P0174 v8

[Kidd7]

I have a 2000 v8 EX AWD. It started throwing a P0174 Code (pending) & P1151 (Current) 2 days ago. I did some digging, cleared the codes and data logged. The P0174 came back and it occasionally bogs and loses power. Many of the things I've read state clean the MAF, look for vacuum leaks; those things should affect both banks though.

Fuel trims and O2 sensor 1 look good on bank 1.
Fuel trims and O2 sensor 1 on bank 2 are a different story. At times they look normal, then O2 goes low and fuel trim maxes out. it's intermittent. I'm including a pic below of the data, in this case it seems to get worse as we drive.

My plan is to swap bank 1 O2 and bank 2 O2 to see if the trouble follows the O2 sensor, then troubleshoot accordingly. I did look at the connector and wiring, it appears OK and connection was solid. There is some fluid on the CAT as it crosses under the engine/ tranny near that O2 sensor, could have contaminated the O2 sensor / wiring?

Any other suggestions to troubleshoot??

 

[J_C]

If it runs rich due to a bad O2 reading, right up to the max it will enrich, it should just be less fuel efficient and not enough performance difference to call bogged down unless you're overstating it. I could be wrong but AFAIK a contaminated O2 sensor will read less than actual O2 and one shorting out or open circuit, the signal will trigger a different invalid sensor signal code.

I suspect you have an intake manifold gasket leak on bank 2, and that P0174 code is the O2 sensor reading correctly. You could try spraying starter fluid (or whatever you have that's safe yet combustible) around that bank's intake manifold gasket area, to see if it improves or do a smoke test but that's harder to find when intermittent.

Frankly if your O2 sensors are the originals, considering their age, if you were going to try swapping them, instead I'd just put new ones in, at least for the upstream sensors which matter more. They may be a bit stuck in the pipe after all this time so if they don't come loose easily, I wouldn't push it just "yet".

 

[Turdle]

Imo there is a fouling fuel injector on driver side.

 

[Kidd7]

I've not driven it under these conditions, the bogging & power loss symptoms are descriptions from my wife.

I'll check for the intake gasket leaks & replacing the fuel injectors have been on my to do list, apparently that just got moved up the list.

 

[J_C]

Be sure to only do one thing at a time and test... it becomes a PITA to do too much at once then wonder if something else went wrong.

 

[410Fortune]

intake leak would effect both banks 99.9% of the time
with no p0171 we can almost rule out intake air leak

bank 1 injector failing like @Turdle said
Check fuel pressure first

p1151 lack of switching, sensor bank 2 indicates lean.....interesting it did not come back
lack of switching is almost always a lazy 02 sensor

i would replace both upstream sensors with new bosch
bank 2 sensor 1 is a ***** to get to but can be done

fuel rail pressure should be 64 psi +/-

 

[Kidd7]

Update: getting to the intake gasket area with spray is a PIA. I did spray some starter fluid around the intake with no noticeable changes, although it seemed most of it was blown away by the fan. If I do that again maybe disco the belt.

I was looking at TSB 04-17-4 Specifically step 2:
i. If the fuel correction decreases, more than 15%, (example: was +31% at idle on bank 1 but changed to +12% at 2500RPM on bank 1, a decrease of 19%) then a vacuum leak is most likely causing the lean diagnostic test codes. Proceed to Step 3.
j. If the total correction remains approximately the same then the lean condition is not caused by a vacuum leak. Refer to the for further diagnostics.

Fuel trims on bank 2 at idle are -5; at ~2500 RPM they jump to +15. So opposite of whats stated above.

I'll get a fuel pressure tester from O'Reillys today and see what I have there.

I looks like I need to remove the intake to access the injectors anyway. So I'll get them on order as well as O2s.. I did notice some RTV where the lower intake mates to the head on the drivers side.

Thanks for the help so far, I'll keep ya'll updated.

 

[410Fortune]

rtv on the lower intake to the head is factory

fuel pressure test will tell the tale

yes upper intake comes off to get to fuel rail
You will need to disconnect the EGR hose on passenger exhaust manifold good idea to spray some pb blaster in the fittings now

 

[Turdle]

I use an unlit propane hand torch , it allows you to direct raw propane to suspect areas. Removal of belt will help.

Don't forget new blue o rings for the injectors. A failing lower o ring could leak unmetered air.

 

[Turdle]

rtv on the lower intake to the head is factory

fuel pressure test will tell the tale

yes upper intake comes off to get to fuel rail
You will need to disconnect the EGR hose on passenger exhaust manifold good idea to spray some pb blaster in the fittings now

You might squeeze by just removing egr valve from elbow,

 

[Kidd7]

Fuel pressure is steady at 64 psi. and dropped pretty quickly to 59 psi when shut down, then seems to be slowly decreasing. I'll check again in a few minutes.

Side note: I've been chasing an exhaust leak that the exhaust manifold gasket didn't fully fix. I had to climb above the engine to get the pressure gauge to seal and a good reading. That leak is louder from above, still on the passenger side (bank1) which is odd since I'm getting a code and odd fuel trims on bank 2. Just figured it was worth noting.

Also, I had forgotten about the propane trick. I'll plan to try that later with the belt off.

After about 20m or so fuel pressure dropped to 38 psi. That points to a leaking injector, correct?

 

[Kidd7]

Did the propane test around the intake and no change to the RPMs.

 

[Kidd7]

Holy crap you ain't kidding that O2B1 is obnoxious. I was going to try swapping B1 & B2; even if I could get O2B1 out the wire lengths are different and won't reach, so scrap that idea. I did pull Bank2 O2 sensor and a picture is attached. It looks like crap, put it all back together and now the O2 is not switching at all. I'm ordering 2 new O2 sensors.

How in the world do you get Bank1 O2 outta there? I think I can work my arm up in there to access the plug, but it's tight.

 

[410Fortune]

Cut the sensor off and use a socket? Or cut the pigtail off and use box end wrench

 

[Turdle]

There is an access panel under the console. For me, removing console makes it smoother.

 

[Kidd7]

Update: O'Reilly had an O2 sensor in stock, so I swapped out bank2 O2 this morning. I took it for a test drive and both O2 are switching correctly and fuel trims are back within spec. My wife headed out to work and I have it logging, I'll look at the data when she gets home. I do plan to change out the other O2 this weekend.

Thanks for the help here.

 

[410Fortune]

fuel pressure dropping after shutoff is not a concern, it usually bleeds back into the tank

Removing the center console and seats, pulling the carpet back and getting the center cover out makes life a whole lot easier to get to the 02 sensor wires
If you cut your carpet then you never have to remove the seats again, the center console can be out in minutes and the cut in the carpet is completely covered up

 

[Kidd7]

fuel pressure dropping after shutoff is not a concern, it usually bleeds back into the tank

I have this same issue on my Cougar, there's a check valve in the tank that has worn out; it requires multiple primes to get her to start.

Removing the center console and seats, pulling the carpet back and getting the center cover out makes life a whole lot easier to get to the 02 sensor wires
If you cut your carpet then you never have to remove the seats again, the center console can be out in minutes and the cut in the carpet is completely covered up

Any pictures of this so I can wrap my head around it? Removing eats aren't a problem, I've removed a center console from a wrecked Ex before and that was a royal pain. So this seems like a ton of work to just unplug a connector.

 

[Turdle]

How to: - 2nd gen console removal

Center console removal Tools required 1/4" ratchet extensions (optional but very helpful) 8mm socket 10mm socket magnetic pickup wood block hand sledge (or big hammer) Step 1 Remove tissue box-coin holder Step 2 remove the cubbyhole compartment by pulling up and toward you Step 3...

www.explorerforum.com

 

[Kidd7]

Thanks Turdle, should have used that search feature, sorry.