2006 Chevy Trailblazer Code P0171 bank 1 lean Hard Starting

Question:
I'm getting the the code Po 171 bank 1 lean so I'm sure it's that air solenoid valve. But would that problem also create a hard start periodically after it's warm? Starts fine after sitting 5-8 hours say. But if I stop at a store & get back in it 10 minutes later she's just spins like for ten -15 seconds, then if I turn key off & right away try again it starts. Doesn't do it all the time but too many times.

Answer:
First of all the P0171 lean code may not be related to a faulty A.I.R. valve on the passenger side of the engine in your 4.2L straight six cylinder in your Trailblazer. When that valve fails it will usually give you a code P0410. It is possible but not the most likely cause of this code.

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A more common problem for a P0171 lean bank 1 and hard starting is a vacuum leak. This engine is known for the intake manifold bolts coming loose and causing a vacuum leak with a hard start condition. With a warm engine the manifold expands and comes away from the gasket. If you look through the drivers side wheelwell you will see bolts that hold down the black plastic intake manifold to the side of the engine. They are all 10mm headed bolts. They are in a center line from the front to the back. The rear 2 are a little difficult to get to. A swivel socket is your best bet to get them. Tighten them all down, clear the codes and give it a test drive.

A way to test for this condition is to spray some brake cleaner around the intake manifold with the engine running. Be sure to stay away from any ignition source since this is very flamable. If there is a vacuum leak, you will notice the engine idle increase a little. You could also see this this on scanner data as 02 sensor changing to full rich. This vacuum leak test can be done on any vehicles engine when a vacuum leak is suspected.

Another possibility is a weak fuel pump. Cycling the key once or twice will help build fuel pressure to the proper level and let the engine start. This will normally give a hard start on a very cold engine, but could also cause your hot engine starting issue and sometimes coe P0171 lean. You would need to install a fuel pressure gauge on the schrader valve and watch the fuel pressure as you cycle the key a few times to see if it slowly increases. If it does you would need to replace the fuel pump inside the gas tank. There is no external filter to replace or casue this issue.

A faulty oxygen sensor if also a possiblity. When they fail the sensor will either give an innacurate reading or will be fixed and not fluctuate the readings as it should be according to how the engine is running. This could be seen using a scanner and watching a live data stream.

These issues apply on the Chevy Trailblazer and the GMC Envoy with the 4.2L engine.


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