P0171 & P0174 and Service Engine Soon Light

[Kenerator]

2004 5.4 EB. Service engine soon light came on. Idle is occasionally a tiny bit rough, but otherwise runs fine and there is no other indication of a problem. Used BlueDriver to check for codes. I received the following:


I cleared all the codes and the SES light went out, but light and codes returned a few days later.

I smoked the vac system using the brake booster hose as the smoke insertion point. Smoke came out of the throttle body, IAC, EGR valve and the two large hoses that connect to the air intake just prior to the throttle body. I pulled the air intake back enough to seal off the the TB and two large hoses, but still had smoke leaking at the IAC and EGR valve. No smoke anywhere else that I could see. All of the little vacuum lines appeared to be intact.
Question - Is it normal for the IAC, EGR valve to leak smoke?

Thinking that maybe there was an intake manifold leak or something like it, I put the intake back on started the engine. While running I sprayed starting fluid around the top of the intake manifold and throttle body. There was no discernable change in RPM.

So, unless my smoke test was done incorrectly, there appears to be no vacuum leaks (smoke test) or intake leaks (starting fluid test).

Were my test methodologies erroneous?
Should I start looking at component failures? i.e. O2 sensor, MAF, etc?

Any thoughts are appreciated. Thank you!
Ken

 

[Hamfisted]

It is normal for a small amount of smoke to escape from the IAC and EGR valves. It is not normal for smoke to escape from the small hoses prior to the throttle body, or any other hoses. I would connect the smoke machine's hose to the Evap vacuum supply nipple there at the top of the throttle body elbow. Just to see if the brake booster is leaking.





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[Kenerator]

Great idea Hamfisted!
I inserted the smoke at the top of the throttle body elbow as suggested. I got smoke from the usual suspects - IAC, EGR and side of the throttle body, but no smoke at the brake booster or booster hoses. However, I did find smoke coming out from under the fuel injector of the first cylinder on the passenger side. The yellow arrow in the photo is pointing where the smoke was present. The smoke looks like glare and is difficult to see in the photo. It was much more visible in person. I suspect this means bad intake manifold or intake manifold gasket.
Question - Doesn't seem plausible, but is it possible that the injector, or injector o-ring is bad and leaking?
Again, any thoughts are appreciated.
Thank you,
Ken

 

[whtbronco]

Sure it's possible you have an injector o-ring that's failed and from the looks of it I think you're on to something. I'd say it's unlikely to be the injector itself. I haven't messed with these fuel rails/injectors yet, but it's a pretty cheap and simple process to pull the fuel rail and replace the injector o-rings on the vehicles I have done so on.

 

[whtbronco]

I looked up the process in AllData. It doesn't look terrible, but AllData shows it's a more involved process than any I have done to remove the fuel rail, 2.2hrs of book time. I think I could do this on a GM 3800 in 30 minutes.

 

[Hamfisted]

To leak enough air to trigger a P0171 and P0174 at the same time it would have to be a good size leak. Not likely with a fuel injector O-ring. Much more likely to be the intake manifold gasket. Did you look around the engine with a bright flashlight during the smoke test ?



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[whtbronco]

Hmm, good point. A single injector o-ring seals a rather small gap.

 

[Kenerator]

Yes, I looked for several minutes with a bright flashlight. I scanned every hose that I could put my eyes on. There may have been a little bit of smoke at the last cylinder, same side, but I couldn't tell if it was a leak or if it was smoke carried over from the IAC. The brake booster, vac lines, vac reservoir, both sides of the engine, etc, all appeared to be intact.

I also rescanned and P0171 is now the only confirmed trouble code. P0174 is no longer indicated.
Question - Is the passenger side Bank 1?

If it was Summer, I would tackle the gaskets myself, but since it's cold in my garage I may take it to the shop. Is $1,200 - $1,600 a good estimate for a shop to fix?
What is the level of urgency for this fix? <25 miles, <100 miles, <500 miles?

Thanks Hamfisted and whtbronco for your input.

 

[riphip]

Before I spent that kind of $$$, I would check/replace any/all rotted vacuum hose, hose assemblies, PCV & hose & elbows that look rotted or feel spongy. Does not cost near the gasket replacement but will need to be performed especially if nothing has been done during that 154k miles. I replaced most of mine for under $200 and a little grime on my hands (use Nitrile gloves). Go to www.rockauto.com
I do not know the current discount code but someone else may chime in. There is a vacuum assy behind the battery also. Heat and age are terrible on these vacuum lines/hoses.

 

[Kenerator]

Thanks riphip. Many of the hoses, elbows, and the PCV have been replaced. I specifically looked for smoke behind the battery. As far as I can tell the vac/evap systems are intact.