P0172 Code

[Robjs111]

Motech
Thanks for the info.
MAF checked out good.
I recently installed a 180 thermostat and coolant level is good.
Bronco starts great when cold or hot but after maybe 5 mins or so i press the accelerator and wait for rpm to drop to idle is when the issues start. Pulled another P0172 as well. Also bronco sounds great when i press the accelerator, main issues is bad idle when warm.
Thoughts.
Again thanks for the help..

 

[Motech]

As I wrote, determine if both banks are running rich. This is key. There is a huge shift in diagnostic strategies between one bank with corrupted fuel control and both.

Rich running is tracked by Fuel Trim values. With O% being perfect, positive% values represents the system adding fuel to compensate for lean running, and negative% values represent subtracting fuel to compensate for rich running.

Fuel control codes will set when total LT & ST fuel trim deviates +/- 18 to 20%. (My observations, not a spec)

Best way to answer the critical question of Bank 1 and Bank 2 fuel control equity is to check Freeze Frame data with your scan tool. Freeze frame is a data capture stored in memory the instant the code sets. It will include long-term fuel trim (LTFT) and short-term fuel trim (STFT) values for each Bank within that data.

(If you can't access Freeze Frame data, then live data is helpful too, but not as reliable for this purpose.

If Bank 2 fuel trim is -10% or lower, then both banks are corrupted.

If you cannot access FF Data, no biggie cuz live will do. But you can't properly diagnose corrupted fuel control without live data, period.

So then what?

Start with something you're positive could cause your issue, and correct that before anything else.

My first point would be your thermostat. Put the right temperature rated stat in there, probably 192-195°F, reset your PCM/KAM with a 20 minute battery disconnect and drive it. If your rich running code comes back, invest in a scan tool that provides live data.

 

[Motech]

CORRECTION:

My first check would actually be for anything causing MAF to exaggerate metered air flow (which would affect both banks).

Exaggerated metered air is unusual because it can only be affected by incoming air upstream of the MAF. That leaves only two realistic options:

1. Altered intake setup, like aftermarket air cleaner assemblies, and
2. Miscalibrated MAF sensor

Aftermarket air cleaner or MAF sensor (or both), would be the first itrms i would address.

Again, this would affect both banks, and this is why making that determination is so important. If only one bank is affected, I'm looking at plugged exhaust or faulty injector.

But when you consider it runs fine until it gets really warm, neither of those issues would be likely, so without data, it's not a reach to presume both banks are corrupted.

 

[L\Bronco]

Hey guys, thought I'd chime in with my 2 cents.
No MAP on those, However, The BARO reading can be used to identify a skewed MAF sensor. The BARO is calculated based on MAF readings plus a whole bunch of crazy calculations.
But, compare what the PCM thinks the barometric pressure is against what it actually is in your area. If the truck is wrong, its usually a skewed MAF sensor.
That being said, Motech is right, its unlikely a MAF or hi fuel pressure issue will only affect one side. P.S> bad HEGO grounds can create false rich as well. (But they are all grounded together.)
Could be a bad O2 sensor, Depending on how rusted they are, you could swap bank 1 and 2 sensors and re run KOER and see if your P0172 Changes to a P0175.
It's a bit of work, but no parts to pay for.
Hope that helps, Cheers

 

[Robjs111]

While doing some tests for vacuum leaks i pulled KN style air cleaner off while motor running and realized motor sounded much better. Cleaned filter but realized new intake air filter is needed. Cleaned mass air meter but now pulling codes of P0174b system to lean bank 2, P0133 slow response bank 1 sensor 1 and 1131. Bronco runs good and no cel light on but pulling codes from scantool. Since i posted i replaced vacuum canister and changed t stat from 185 to 195. Motor is new with maybe 50 miles on since install and i used original upper/lower intake with new injectors.
thanks

 

[Motech]

Oops. I forgot about plugged air filters as a rich running code cause.

 

[Robjs111]

Possible for motor to get to much air?

 

[Robjs111]

learning about how to use live data and found out STFT is showing lean condition and O2’s are under .45V.

 

[Robjs111]

Some more screenshots.

 

[Tiha]

You said the engine is new. Maybe it is still learning?

Otherwise lean on both banks is usually vacuum leak I thought.

 

[Motech]

Lots of data there, some of which can muddy the thought process. Example: STFT B1 S1 & STFT B2 S1 are deceptive. They are measuring immediate oxygen sensor trends and do not reflect fuel control the same way STFT does, and cannot be accurately used for fuel trim analysis. Best to disregard those bits.

I'll say this though: the Freeze Frame data is very contradictory. It is for Rich Fuel Control, Bank 1 P0172, yet both banks are reading high LTFTfuel trim values consistent with lean running. That is some kind of anomaly there worthy of a full Keep-Alive (KAM) Memory reset. This tool probably does not have that factory "Enhanced" feature. It can clear codes, but adaptive memory will not be reset, like LTFT for example.

Then there's the conflict of dueling banks, with one code for RH bank running rich, the other for LH bank too lean. I'd like to see the Freeze Frame data for that one too, but it is likely still "PENDING", and FF data is not captured until a pending code matures to a Check Engine light code.

So...

With the amount of conflicting data, I'd say that @Tiha is onto something with new engine break-in affect. With that, I'd make sure engine is fully broke in, all hoses and intake plumbing are righteous, all your fine tuning is done and it's pretty-much road ready. Then I'd reset KAM with a 20 minute battery disconnect to eliminate all learned fuel trim memory and drive it for a couple of cold start cycles in see what comes up.

Disregard those oxygen sensor trim numbers for now too, and if you can, convert your MAF values on the tool to metric Grams per Second (gm/s) instead of English (pounds per minute), it will be much easier to interpret.

 

[Robjs111]

As of now about 100 miles on motor since install.

I ran a smoke test and found several leaks on intake tube which is an aftermarket KN style. Also seemed to be a leak near Iac and tps. Not sure how tps could leak vacuum but i checked iac and all good. Going to devise a plate to cover TB opening so I can try a smoke test without TB and intake tube.

Possible that the O2 sensors are bad?? Not sure how old but bronco has 188k on clock.

When I removed tps to check for vacuum leaks I found that tsp was installed with pigtail pointing away from iac not towards.

I will remove + cable and reset computer.

 

[Motech]

I ran a smoke test and found several leaks on intake tube which is an aftermarket KN style

That alone could be your problem, especially at the leaks are in the metered air side. That is, the section of tubing between the MAF and the throttle body.

And congratulations on the absolute best approach: the everlovin' smoke machine! Absolute best tool for vacuum leak detection.

Also seemed to be a leak near Iac and tps. Not sure how tps

Yes, there will always be small leaks at IAC, throttle blade shafts and EGR. The PCM is calibrated to account for this.

Going to devise a plate to cover TB opening so I can try a smoke test without TB and intake tube.

Excellent plan. I always pop some plugs into TB openings to seal them up tight, then pull the hose off the PCV valve and inject your smoke directly into the PCV vacuum hose. You will eliminate crankcase and intake duct this way, smoking nothing but intake manifold.

At that point, if you get smoke coming from the crankcase, like out of the crankcase breather hose that connects to the intake air tubes for instance, for the dipstick tube, you know you have internal intake gasket leakage. Plenum gasket will sometimes leak internally. So can piston rings, but sometimes temporarily from a misfiring cylinder washed down with raw fuel.

Smoke is sometimes hard to spot shining a light directly at it. Especially LED. They are just too darned white to see the smoke unless you can get the light behind the smoke. But for these purposes, good old-fashioned filament style flashlight with a yellowed beam will work better than LED. Even better yet, a UV light if you can get a hold of one.

One final thing here. Miscalibrated MAF sensors can cause a lot of different and weird fuel trim issues. You might think it's a vacuum leak, but be chasing your tail because it's being caused by that aftermarket k&n setup.

And that would be the difference between an actual lean condition or a perceived lean condition, ie: a metering problem.

With Ford, you can look at barometric pressure data, or BARO frequency, and instantly determine if you've got a metering problem.

That won't do you any good with the generic scan tool, so the second best thing is to see where the fuel trim is the highest.

Generally speaking, vacuum leaks cause high fuel trim at idle whereas a metering problem will usually cause higher fuel trim at elevated engine speeds. It's not 100% either way though, it'll be a blend. What you want to look for is if your combined fuel trims--that is long-term and short-term added together--are higher at idle or 3500 RPM. If they clean up nicely at the higher speed, then it's going to be a vacuum leak. However, if they jump notably higher at high speed than they are at idle, then focus on your MAF and intake air plumbing.

Hope this helps.

 

[Motech]

One more universal test for a metering (MAF) lean condition you can perform with your generic scan tool if it will allow you to isolate just one data PID at a time.

Isolate the Calculated Load PID only, or Load as it may be called. Watching that data, rev the engine with a mash to the floor and off. Don't let it over rev, but let it get up there close to red line. While watching it. And be aggressive with it. Don't do it casually.

Do this multiple times to get a good picture of the maximum calculated load you're getting.

You should see it get up close to 90% or more. If it stays below 80%, especially if it's closer to 70%, then you do have a metering problem that needs to be addressed, likely a faulty MAF.