Interpreting Freeze Frame Data for Troubleshooting Lean Codes - Ford Truck Enthusiasts Forums



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Interpreting Freeze Frame Data for Troubleshooting Lean Codes

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Old 01-13-2018, 05:38 PM
gushauler gushauler is offline
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Interpreting Freeze Frame Data for Troubleshooting Lean Codes

HELP! I've been chasing the dreaded P1071 - P1074 lean conditions for months on my '04 Expedition 5.4. I've replaced the entire PCV tubing + Valve system with the factory replacement, used a smoke test, replaced purge lines, and pulled out a lot of my hair. The only thing that I think I haven't replaced is the Intake gaskets. I can't see any smoke coming from them, but that's about the only thing left that I can think of. Could I please ask a BIG favor? Could someone use their crystal ball and interpret the freeze frame data I recorded the last time the p0171 code threw and let me know what they think? Is it possible there's a bad O2 or MAF sensor? Replacing the intake gaskets looks like a long job in 17 degree weather and I really don't want to do it if the code is just going to come right back. Here's what I've got:

Fuel System - Closed
Calc Load - 20%
ECT - 176
STFT B1 - 11.7%
LTFT B1 - 25.8%
STFT B2 - 10.9%
LTFT B2 - 18.8%
Engine RPM - 614
Speed - 0
Spark Adv - 12
IAT - 39.2F
MAF - 0.7 lb/min
TPS - 18.8%
O2S B1 S1 - 0.310v
STF1 S1 - 11.7%
O2S B1 S2 - 0.195v
STFT B1 S2 - 99.2%
O2S B2 S1 - 0.070v
STFT B2 S1 - 10.9%
O2S B2 S2 - 0.320v
STFT B2 S2 - 99.2%

Does this all still scream "vacuum leak"?
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Old 01-13-2018, 07:25 PM
projectSHO89 projectSHO89 is offline
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Have you verified adequate fuel pressure? "Lean" codes, although most frequently caused by un-metered air in the intake that hasn't been measured by the MAF, can also be caused by a weak fuel supply.

The only thing that looks out of the ordinary (beside the trims) is the ECT at 176. Does it get fully up to temperature of 190-210 during normal operation?
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Old 01-13-2018, 09:08 PM
pdqford pdqford is online now
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Quote:
Originally Posted by gushauler View Post
HELP! I've been chasing the dreaded P1071 - P1074
>
>
Could I please ask a BIG favor? Could someone use their crystal ball and interpret the freeze frame data I recorded the last time the 1071 code threw and let me know what they think? Is it possible there's a bad O2 or MAF sensor? "?
Im gonna guess that you really mean P0171 - P0174.

I agree that unmetered air is typically the cause of these lean codes, and the fact that the freeze frame data snapped when the code last tripped shows that the engine was at 614 RPM, and the calculated load on the engine was 20%. This indicates that the engine was more than likely at high vacuum when a vacuum leak would have a significant effect, and the engine was under very light load which would require minimal fuel flow. So I still think unmetered air is the bigger possibility.

When you smoked it did you use a high intensity light to look for the smoke? And did you look very closely at the point where the oil dipstick tube enters the engine block?

And did you carefully check the PCV fresh air side for leaks?

Since you are getting codes for both banks, probably both head gaskets didnt let go at once so I would put them down lower on the list of possibilities. You could disconnect and cap the EVAP purge line and see if it still throws the lean code. If it does, the EVAP system is not the cause. Has the MAF ever been cleaned?
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Old 01-13-2018, 09:59 PM
gushauler gushauler is offline
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Thank you for the quick replies. Here are some answers:
1. Yes, I meant P0171-P0174. Sorry.

2. No, I haven't checked fuel pressure. I think I could with a loaner tool from an auto parts store right? What's the correct pressure range?

3. I have a home-made smoker that uses low PSI. When I did smoke it, it was at night, I used a super bright flashlight. I connected the smoker to the brake boost line. Most of the smoke was coming out through the air filter joint where the two halves of the Filter housing separate. I could not see any smoke coming from anywhere else. I did not check the oil dipstick entry point.

4. I will try capping the evap purge line. Last night I took it off, and put my finger in one end while blowing through the other, couldn't feel any leak.

5. I'm not really sure what you mean by the fresh air side of the PCV. The whole line from the PCV, to the back of the throttle body adapter was replaced with a new part from Ford this past week. ($85! Ouch!)

6. Is there any possibility of the EGR valve playing into this? Probably not right, it would throw a code if it weren't working right, or the DPF sensor? I did just replace one of the two rubber lines going from the EGR tube to the DPF sensor because it was starting to crack.

Has anyone tried the trick of testing Intake Gaskets where spray around the intake base with a bottle of water with the engine running to see if it stumbles? Any harm in trying this?
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Old 01-14-2018, 07:31 AM
projectSHO89 projectSHO89 is offline
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Has anyone tried the trick of testing Intake Gaskets where spray around the intake base with a bottle of water with the engine running to see if it stumbles?
Usually doesn't work, the computer is way too fast. What you can do is set up your scan tool to monitor the STFTs in real time and watch those while spraying with a combustible (I use brake cleaner). When it gets sucked in, the trim(s) will spike.
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Old 01-14-2018, 08:09 PM
pdqford pdqford is online now
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Originally Posted by gushauler View Post
5. I'm not really sure what you mean by the fresh air side of the PCV. The whole line from the PCV, to the back of the throttle body adapter was replaced with a new part from Ford this past week. ($85! Ouch?
That hose carries crankcase fumes from the PCV valve back to the intake manifold to be burned.

Typically there will be another hose that brings fresh FILTERED air (downstream from the air filter and the MAF) and directs it to the valve cover opposite of the side where the PCV valve lives. This is what I call the fresh air side of the PCV system. It supplies fresh filtered air (metered by the MAF) to replace the crankcase air pulled out via the PCV valve.

If this fresh air hose has a leak (or is missing), unmetered air will get sucked in this hose, go through the crankcase, through the PCV valve and into the intake manifold and cause lean codes. (Ditto if your dipstick tube has a rusted out hole in it or a poor fitting dip stick seal.

When you do your smoke test, pull the air filter off, or disconnect the inlet tube from the air box and fit a plastic clove over the end to seal it so smoke doesn’t spill out of it. That will allow a couple of pounds of smoke pressure to make leaks more evident.
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Old 01-14-2018, 10:58 PM
gushauler gushauler is offline
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Cool, thanks Jim. I'll try the glove trick. I was getting a lot of smoke coming out of the air box, and maybe that "clouded' (hahaha) my sight line of other smoke escaping.
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Old 01-15-2018, 12:49 PM
gushauler gushauler is offline
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It snowed here overnight, so I wasn't able to get down to the parts store to get a pressure gauge for the fuel rail. But I did make progress. I tried spraying all the usual vacuum lines with carb and brake cleaner, with no change to engine RPM. Then gave the water bottle a try and hosed down all the connections. Still fine. Moved on to intake manifold gasket, and bam! The front driver's side started sucking in the water with a distinct hiss and ran rough. When I moved to the back I didn't hear a hiss, but it also ran rough. I did try torquing the intake bolt just a tiny smidge, and re-sprayed. Now it doesn't seem to hiss, but I am still going to replace the intake gaskets. I'll still check the fuel pressure when I get a chance, but since the code only seems to throw at idle, not higher RPM, I'm thinking I'm on the right track with the intake gasket. If this doesn't fix it, I'll check be in in case anyone finds this thread in the future.
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