vacuum leak

[91fox]

Hey everyone, so i'm still getting p0171 and p02197 (lean codes) I just replaced the intake manifold gaskets and the tuning valve o'ring (smoke checked and confirmed they were leaking). Everything is reinstalled, and the codes just now came back.. I can hear and audible hiss and smoked the system once more, no smoke visible. (I introduced the smoke from the vac line going to the hydroboost). Wouldn't you know it... the hissing sound seems like it's coming from that area, with the engine running, leading me to believe it's either the purge solenoid or the booster. When I step on the brakes and hold the pedal the engine wants to stall. My question is, is this normal? Can a faulty booster through engine lean codes? Thanks in advance,

 

[Hamfisted]

Yes it can throw a lean code and might be big enough to stall the motor with a leaky brake booster. That's a pretty big vacuum line.


https://www.rockauto.com/en/catalog...56,brake+&+wheel+hub,power+brake+booster,1884

 

[91fox]

Update: So I went back out there and determined the hissing sound is coming from the hose going to the solenoid from the intake manifold (4.6l) so i replaced the hose, and the new hose is still making the same hissing sound. The sound is drastically muffled when i put my hand over it (very close to the solenoid end) i'm not sure what to make of it... it sounds like its really pulling some air from the solenoid or vise versa.

 

[Hamfisted]

Are you talking about the Evap Solenoid ? It should not be hissing either.

https://www.rockauto.com/en/catalog...on,vapor+canister+purge+valve+/+solenoid,4936

 

[91fox]

Yes, the line going from the intake to the vacuum canister purge valve/solenoid, that hose is making a loud hiss, even though I just replaced it with a brand new hose from AutoZone. So, I'm not sure what exactly is going on

 

[91fox]

Does anyone else hear a hiss coming from the purge solenoid with the engine running? I'd like to confirm if that is just a side effect of the part functioning or if it indeed is malfunctioning. Thanks again in advance everyone!

 

[Hamfisted]

Generally speaking, any "hissing" is a vacuum leak. I can't say that I've ever heard hissing from any of my vehicles purge valves. That vacuum line that comes off the intake manifold is also notorious for deteriorating and rubbing off on your hands. They're still available from Ford and Dorman.

 

[91fox]

Update: after clearing the codes, codes p2197 and p0174 came back (both indicating bank 2 lean), I took some pictures of the fuel trim values I'm seeing, I don't know what to make of them, however, they seem to hover in the negative range and very rarely go positive. At this point I'm not sure what the issue may be.. but as always thanks for any positive input I may receive from more experienced individuals!

 

[Hamfisted]

How old are your front oxygen sensors ? Most likely the front bank 2 sensor is bad. If you already smoke checked it and sealed all the vacuum leaks. Compare the output voltages on the forward oxygen sensors. You'll probably see the bank 2 sensor stagnant, as the bank 1 sensor fluctuates up and down as you rev the motor.

 

[91fox]

They both seem to be switching, both sensors are practically new as I replaced the sensors last year and have used the truck extremely little (they were Bosch 15717 I believe) I only replaced the upstreams on both banks. I'll go back out and confirm they're switching.

 

[91fox]

After a quick stomp on the gas peddle the engine definitely is "searching" as it's settling back down to idle speed

 

[91fox]

Just decided to look at trims again, and this is what I saw. Is this due to the pcm commanding the maximum amount of fuel because of the lean codes?

 

[MrBlargMan]

Just decided to look at trims again, and this is what I saw. Is this due to the pcm commanding the maximum amount of fuel because of the lean codes?

View attachment 37289

Yes. The PCM is dumping as much fuel as it can to compensate, and it is still not enough. Thus your lean codes.
Based on those fuel trims, you either have way low fuel pressure, or there is definitely a vacuum leak.
If your EVAP purge valve is hissing, replace it. It should not be doing that.

 

[91fox]

I thought fuel was an issue with this thing as well... A couple of months back I replaced the fuel pump with a delphi brand pump... I've changed a lot of parts on this thing and have yet been able to figure out what the actual cause is.. I guess I'm going to have to go buy a pressure tester and see what type of pressure I've got, I just looked at the pcv elbows on the drivers side bank, one of them is dry rotted, so ill replace it but I severely doubt that's the cause... I don't hear any exhaust leaks, I smoked the system and cant find a vac leak.. so I'm utterly at a loss as to what's causing this issue other than possibly the purge solenoid ( but I don't know how to confirm that it is indeed failed)

 

[91fox]

Could someone educate me as to what all of the vacuum lines behind the drivers side front tire do and if those could have any correlation to the codes that I'm currently experiencing?

 

[MrBlargMan]

Just a heads up, those Delphi pumps are shit. I replaced 3 of them in my Expedition over 2 years. I finally got sick of it and put in a nice AEM 340lph pump. No issues since.

If you are spraying break cleaner or carb cleaner around all of the hoses and intake and are not detecting any kind of vacuum leak, I would be checking your fuel pressure next.

 

[91fox]

^ exactly what i just did, still need to test fuel pressure

 

[Hamfisted]

Is your purge valve solenoid still hissing? Or did you replace it?

 

[91fox]

Im getting it in the morning, it had to be ordered, I'm also going to buy a fuel pressure test kit tomorrow to check out the pressures. Finally I'm going to take of the throttle body and inspect it... Not really sure where else to turn, I dropped the spare tire today to make sure the canister hoses were connected and not leaking and everything appeared to be fine. The issue is still present however, when I quickly snap the throttle the engine seems to stay revved up for longer then normal and then it gets real choppy when trying to idle out, however it only seems to do that one out of every four attempts. Needless to say, it's awful strange.

 

[Hamfisted]

Ok, well put the new purge valve solenoid on and give it a chance before you tear the throttle body off. How's the throttle body look inside? Fairly clean, no carbon/soot build ups ?