2006 2.3L is running rough at idle, rarely will stall at intersections, but this is my 17yo son's ride & I'm afraid this is dangerous for him. OBDII codes are P0171 and P2195. Best mileage is 21mpg, driving very conservatively. Ordered a new Bosch Heated O2 sensor, checked resistance. Old one was faulty and installed new one. Sensor wires look OK but I cant trace them all the way back. Ck engine lite came back on, same codes, same rough idle. Then carefully removed MAF sensor and cleaned it with the $10 can of MAF cleaner. Did not resolve it.

I am trying to check the vacuum lines for a leak, but am having problems identifying them, even with the Haynes manual. Any tips?

Also found this cover laying on a line below the battery. Any clues what it is and where it belongs? (see pics). Googled numbers on it to no avail.

Thanx in advance

 

Realized plastic cover is for outlet on fuse box. Pops right on. Idle sure is horrible tho.

 

So it could be the PCV. Is there a way to test w/o removing wheel, fender well, &breeather plate from block? This has to be done every 12K? Really?

 

2.3l DOHC Duratec engine is what you have.

There is a common issue that comes up with these, a rubber plug comes out of the front end of the intake, behind power steering pump.
Causing those codes and rough idle.

You can test for this issue by spraying Quick start or carb cleaner at that location and see if engine RPMs change indicating air being pulled in to engine.

Google: 2002 ford ranger 2.3 intake manifold repair

There are videos on location and repair for this issue.
I think you can just remove/move Power Steering pump for access, but not sure on that.

 

Bit the bullet and took to dealer for diagnostics. They are sure it is a vacuum leak "under the runners of cylinders 3 & 4". Mechanic said this is common for this year engine. Quoted $640, mainly labor, to pull intake manifold & replace vacuum parts. Mechanic said once I get the intake manifold off, it will be obvious. Parts quoted at $156: valve assembly, tube, tube assembly, and the 4 new intake gaskets. Needless to say, I will do it myself. Diagnostics was the difficult part for me. Gonna look at manifold gaskets, wouldnt think I would have to automatically replace them. Anyone heard of this problem in a 10 year old 4 cyl ranger?

 

Not sure if it is common but certainly has happened on other 2.3l duratecs

This thread might be helpful: https://www.ranger-forums.com/2-3l-2...lation-144280/

Lots of pictures

 

Brian just posted this a couple of days ago. Great information.