2004 Ranger Edge 3.0 156,000 miles - I helped my step-son put a reman engine after the cam synch shaft went out. Not being too familiar with this set up I(we) didn't know what the alignment tool that came with the new shaft was for and it got lost/ thrown away during clean up after engine install. Anyway got it in and running but runs rough with po171 lean bank 1 code. Here's what I've tried :

brought #1 cylinder up and aligned tab on shaft to center of opening on shaft housing. It was off about 90 degrees from where I had thrown it in but didn't help ran the same.

Checked exhaust manifold temp to narrow down cylinder was the issue, found cylinder #1 had low temp compared to others so started there. With it running pulled wire off the injector which made no change so checked injector pulse with a noid which lit up so that lead me to think bad injector. Replaced it with no change. Tried pulling wire from #3 and engine ran worse so moved to #5 and pulled wire with no change. Moved new injector from #1 to #3 and #1 still made no change when pulling wire off and #3 did again.

The other possibility I understand is that there's an intake leak.

We also replaced the coil we found was bad after the new engine install.

What can I do/ check before pulling the intake?

 

Welcome to the forum

Lean on one bank/side of an engine means computer is opening injectors on that side more than it "thinks" it should from the air flow it is getting from the MAF sensor.

O2 sensors read oxygen level in the exhaust, too much oxygen means Lean too little means Rich.
So O2 sensor on Bank 1 was showing too much oxygen in the exhaust, so computer added more fuel and it still show too much oxygen so computer added more fuel, and...........
Computer continues to add more fuel and then reaches a preset number at which time it will set the Lean code for that bank, it continues to add more fuel.
The CEL and code are to give the driver a "heads up" that something is wrong.

The misfire means no oxygen was burned in that cylinder so it all got dumped into the exhaust, and that in itself can cause the Lean code.

Easiest way to check fuel injectors is to unplug the coil pack wires and crank the engine a few times then pull out spark plugs, dry one would be suspect for injector issue.

For lower vacuum leak start with cold engine.
Loosen and remove fan belt from crank pulley
Start engine
Spray Quick Start or Carb cleaner around lower intake and fuel injectors on that side.

Also check upper intake, both banks could be close to pre-set limit for Lean code but only one bank is over it.

You can run a cold engine for 2 minutes without water pump or alternator, but no more or it could over heat.
Running engine without fan blowing makes things much easier.

Cam synchronizer is timed with #1 cylinder at COMPRESSION stroke Top Dead Center, so you can't just put crank on TDC mark, this is a 4-stroke engine so each cylinder has two TDCs, compression and exhaust.
So to time the synchro unit you need to make sure which TDC #1 is on