2002 SCREW 5.4L, 177K
Need some help fellas. I truly believe I have read all of the 171 / 174 threads and have exhausted the info offered therein. In an effort to avoid wasting anyone's time, I have gathered all of the info that I can imagine could be useful. Please hear me out, I have a ton of info here but I’ll start with the issue:


A P0171/0174 triggered by a second start following a 5-minute warmup (ETC = 180F) with 50-60F ambient air. Also occurs on it’s own after the PCM gets tired of the LTFTs getting pushed (obviously). No rough idle/rough running, highway mpg is 17-18--good. Hi vacuum/low throttle mpg is not great, and I do take that as a vacuum issue. I’m trying to rule out a MAF (see MAF troubleshooting results below).

I also have two broken studs on the #4 exhaust and I know I need to fix that eventually. Leak is only noticeable during first 30 seconds following startup…again, I know I need to fix that. If that's what we think the issue is, great! But if not.... All of the Bank 2 studs are good though, so it’s hard to believe an exhaust leak is causing both 171 and 174...


Yes, I have freeze frame and live data:
All the tables were relatively young, approx. 30 mi of driving cycles to make all monitors RDY was all that was stored since the last wipe. I'm imagining we're going to want a longer observation period for those LTFTs...but here's what I have at this time:


Freeze Frame:
ETC 180F
STFT1 25%
LTFT1 24.2%
STFT2 20%
LTFT2 19.5%


Live Data (Immediately after DTC):
ETC 190F
Load 25%
STFT1 0.8%
LTFT1 29.2%
STFT2 0.8%
LTFT2 28.1%
IAT 64F
02B1S1 0.1-0.2 VDC
STFTB1S1 1-3%
O2B1S2 0.66V
O2B2S1 0.1-0.7 VDC
STFTB2S1 -1 – 1%
O2B2S2 0.5 VDC


Other key points:


*Plugs were replaced 2000mi ago with Motorcraft SP479, no anti-seize, torqued to 25 ft-lbs. Visual inspection 2000mi later shows nothing noteworthy. Plugs are burning clean (I have a picture if you’d like).


*New air and fuel filters, stock.


*Fuel rail pressure is 36psi and is at 32psi after being shut off for 5 minutes.


*Intake manifold gasket has NOT been replaced.


*DPFE sensor is original, lines are new.


*PCV elbows at throttle body and valve are serviceable. I am waiting on a Motorcraft PCV valve (current valve is a new Dorman). I know TSB 04-17-4 specifically says it needs a Motorcraft part.


*O2S graphs show smooth cycling. Nothing erratic.


*LTFT1 is 29.2% at idle and is 16.4% at 2500 RPM (less than the 15% drop mentioned in TSB 04-17-4). LTFT2 shows a similar ~12% drop. Do we still think it’s a vacuum leak?


*DIY smoke-test revealed a leaking EGR valve gasket. Replaced gasket, no leak, not the fix.


*MAF was shot while connected, with multimeter: good power, good ground, good 2nd ground, sensor transitioned voltage smoothly, 0.75 VDC baseline (idle), 1.22 VDC @ 1500 RPM, 1.6 VDC @ 2500 RPM. (The info I had, prescribed a 0.9-1.0 VDC baseline with 1.5V at 1500 RPM and 1.75V at 2500 RPM. A clue?). During the check, ambient temp was 68F, ECT was 190F.


*MAF under same conditions at idle is reading ~0.52 lbs/min (my info prescribed 0.657 lbs/min)


*I am seeing a ~10% drop in STFT from 2500 RPM vs. idle when in a colder ambient temp (50-55F). This is with all monitors RDY /after drive cycles. Does this fluctuation in STFT and LTFT point to a MAF sensor?


Again, I have made every effort to address the obvious and bring to the forum my "brick wall" problem. Relying on you guys, thanks very much for running such a great forum!

 

Got an update in hopes of getting a little help:


Did a leak and ops check on the EGR Valve, DPFE sensor, and EGR solenoid: Valve opens clean with 10"Hg and closes fully, no carbon buildup. Did a vacuum check with a gauge on it while driving and it builds to 7" of vacuum under light acceleration, then snaps to 0 when accelerator is lifted. All good there.


Shot for voltage on the DPFE sensor. 1.0 VDC reference with no vacuum applied to the EGR valve. Then shoots up to ~3.5 V when vacuum is applied, right before the engine dies...normal.


Sealed off the air cleaner tube and both vacuum connections, pressurized it by breath and found zero leaks.


I can't hear the slightest hiss from anywhere on the blasted motor. I can't get a STFT spike with propane or spray to save my life.


Without any ideas coming in, I'm at a crossroads: throw a MAF at it (it's gonna be a garb-o Dorman one from the LAPS) or dive into an intake manifold gasket that I can't even prove is bad?


If anyone could jump in, I'd be hugely re-charged...

 

Just want to close out the thread for any future readers. Starting this thread didn't turn out to be the most productive thing to do, but alas, off we go:

A new Dorman intake manifold (part number 615-188) ended up being the fix for my high fuel consumption at idle. You can find a lot of the following information in the many other threads out there, but I'll collect it here and summarize my situation:

The MIL would come on accompanied by a P0171/174 code for two lean banks. This would only happen after a cold start (55F) and about 5 minutes of low-speed driving (<30mph). I could induce the light by shutting down and immediately starting back up after that quick 5 minutes of driving.

I had NO ROUGH IDLE or hesitation to speak of. Here is what I advise based on this experience.

1- Get a scanner with real-time and freeze-frame capability. I found this one for $47 and it was THE REASON I was able to get this truck fixed.
The scanner is required because you need to be able to read Short Term Fuel Table data when you are searching for vacuum leaks with the spray method. Computers are too fast to allow the engine to race when you introduce a richer mixture.
Also, reading the Long Term Fuel Table data was necessary in determining the total fuel addition (by adding STFT to LTFT). I was finding LTFT at 29.7% during troubleshooting. YOU NEED THIS SCANNER.

2- Start simple and don't shotgun parts at your truck. When you get frustrated, everything starts seeming like a good idea to replace. I should not have changed my MAF sensor. It was reading 0.49 lb, when the prescribed reading was .657. The voltage was .25V low. But the MAF was doing its job. It wasn't reading full airflow because the remaining 0.16 lb of air was leaking in AFTER THE MAF SENSOR. In most cases, you can prove something is faulty before replacing it.
Look for O2 sensors to be cycling on your reader. If they are, search elsewhere. If your MAF is reading low, keep it in mind and keep searching for leaks.

3- Vacuum leaks are the most common cause for a combined P0171/P0174. The most thorough way to approach it is to start at the air filter and methodically work your way back. Here's are some things to look at, remember them when you are spray-checking as well:
-MAF wire harness boot for tight installation (this is located just to your left of the air filter quick release clamp, on the bottom side of the duct)
-Air duct hose clamps (these are the clamps secured with 8mm drive hose clamps--there is one at the filter end and one at the throttle body)
-Two large vacuum hoses on driver's side of air duct, forward of the throttle body (check for a tight fit)
-All hose connections on the throttle body need to be tight. If they slide right off, replace them
-DPFE sensor hoses, 2 (the DPFE sensor is mounted on a bracket just to your right of the throttle body, just forward of the EGR valve)
-DPFE solenoid vacuum lines, 2 (located on the same bracket, just to the right of the throttle body)
-PCV VACUUM HARNESS. There is so much information out there about the elbows for the PCV harness, and if you're reading this, you've probably already checked that harness out...ESPECIALLY the big elbow attached to the very center of the back of the intake manifold, way back at the firewall. BE SURE you have checked these elbows with the ENGINE RUNNING. They can collapse under vacuum. Also, get a Motorcraft PCV valve and grommet.

If all these items pass your inspection, the next step is to start spray testing:
1) Hook up your scanner and monitor the STFT1 and STFT2. Use CRC Electronic Contact Cleaner; it is easier on rubber components, intended for electrical components, and still highly combustible.

2) Using short bursts, 3-4 at a time, shoot the above mentioned areas with the straw attached to focus the spray. You are watching for your STFT values to decrease in value (a sharp 4% or more). It will be a noticeable change when you find a leak.

3) Spray both ends of all the hoses mentioned above.

4) If you haven't made any finds on the air duct, and vacuum hoses attaching to the throttle body:
-Don't forget the bottom edge of the mating surface of the throttle body
-Move down to the intake manifold. Spray down around the bottoms of the fuel injectors (watch those STFTs!).
-Still nothing? Now spray UNDER the intake manifold. There is a big, open cavity located just behind the alternator. Spray back under there. This was where I finally saw the STFTs come crashing down.

If you have found your leak here, I figure you have two options:
1- Assume the intake manifold gasket is bad and go for replacing it
2- Decide that either the gasket is bad or the manifold is cracked OR BOTH. In my opinion, I'd rather replace both with the same amount of work than find that the gasket didn't fix it and have to do the whole job again.
-The top-quality OE gasket from Felpro is $60 on Rockauto.com, and $84 at Autozone.
-The aftermarket intake manifold from Dorman is $170 from Amazon and comes with better gaskets

Additionally, the factory intake manifolds are notorious for leaking coolant at the crossover ports to the passenger cylinder head. I say just replace the manifold.

That job, while not easy, is very manageable and doable when you take your time, label everything as you disassemble, and obey the torque patterns and specifications.



To be clear, this shouldn't be a part to just guess on. This is the end of the vacuum chain. It is the last stop before the intake valve in the head. Before you go for the intake manifold, you have to KNOW that you don't have a leak before the manifold.

There are some great write-ups on how to accomplish that job, which I will not cover here. But do your homework and preparation before you jump in and you'll be in great shape.

Hopefully someone out there finds this useful down the road. There is just no reason to surrender to the infamous 171/174 nightmare. You can fix it! Good luck!

 

Thank you for posting such a complete fix and diagnostic approach. I don't own a 5.4 but I am sure that others will find this very useful. My first thought when I read your post was a manifold because of the motor temp. making the MIL light up, but thought others with more experience would jump in and help.

Anyway good job and congratulations.

 

Thanks! This was a tough one, for sure, considering I had no knowledge or experience on the engine when I started out with this issue. And even though I couldn't get a reply on THIS thread, all of the info out there was still enough to keep me headed in the right direction and out of the dealership's garage. These forums are such a valuable resource!

 

@jgger is spot on - and I do own a 5.4. Thanks to @02RedScroo for well documented and well written repair guide founded on logical, straight forward diagnostic procedures. These modern, heavily computer based engines require a more methodical approach to diagnosing problems than the cars of my 1960's high school days. And this thread shows a good example of that.


Thanks


F150Torqued

 

I do greatly appreciate the high-five. A jet mechanic at my day job, I tell ya, this was WAY more confounding than most problems at work. Still fun though. These trucks are just like women: the nicer you are to 'em, the meaner they are to YOU!

 

It's kind of ironic that you didn't even bother going back to the website where you were told HOW to diagnose the problem and provide any updates there nor even acknowledge WHO gave you the insight on what to look for.... yet you provide a full summary HERE where zero assistance was provided.

 

I'm not sure what you mean. It's all right there on my similar thread on ford150.net, here's the link http://www.fordf150.net/forums/viewt...?f=71&t=119840. I kept them both going.


Also, I've got you mentioned under step 1 of my most recent write-up on the above-mentioned thread. I know you've been helping people on these forums for years, and I sincerely thank you for helping me get back on the road as well.

 

I was at my wit's end and ready to give up until I read this. You have provided so much insight as to what had been going on with my Ford. It is Dad that nobody chimed in to assist you and I respect your efforts to help others even when nobody helped you. Thank you so much.

 

[QUOTE=02RedScroo;5167032]Just want to close out the thread for any future readers. Starting this thread didn't turn out to be the most productive thing to do, but alas, off we go:

A new Dorman intake manifold (part number 615-188) ended up being the fix for my high fuel consumption at idle. You can find a lot of the following information in the many other threads out there, but I'll collect it here and summarize my situation:

The MIL would come on accompanied by a P0171/174 code for two lean banks. This would only happen after a cold start (55F) and about 5 minutes of low-speed driving (<30mph). I could induce the light by shutting down and immediately starting back up after that quick 5 minutes of driving.

I had NO ROUGH IDLE or hesitation to speak of. Here is what I advise based on this experience.

1- Get a scanner with real-time and freeze-frame capability. I found this one for $47 and it was THE REASON I was able to get this truck fixed.
The scanner is required because you need to be able to read Short Term Fuel Table data when you are searching for vacuum leaks with the spray method. Computers are too fast to allow the engine to race when you introduce a richer mixture.
Also, reading the Long Term Fuel Table data was necessary in determining the total fuel addition (by adding STFT to LTFT). I was finding LTFT at 29.7% during troubleshooting. YOU NEED THIS SCANNER.

2- Start simple and don't shotgun parts at your truck. When you get frustrated, everything starts seeming like a good idea to replace. I should not have changed my MAF sensor. It was reading 0.49 lb, when the prescribed reading was .657. The voltage was .25V low. But the MAF was doing its job. It wasn't reading full airflow because the remaining 0.16 lb of air was leaking in AFTER THE MAF SENSOR. In most cases, you can prove something is faulty before replacing it.
Look for O2 sensors to be cycling on your reader. If they are, search elsewhere. If your MAF is reading low, keep it in mind and keep searching for leaks.

3- Vacuum leaks are the most common cause for a combined P0171/P0174. The most thorough way to approach it is to start at the air filter and methodically work your way back. Here's are some things to look at, remember them when you are spray-checking as well:
-MAF wire harness boot for tight installation (this is located just to your left of the air filter quick release clamp, on the bottom side of the duct)
-Air duct hose clamps (these are the clamps secured with 8mm drive hose clamps--there is one at the filter end and one at the throttle body)
-Two large vacuum hoses on driver's side of air duct, forward of the throttle body (check for a tight fit)
-All hose connections on the throttle body need to be tight. If they slide right off, replace them
-DPFE sensor hoses, 2 (the DPFE sensor is mounted on a bracket just to your right of the throttle body, just forward of the EGR valve)
-DPFE solenoid vacuum lines, 2 (located on the same bracket, just to the right of the throttle body)
-PCV VACUUM HARNESS. There is so much information out there about the elbows for the PCV harness, and if you're reading this, you've probably already checked that harness out...ESPECIALLY the big elbow attached to the very center of the back of the intake manifold, way back at the firewall. BE SURE you have checked these elbows with the ENGINE RUNNING. They can collapse under vacuum. Also, get a Motorcraft PCV valve and grommet.

If all these items pass your inspection, the next step is to start spray testing:
1) Hook up your scanner and monitor the STFT1 and STFT2. Use CRC Electronic Contact Cleaner; it is easier on rubber components, intended for electrical components, and still highly combustible.

2) Using short bursts, 3-4 at a time, shoot the above mentioned areas with the straw attached to focus the spray. You are watching for your STFT values to decrease in value (a sharp 4% or more). It will be a noticeable change when you find a leak.

3) Spray both ends of all the hoses mentioned above.

4) If you haven't made any finds on the air duct, and vacuum hoses attaching to the throttle body:
-Don't forget the bottom edge of the mating surface of the throttle body
-Move down to the intake manifold. Spray down around the bottoms of the fuel injectors (watch those STFTs!).
-Still nothing? Now spray UNDER the intake manifold. There is a big, open cavity located just behind the alternator. Spray back under there. This was where I finally saw the STFTs come crashing down.

If you have found your leak here, I figure you have two options:
1- Assume the intake manifold gasket is bad and go for replacing it
2- Decide that either the gasket is bad or the manifold is cracked OR BOTH. In my opinion, I'd rather replace both with the same amount of work than find that the gasket didn't fix it and have to do the whole job again.
-The top-quality OE gasket from Felpro is $60 on Rockauto.com, and $84 at Autozone.
-The aftermarket intake manifold from Dorman is $170 from Amazon and comes with better gaskets

Additionally, the factory intake manifolds are notorious for leaking coolant at the crossover ports to the passenger cylinder head. I say just replace the manifold.

That job, while not easy, is very manageable and doable when you take your time, label everything as you disassemble, and obey the torque patterns and specifications.



To be clear, this shouldn't be a part to just guess on. This is the end of the vacuum chain. It is the last stop before the intake valve in the head. Before you go for the intake manifold, you have to KNOW that you don't have a leak before
I've replaced coils, plugs, injectors. Didnt throw 171 n 4 until after I replaced these parts. I dont think I have a leak. I sprayed the motor and smoked it.
pcv valve is just a heated tube. Help

 

What's your Vct doing!??? Prolly not tripping your check light or scanner...kinda like ford oil gage ... worthless..

 

2002 didn't have VCT.