2001 GT code p0174

Hi, sorry to hear..
. This just occur one day, or get worse with time? Any work recently done?
Bank 2, lean. Likely a vacuum leak.
May also be a dirty MAF, bad fuel pressure regulator, clogged fuel filter, weak pump.
Try these, first....
Have a good OND-2 Scantool? If so-view your 02’ sensors while running closed loop, (should be cycling back and forth, not pegged in one direction or another). View your fuel trim.(Always correcting).
1) Low/high fuel pressure, what’s your pressure at the rail?
2) Inspect/pull a little vacuum on your fuel pressure regulator line by mouth for raw fuel inside, check line is free of defects, and
verify it’s tight.
Check your plugs for a strong spark,
4) Look for any vacuum leaks. Even a very small vacuum leak can cause drivability issues.. Inspect all your vacuum lines for damage, loose connections, etc.
Other vacuum related hoses (PCV, breather, evaporative purge).
6) Check your MAF sensor, should be at < 1DCV at idle, and make sure your wiring is solid.
7) If your PCV valve is old, replace it. Use the correct one. As the PCV system is basically a controlled vacuum leak, it needs to be correct. The “shake test” proves nada.
8) Check the throttle return spring tension. The TB must operate freely and close completely, Carbon buildup can also affect this, clean everything up to /including the throttle body/air filter, All your connections will now be 100% tight, clean MAF, TB, Filter.
Use CRC MAF cleaner on your MAF, can blast out the TB as well, a can lasts a long time & wont leave a film on your MAF elements.
Check that when the throttle is closed, it's resting on the idle stop screw. Very
important that the throttle returns to the same position every time when closed.

2 types of Idle Air Controllers (IAC). One has a black atmospheric vent. The other does not.

IAC with black vent: Usually seen on older Mustangs (early 2001& prior). The vent supplies bypass air to allow the motor to start. It contains a number of springs and diaphragms. The vent must internally close off when the engine is running. Not a service friendly part, internally.
Late 2001 & 2002+non vented IAC’s, can be cleaned. Be advised, that cleaning may not fix the problem or it may only work for a short period of time.
Is this when cold/warm or both?
Expect idle problems if the wrong IAC value has been used for the application.

Theidle strategy relies on the bypass idle air being supplied by the IAC. The throttle body butterfly valve is designed to allow only a very small (if any) air to pass.
Bad idea to adjust the TB set screw for low idle concerns. It may appear to work but when the weather gets cold, a high idle will result. Only gets you by temporarily.

A bad IAC may even cause a no start condition.
Start and allow the motor to idle. Disconnect the IAC electrical connector. The RPM’s should drop (black vent) or the motor should die out right (non-vent).

If the idle does not drop as expected then:
• The IAC is bad or dirty.
• There is a vacuum leak downstream of the IAC.
• The evaporative purge value (VMV) is stuck open. This is allowing excess air to enter via the charcoal canister.
• The throttle body butterfly valve is allowing too much air to bypass.
• The throttle body linkage is loose or worn allowing air to enter.
• The Throttle Position Sensor (TPS) is loose, bad, or noisy (not giving good closed throttle indication).
• The electrical connection to the IAC is open or shorted. Inspect the wiring. Pay special attention on boosted/modified applications that often need wiring.extensions.
-Alternator needs a solid 13.4-13.8V output to the battery, battery needs a solid 12VDC or idle issues will occur.
If you have that Scantool, monitor the IAC duty cycle (percent). It should change as the calculated load changes as parasitic losses like below are added
. Turn on the AC and head lights. Verify the IAC duty cycle changes in response to changing load. Also monitor the TP-MODE PID and see if it reads "closed" when the throttle is actually closed.
If the IAC duty % is very low (< 20), suspect TB set screw allowing too much air or a vacuum leak.
Try those, best of luck!
-John

With this code, shoot for exhaust leak first and foremost. It turned out to be this every single time for me. I chased thing after thing (mafs, iacs, tps, tb, you name it). There was a exhaust leak under the car dead center. It might be ever so small, spray some soap bubbles around with a bright high powered light with it running.

Hi,
Your fuel pressure has an adjustable fuel pressure regulator- correct? 53.5lbs is high, should be set at about 38lbs. As it’s running lean on that side, I’m thinking the 02 sensor is sending some erroneous info that’s not actually correct, and as Shuttleman83 posted, it’s quite possible due to excess air being pulled in via exhaust leak up front, this may trick the 02 sensor into thinking your mixture is lean, and the EEC responds by fattening up the mixture, causing erratic idle, and may explain the raw fuel odor.
Look at your exhaust system (up front), may be a header/exhaust manifold leak, a leak where the manifold connects to the exhaust piping, a weld crack in the piping, may even be the 02 sensor not sealing correctly. Also make certain your plugs are tight, another area that may pull unmetered air into the system. Pull your plugs and compare them, clean and regap. Read the plugs for differences, identify what colors indicate what (many charts online showing what plugs are telling you, Manual for your Car will have a decent chart on this.
Look closely with a flashlight, you may see black carbon tracking around an exhaust leak. Carefully propping the car up securely with a jack & stands with the Ebrake tight will make it much easier to locate, engine started & cold, you should be able to hear or feel it.
The exhaust running down the pipe creates a vacuum as it’s moving by, any vulnerable spot will pull air into the exhaust stream.
A 17.6% TPS reading at idle is excessive, what is the calculated load (%) the Scantool is reading at? The TPS reading indicated the throttle is open 17.6% of 100% (WOT) when idling, almost 1/4 pedal, I’d check your TPS and be sure it’s adjusted below 1DCV when the TB is closed. If you have an aftermarket throttle body, there is a specific method to set it, this should be performed. Not likely the only issue, but will help the effort.
Is this motor running an aftermarket tune, or is it running an aftermarket Throttle body?
Can you list the mods the motor has?
Hook up a vacuum gauge to measure engine vacuum while the engine is running.
If a vacuum leak exists i’d start first suspecting the left side of the motor. Note vacuum leaks may be created from sources such as:
Loose, unseated Spark plugs
Fuel injector O-rings
valve cover gaskets
EGR valve
Intake manifold on the left side.Engine cold, use a torque wrench so pure certain the bolts are to factory spec’s, using the proper torque sequence called out by Ford. Any air introduced beyond the MAF sensor can wreak havoc on idle and drivability.
The way you described the fuel trim suggests the EEC attempting to correct the mixture. Note the 02 sensors are not utilized when the motor is cold, they begin to work when the engine enters closed loop.
Try disconnecting your MAF as the engine is running, it should run awful or may stall. If this occurs, it’s likely it’s functioning as intended.
Compare the LTFT between bank 1 and 2. Compare the O2 voltage between bank 1 and 2. Do they switch? 02’s should continually be changing- even at idle when warm.
Additionally, look at the live data for fuel system one when the motor is approaching warm and it should say “CL” or “Closed”, indicating the car is running Closed loop.
A very simple cause that’s overlooked with issues such as yours is running coolant that isn’t topped off. This may cause the engine’s CTS to read air and not solid coolant temperature, air temp or bubbly coolant may not reflect actual coolant temperature, preventing or causing the engine from remaining in closed loop.
You may find an issue here, at worst, you’ll eliminate components, systems. Be sure to write down what you tested, and numerical values associated with the same for future reference. Solid values need to be jotted down, DONT want to backtrack unless your doing comparisons. Hard to recall exact values. Have any other codes that popped up in the past?
Since this has been an issue for a while, can you trace it back to anything changed when it began? (Why I mentioned importance of documenting things).
Good luck!
Best!
John.

Black GT said:

I have had O2 sensor codes pop up randomly since I have owned the car. The CEL will come on and read as a o2 code. Most of the time after a day or 2 they will clear themselves without using the scanner to erase them. The guy I bought the car from said he thought it had a tune on it but I don't think it does because it has a stock throttle body with the horse on it. I never thought much of the codes and attributed them to the H pipe. All the modifications were done before I bought the car. As mentioned it has a H pipe and straight pipped with stock manifolds. It also has a true cold air intake. Has MSD COP also. The fuel injectors are stock. I also recently replaced the ECT sensor as it threw a code and was reading -40 degrees. When checking live data today it was reading 203 degrees with the engine hot so I think it is OK. All the engine wiring and hoses appear to be in exceptionally good shape. The car is a manual if that makes a difference. I will try and find the time to get it up in the air tomorrow and check for exhaust leaks and run some more test. Will post what I find. Will also monitor voltage at the o2 sensors. From what I recall from doing live data today once the engine got hot o2's were flat lining. Voltage was not changing. I will get another reading on them Tomorrow. Can not thank everyone enough for the help. I really appreciate it. I miss driving my mustang.

Click to expand...

Hi,
I can Identity,, not driving your Pony is ifrustrating. What other codes have you seen in the past? Do you have a pic of the engine department to post
Whether modded NA, forced induction, or bone stock, all 0BD-0,1,or 2’s CPU program’s can be modified for improved performance.
You can gain 50HP+ tuning a stock 5.0 HO Mustang ang, or more with a cool air intake & modded exhaust- more. You’ll get better throttle response, drivability, and Want a baseline HP/TW reading?,
use G force to 60 MPH, easily calculated into gross & net numbers. Any smartphone will have the App. The tunand some bolt-ones, including 24lb injectors, MAF, 300HP is achievable . Injectors you must size up to #24’s- (good for 325HP).where your stock ones are good-for 260HP, which that motor is seeing stock. This may be why the
IIf I were giving one advice with money burning a hole in their differential gears to 4.10’s. Best bang for the buck
.


injectors are good .
#19’s are pretty maxed out at the 260HP the bar made, bone stock-2+

has been coaxed out of them.
You can buy a handheld SCT and have free custom tunes every time you make a modification- unlimited tunes, for free. long as you own it.Ask me about tuning options.
Best bet & the most popular so far is to buy a Holley Terminator X kit. It replaces your stock EEC, and will actually self program. Comes with a simple harness, and you can alter any parameter,, it won’t let you make dangerous adjustments, comes with a remote touchscreen & a Wizard that explains things as you adjust them. No prior Tuning experience, install is plug & play simple. Check it out!(you tube).
Ford tuned the 5.0’s gently from the
& net numbers. Any smartphone will have the App..
Note: If a Battery gets low from sitting, it can corrupt a tune, and make it run awful.
You mentioned the car isn’t driven a lot, how old is the Gas in the Tank?
Dfuel pressure to 38Lns via Regulator?
stock #19ln are inivadive injectosv may have Flow stronger
I realize that this wasn’t installed by you, but just FYI, running modern high flow Catalytic converter(s) will cause no discernible HP/TQ losses while keeping combustion by products at bay.
Some eliminate the rear 02 sensors via programming, or add reluctors to the rear 02’s, “tricking” the EEC into believing Cat’s areperforming their function.

Some work, most don’t.
Front 02 sensors in 2004 and earlier vehicles are what the EEC relies upon for A/F adjusting ratio’s.
Your DTC is suggesting bank 2 is lean..
If the intake gasket on bank 2 side, or exhaust leak, an injector’s o-ring is leaking, those types of things may cause an overall lean condition.
Testing: Some throw codes, some don’t, some intermittent. If you have a flashing code while accelerating, it means a cylinder is misfiring due to a weak spark, dirty/bad plug, leaky or bad injector.

1) The O2 heaters are bad
2) There's a wiring issue to/from the O2 sensors.(sometimes they melt on exhaust).
3) Of course a bad sensor itself.
4) Exhaust leak before the front O2 sensors, including header/exh. manifold gaskets..
5) O2 sensors are located too far away from the Motor (not enough heat in the exhaust).
6) Leak on one side valve cover gasket.
7) Clogged fuel injector, bank #2.
8) Intermittent Coil
9) Leaky spark
10) Plug wire arcing, run the car in the dark, you’ll see it.
11) When there is a problem with a vehicle, History proves that aftermarket ignition components are theme most likely to fail. Are you also running an MSD box? Disconnect/bypass it if possible. Check Coils resistance with a VOM.Coils- correct?
Swap bank 1’s injector with bank 2’s, see if you get a code from bank 1. Then, it’s the 02 sensor for certain.
It’s common for some to get this, I’ll say it. Upstream sensor is the one closer to the beginning of the exhaust, the downstream- furthest from the motor.
Good luck, post any other questions Half asleep, hope some content helps, see what you find. ALL Dynotunes at minimal, give you a copy of the program so you can load it into your handheld, which they generally furnish for you.
Best!
John

Want a baseline HP/TW reading?, You can time and use G force to 60 MPH, easily calculated into gross & net numbers. Any smartphone will have the App.

IAC Gasket will do this also or IAC not being flush to plenum. Try ruffing up the surface of the iac with a scotch pad or basic spong rough side then reinstall. A Help! brand iac gasket is at advance auto for like $5 or less. Also, Motorcraft IAC only. I once bought two at local parts stores and both were instantly bad and unusable.

Hi,
Agree with the above, may cost a few more bucks, but the importance of buying genuine Ford parts cannot be overstated.
best of luck!
John

08GT500 said:

Hi,
I can Identity,, not driving your Pony is ifrustrating. What other codes have you seen in the past? Do you have a pic of the engine department to post
Whether modded NA, forced induction, or bone stock, all 0BD-0,1,or 2’s CPU program’s can be modified for improved performance.
You can gain 50HP+ tuning a stock 5.0 HO Mustang ang, or more with a cool air intake & modded exhaust- more. You’ll get better throttle response, drivability, and Want a baseline HP/TW reading?,
use G force to 60 MPH, easily calculated into gross & net numbers. Any smartphone will have the App. The tunand some bolt-ones, including 24lb injectors, MAF, 300HP is achievable . Injectors you must size up to #24’s- (good for 325HP).where your stock ones are good-for 260HP, which that motor is seeing stock. This may be why the
IIf I were giving one advice with money burning a hole in their differential gears to 4.10’s. Best bang for the buck
.


injectors are good .
#19’s are pretty maxed out at the 260HP the bar made, bone stock-2+

has been coaxed out of them.
You can buy a handheld SCT and have free custom tunes every time you make a modification- unlimited tunes, for free. long as you own it.Ask me about tuning options.
Best bet & the most popular so far is to buy a Holley Terminator X kit. It replaces your stock EEC, and will actually self program. Comes with a simple harness, and you can alter any parameter,, it won’t let you make dangerous adjustments, comes with a remote touchscreen & a Wizard that explains things as you adjust them. No prior Tuning experience, install is plug & play simple. Check it out!(you tube).
Ford tuned the 5.0’s gently from the
& net numbers. Any smartphone will have the App..
Note: If a Battery gets low from sitting, it can corrupt a tune, and make it run awful.
You mentioned the car isn’t driven a lot, how old is the Gas in the Tank?
Dfuel pressure to 38Lns via Regulator?
stock #19ln are inivadive injectosv may have Flow stronger

Consider the car’s running a tune. Stock HP is 260, the injector duty cycle should never exceed 85%, exactly 260HP. If someone desires to do this the Wrong way, they increase the fuel pressure to make the 19lb-260hp@85% duty cycle, it may help- but absolutely incorrect way to do it
That explains the 50+LB fuel pressure setting, should be 38lbs.
Keep this in mind, I’d bet this is the case.
IMO, Find your core current issue, as you’re doing,- then we’ll look at the chronic issue.
If readings are badly affected, we’ll need to address them now. Did the Seller have a handheld rogrammer tht came with ‘tis, r did he mention nothing you may find ore info if you call him bac & ask”Was there a handheld programmer you bought with this Car, SCT, BAMA,HP Tuners, Diablo, .
It may of had dynotuning, some sell a handheld with a copy of the stock program, and the new one
.Others:
When watching live data and in closed loop you see an upstream 02 sensor remain at one value (or “Peg”), more often or not it’s an indication of that 02 sensor being a failed component. Not running Cat’s on the H-pipe that's installed?​

I realize that this wasn’t installed by you, but just FYI, running modern high flow Catalytic converter(s) will cause no discernible HP/TQ losses while keeping combustion by products at bay.
Some eliminate the rear 02 sensors via programming, or add reluctors to the rear 02’s, “tricking” the EEC into believing Cat’s areperforming their function.

Some work, most don’t.
Front 02 sensors in 2004 and earlier vehicles are what the EEC relies upon for A/F adjusting ratio’s.
Your DTC is suggesting bank 2 is lean..
If the intake gasket on bank 2 side, or exhaust leak, an injector’s o-ring is leaking, those types of things may cause an overall lean condition.
Testing: Some throw codes, some don’t, some intermittent. If you have a flashing code while accelerating, it means a cylinder is misfiring due to a weak spark, dirty/bad plug, leaky or bad injector.

1) The O2 heaters are bad
2) There's a wiring issue to/from the O2 sensors.(sometimes they melt on exhaust).
3) Of course a bad sensor itself.
4) Exhaust leak before the front O2 sensors, including header/exh. manifold gaskets..
5) O2 sensors are located too far away from the Motor (not enough heat in the exhaust).
6) Leak on one side valve cover gasket.
7) Clogged fuel injector, bank #2.
8) Intermittent Coil
9) Leaky spark
10) Plug wire arcing, run the car in the dark, you’ll see it.
11) When there is a problem with a vehicle, History proves that aftermarket ignition components are theme most likely to fail. Are you also running an MSD box? Disconnect/bypass it if possible. Check Coils resistance with a VOM.Coils- correct?
Swap bank 1’s injector with bank 2’s, see if you get a code from bank 1. Then, it’s the 02 sensor for certain.
It’s common for some to get this, I’ll say it. Upstream sensor is the one closer to the beginning of the exhaust, the downstream- furthest from the motor.
Good luck, post any other questions Half asleep, hope some content helps, see what you find. ALL Dynotunes at minimal, give you a copy of the program so you can load it into your handheld, which they generally furnish for you.
Best!
John

Want a baseline HP/TW reading?, You can time and use G force to 60 MPH, easily calculated into gross & net numbers. Any smartphone will have the App.

Click to expand...

Hi,
Oops ie-Caught an error I’d posted. 15-20HP by tuning a stock car is reasonable, 50HP is possible, just needs some solid bolt-in’s to get there is all.
John

Hi,
Think you should run through the SN checklist, it’s very useful. Remember to record all your measurements

Wanted to caution you regarding troubleshooting your 02’s. Never take a typical resistance measurement across the leads unless you want to replace it, the VOM’s reference voltage to test resistance will melt it.

Hi,
How’d the troubleshooting coming along, & were you able to locate the issue? If you have- great! If not, happy to help you out however necessary if you’re still looking.
Best!
-John

Black GT said:

Actually now that I see it in the daylight it comes off the back of the throttle body.. I replaced the front section and just noticed the other half that disappears on the right side of the firewall is split also. I am just going to plug the section I replaced for now. Anyone know where the other end leads to? Thanks

Click to expand...

I had a similar problem, look toward rear of the engine bay passenger side for a canister, off that canister there should be a hose that goes to a adapter, this hooks into the hose coming off the back of the TB. Assuming of course we are talking about the same hose but I'm pretty sure we are. I'll post up a pic when I get back home. Also I think this is what gives vacuum for our dampers in our a/c controls but I could be wrong.

Hi,
Well, whatever the hel^ it is, it clearly doesn’t like being filleted it’s great to hear replacing it cleared up your issue!!