Steady Check engine light and rough idle

[Tippets]

Just finished replacing the water pump and corresponding coolant system items. Went on a road trip and the check engine light flipped on 180 miles in. Pulled over and turned the car off and cranked the lid off on the gas tank. The engine starts no problem but it has a rough idle. No smoke or bad smells... any ideas? 2011 LR4 152,000 miles, service is up to date. Hopeful I’m going to be able to drive it back home.

 

[greiswig]

Hard to tell without codes to interpret, but I’d start with the simple assumption that something you unplugged to get all that work done did not get plugged back in right.

 

[jlglr4]

Agree - if you can find a local autoparts store, they likely have a generic code reader you can use. Rough idle with no other problems could be a vacuum leak - maybe a breather tube popped off. Could also be a coolant temp sensor is disconnected, or the MAFs or MAP sensor.

The other common problem that causes a vacuum leak is the PCV diaphragm. If you’ve never changed it, that’s also a likely candidate here, not that it has anything to do with the work you did unless you maybe inadvertently knocked that little round cover loose. Easy fix, but don’t pop it off until you have the new diaphragm and cover in hand - the tabs on the cover snap off, so you’ll need the new cover to put it back together.

 

[Tippets]

Here are the codes it threw:
P0101
P0108
P0171
P0174
P0850
P050e
P0300

Diagnosis from this mechanic is replace the PCv, my mechanic 300 miles away says it is fine to drive around and just get it fixed when I return. Any other red flags?

 

[jlglr4]

P0171 and P0174 are the lean codes - bank 1 and 2. These are the primary codes you see with a faulty PCV (or any vacuum leak).

P0101 relates to MAFs - I can see this being related to the vacuum leak if the computer is trying to match the MAF signal to the air it’s sensing at the cats.

P0300 - this is a misfire code - likely related to the PCV - lean condition causing misfires = rough idle.

The other codes, I’m not sure - maybe old codes that were never cleared? Here they are:

P0108 relates to MAP sensor - not sure why this would be affected by the PCV.

P0850 - this is a transmission code. Again, no connection to PCV that I know of.

P050e. - Exhaust temp at cold start - no idea.

 

[ryanjl]

I'd start by making sure you reinstalled the intake plenum correctly.

 

[greiswig]

Agree with intake plenum or hoses. Might be a coincidence that your PCV valve failed right after doing this work, but probabilities would lean toward not.