Interpreting Freeze Frame Data for Troubleshooting Lean Codes

[murdoc]

HELP! I've been chasing the dreaded P0171 - P0174 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 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 - 39.2°F
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"? Or should I look somewhere else?

 

[1955moose]

If you've done a smoke test and saw nothing, don't chase your tail on the intake. As we've stated a million times, do a fuel pressure test, you need to get a baseline. If all checks out there, I'd check voltage at the questionable cylinders fuel injector plugs. If that checks out swap in new injectors for those cylinders. According to codes that's #1 and #2 cylinders, at least their relatively easy to get at.

Sent from my N9131 using Tapatalk

 

[murdoc]

Thanks. What's the spec for the fuel pressure?

 

[murdoc]

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.

 

[murdoc]

Just wanted to follow up on this thread in case anyone in the future stumbles accross it. (I hate when I find an old thread that just dried up with no resolution.)

So my quick-fix of tightening the intake some more did not work. I ended up replacing the Intake Gaskets. When I ordered the parts I got the upper Intake seal, lower gaskets, crossover pipe gaskets, thermostat and thermostat O-Ring. I certainly could have done the job without taking the coolant crossover pipe off, but I figured, since I'm there...

The job took a long time, and I ran into three problems:
1. This engine has 249,*** miles on it, so all the plastic is old and brittle. One of the retaining clips on the rear coil on the passenger side broke. I had to do a hack job with some zip-ties to fix it. I will likely have to find a replacement harness at some point to fix that for real.
2. The coolant crossover pipe is held on with six or so bolts. One of them was stuck, and snapped off. Luckily it snapped off above the threading, so I could get some vise-grips on it and turn it off with some lubricant. And Luckily I had a metric bolt on hand to use in its place.
3. While taking off the vacuum line "tree" or harness that goes from the vacuum reservoir around the top of the engine to the fuel regulator, purge valve, EGR valve, ect... The manual says to disconnect the line at a coupler located right in front of the PCM on the passenger firewall. This coupler was buried under enough cables and lines that it took me several attempts to locate it and isolate the correct line by tracing back from the engine. When I did my guts sank because the stupid coupler was rotted and had a huge crack in it. I replaced it with some new hose I had on hand.

In retrospect I'm thinking this is likely what was causing my codes. But the intake was sucking in air as well, I had the parts, so I went ahead and replace the intake gaskets anyway for peace of mind.

I got a new OBDII bluetooth interface today, hooked it up, and my fuel trims are back to normal at idle now. So that fixed that problem. Now I just need to pretend I don't hear that clicking coming from the engine....