside of the balloon

Gasoline tends to always weigh the same cold or warm, changes just a bit

Vacuum leak causes MAF to not "see" all the air, so weight it reports is lighter that it should be

Computer calculates the OPEN TIME for each injector based on the 14.7:1 ratio
It knows a 14lb injector can flow 14 pounds of gasoline per hour at 60psi pushing it out
That's why fuel injectors are all rated in Pounds Per Hour, just FYI

That calculation is STFT 0, but.............computer then ADDS LTFT to that and thats the STFT 0 that you see
So if your LTFT is +15 and STFT is 0 then your really running at STFT +15

Thats the point of LTFT, so the computer doesn't have to reLearn fuel trims from scratch every time you start the engine
Its also needed on Cold Starts when no O2 sensors can be used
So LTFT allows the system to Age gracefully, small vacuum leaks, lower fuel pressure, small issues

If you find the vacuum leak or another issue then what you will see is STFT showing more negative numbers, like -5 to -10
And that will slowly bring down LTFT over time

Now STFT and LTFT are ALL based on O2 sensor data, all 3 or 4 are used

O2 sensors last 12 years and they start to show FALSE lean, no codes, just causes engine to run Richer than it should so MPG slowly drops costing you $$$ every time you fill up
So if O2s are over 12 years old, change them, its FREE in the gasoline you will save over the next 12 years
And it could bring your LTFT down

 

[mxl4729]

RonD ,

Thanks for the reply and this is good information.

i will jack the truck up tomorrow and see if all the O2 sensors look original.

This is the first time i have seen the around 12 year life for an O2 sensor. I though when they age they get sluggish and just take longer to respond.

when O2 sensors start to fail and read rich or lean is the failure somewhat linear? the drop in LTFT at load is what what made me think vacuum leak.

is there any other way i should be testing the O2 sensors on this ranger or is it not worth the time and i should just replace them?

someone had replaced one of the CAT at one time on this truck. not sure why it was done before i got it. my though was the small vacuum leak caused the engine to introduce more fuel overheating the CAT and causing it to fail

I though the downstream O2 sensors were just used for emissions and had a very small impact on LTFT. Is it worth the time and money to replace them?

 

[RonD]

O2s use a chemical coating to detect Oxygen in the exhaust, and coating just gets used up, recommended change time is 100k miles or 10 years, I use 12 years as the drop dead point, lol

O2s are actually the ONLY sensors that wear out, get used up
My 1994 4.0l has all original sensors, except for O2s, knock on wood

 

[mxl4729]

So i replaced both upstream O2 sensors.

Bank 1 did not want to come out and when i did get it out it lost some threads. Needed to take the plastic off and i still could not get an O2 thread chaser in still. had to go to harbor freight and get a tap set so run an 18mm 1.5 tap through it to get the new o2 sensor in.

well the job is done and there was no real change in the long term and short term fuel trim. I drove around for 20 mins and then took this picture. so I do believe I am getting an accurate STFT reading now. I did not change the rear O2 sensors yet but i figured the 1 sensor would have some affect if that was the issue causing these numbers to be high.

 

[RonD]

Both upstream sensors look to be more negative average

Change rear O2 as well, plays a bigger roll in LTFT because computer has to feed the Cats more fuel to keep them HOT, which would be a False lean from rear O2

Rear O2(s) should run with steady higher voltage, 0.7 to 0.8 volt, so "rich" but not what it means, lol
Higher voltage from O2 means less Oxygen because that's all O2's can "see", Oxygen
Cats should burn up most of the Oxygen in the exhaust while burning up pollutants, so low oxygen high volts and steady voltage from rear O2(s)

 

[mxl4729]

interesting i guess i will change them as well.

when i was putting everything back together i found two interesting things.

on the drivers side my exhaust manifold is cracked starting by the EGR tube.
you can see in the picture and it seems to be leaking although it hard to tell. when i just started it my though was i could put a little soapy water on it and it would bubble but it just evaporated very quickly. not sure if maybe oil would work better?

then i looked at the other side and the head or nut of the last bolt of the exhaust manifold on the passenger side is missing. see images below.

you think the crack on the drivers side and the bolt missing on the passenger side would cause enough of a leak on each side to drive up the LTFT?

anyone have any idea how to fix these with out pulling both exhaust manifolds? I have removed them before on other vehicles and it was a nightmare.

 

[RonD]

Yes, you will need to deal with the nightmare

Good find, well as far as what may be an issue, not good because it needs to be repaired

Leaking exhaust is not really an issue for engine computer or engine running, but................
What IS an issue is that AIR is sucked in if the leak is in the exhaust manifold before O2 sensors, and as we know O2s see AIR(oxygen) so that air causes O2's to show False Lean
Also all vehicles after 1970 or so have tuned exhausts, scavenged power, this means at certain RPMs the exhaust manifold has Negative Pressure inside to suck out exhaust, if there is a leak it sucks in AIR as well
But air is still sucked the rest of the time through a leak, just not as much


JB Weld ExtremeHeat version, works on cracks in exhaust manifolds, you can try that on the one side
Also price out a replacement manifold for the other side

Missing bolt side needs to come off and the broken bolt removed and new bolt installed

Check with exhaust shops to see how much they would charge to do that one side
They know all the tricks to get off/out rusted and/or broken exhaust bolts, and have all the tools and replacement bolts on-hand
What might take you 3 hours they can do in 20min

If its reasonable you may want them to do the other side with replacement manifold at the same time
I would replace the EGR pipe as well

 

[mxl4729]

Any idea what the heads are made out of? Aluminum or steel/iron for the 3.0 2008 ranger. I have a MIG welder and have used it to remove broken studs before but only in aluminum.

 

[RonD]

Cast iron heads and block on the 3.0l Vulcan

 

[mc17eln]

@mxl4729 When I did the engine rebuild, I installed the block and heads without the exhaust manifold. There are plenty of space on both sides. I also had 3 broken bolts on the old heads, but they were fairly easy to remove with just a pair of channel lock pliers and lots of PB Blaster. It may be a bit challenging for you with the cylinder heads still on the block, especially the lower 3, but not impossible.

For your crack manifold, I suggest getting one/pair from your local junk yard. Use anti-seize on all exhaust bolts.

 

[mxl4729]

@mxl4729 When I did the engine rebuild, I installed the block and heads without the exhaust manifold. There are plenty of space on both sides. I also had 3 broken bolts on the old heads, but they were fairly easy to remove with just a pair of channel lock pliers and lots of PB Blaster. It may be a bit challenging for you with the cylinder heads still on the block, especially the lower 3, but not impossible.

For your crack manifold, I suggest getting one/pair from your local junk yard. Use anti-seize on all exhaust bolts.

where did you get replacement bolts? and does the exhaust manifold on the 3.0 have a gasket?

my plan was to go check out the local junk yard that is pull your own parts and see if i can find a 3.0 motor. I know they have rangers as i have gotten parts before just not sure about if they have a 3.0

my the passenger side i was thinking about pulling off the wheel and plastics and seeing if i can get the drill or mig welder in to the bolt. since the bolt is broken flush with with the manifold i was thinking if i could fit a drill i could try a reverse thread drill bit and maybe it would come out. I have superglued a washer and then welded though the hole before then welded on a nut and had good luck removing broken bolts but it was always into an AL head. or try an easyout. i just hate to try and remove that exhaust manifold and snap a bunch more bolts

 

[RonD]

Yes, there are exhaust gaskets on the manifold
And you need to remove the manifold not just get the broken bolt out, because the gasket will already be damaged from leaking
So just replacing bolt wouldn't work on its own

Stop by an exhaust shop, independent shops are best, not chains, and ask the price, $50-$60 including parts(gasket and bolts) depending on your areas hourly labor

 

[mc17eln]

where did you get replacement bolts?

@mxl4729 I got a set of used bolts from the yard, then clean and select one out of two sets based on visual inspections. You found broken bolts, because people over torque them. The following are instructions from Ford workshop manual. The torque specs are VERY low:

Install the exhaust manifold gasket, exhaust manifold, bolts and stud bolts.

• Tighten in the sequence shown in 2 stages:
• Stage 1: Tighten to 10 Nm (89 lb-in).
• Stage 2: Tighten to 23 Nm (17 lb-ft).

Similarly, don't over torque plugs, as the manual says:

• Spark plugs: 15 Nm (11 lb-ft).

Use your 1/4 torque wrench, not the 3/8 nor your muscle. 17 lb-ft is 204 lb-inch, 11 lb-ft is 132 lb-inch. Buy new gaskets.

 

[mxl4729]

Does anyone know what years the 3.0 exhaust manifold is the same as 2008? I am going to the junk yard tomorrow and I know they have a 2003 and was wondering if that will fit. Would be nice to pick from a few so a range of years would be helpful.