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That could come from almost anything; Plastic Vacuum Res and/or Lines cracked, PCV rubber elbow collapsed, Intake Gaskets, torn/cracked Air Cleaner Rubber parts between T/B and MAF Sensor, Hose from the Brake Booster, anything that could bring in un-metered air to the engine...............
I'm thinking the rough idle I have is more to do with either a faulty EGR valve or perhaps the vacuum line is disconnected or damaged... But where is that pesky valve?
Those particular DTC's are almost always solved by checking the plumbing from the PCV back to the throttle body. Typically its covered with a flimsy layer of insulation that can easily hide cracks, splits etc that give lean bank codes.
Not sure if that chassis and engine have IAC valves which if defective could give the rough idle hunting you describe but those typically throw another code---I don't recall if they will trigger P0171 & P0174 at the same time.
HTH---please let us know what you discover and your fix.
Here is a pic with the dog house removed. Can you suggest area to look for PCV?
I tested EGR valve by sucking and it stalls out so that means that's not the issue. There is another similar looking unit with large vacuum off the intake manifold. That one has vacuum at idle. What is this!
Located PCV on right side (from inside van) valve cover.
Pulling on that hose I can clearly here an air (vacuum) hiss that varies as I play with hose. Will need to remove air filter section to see what's what.
Been working on a P0171 & P0174 lean condition for a while and I just found my air filter can has a sloppy large rubber grommet on the bottom side for the IAT/MAF Sensor wires. It's in the right place for an air leak that can throw off the air/fuel mix to cause a lean condition
I've had those grommets out of the filter housing, have always been very careful when re-installing them though. That's great advice and observation Junque!
Most of use who've dealt with those DTC's almost automatically check the PCV>TB fitting--the grommet thing being a bit unusual but still a strong possibility to be at fault too.
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