When I made this post I have no SES light or pending codes after changing out my MAF (I had P1171/P1174 before that).

they came back while driving this weekend and I strongly feel they are the cause of the vibration at idle.

I had made a post a few weeks ago about the lean codes, here it is:

https://landroverforums.com/forum/di...-p1174-100897/

 

Lean codes will do that. I should have clarified in my last post, I did not have “o2” codes, I had lean codes. The lean codes came from the o2 sensors reading higher then normal, not alternating. Truck thinks it’s getting way too much air, and as a result dumps fuel in to try and correct the mixture.

You could probably confirm this with a funny smelling exhaust, and the exhaust tip having black gunk all around it, and I even had black soot being shot out even at idle.

Anyway, lean codes means you are getting unmetered air coming in somewhere before those 02 sensors. You already checked for vacuum leaks and changes the MAF. I would just look up on the forum and confirm you are getting normal readings from the MAF at idle and under load, etc. Make sure all your hose fittings are right and tight. And that’s pretty much all I got for you from a logical standpoint

EDIT: just realized you questioned your fuel injectors, you definitely could be leaking air from there, it is definitely not unheard of. They just slipped my mind. You can try and spray carb cleaner all around that area and see if you get an increase in revs, that would confirm that.

Now from the illogical standpoint, I’ll describe my problem and see if anything applies to you. More information the better I guess right.

My 02 sensors just stop working whenever I go for a splash in some puddles or hose off the engine. I would assume water is getting into the connections and a possible solution was discussed to attempt to hardwire them to prevent water intrusion or put new plugs one the sensors. I believed hardwiring would be easier but after taking a look and how little slack on the wires there are, I don’t think any wiring is gonna be easy so TBD. Anyway this whole deal results in lean codes for me since the o2 sensors stop alternating and sit around .5 to .8 and then starts dumping gas and vibrating at idle because of a super rich mixture even though it still thinks it’s lean ¯\_(ツ)_/¯

Your o2 sensors seem to be working fine which puzzles me but I’ll tell you what I did so we can probably both lose are minds at this ghost of a problem.

Checked for vacuum leaks—no leaks—still got lean codes

Checked for exhaust leaks—a few leaks—rewelded everything, even put a new exhaust manifold—still got lean codes

Checked MAF activity—same as everyone else—still got lean codes

Checked o2 plugs for water and cleaned out using electrical contact cleaner—no water and all clean— still got lean codes

Another EDIT: I also swapped o2 sensors to try and isolate the problem and rule out a faulty o2– same readings no matter which sensor is used—still got codes

Checked for vacuum leaks again using a homemade mineral spirits smoke gun—no leaks found—truck magically starts working

As you can see, no logic whatsoever.
only guess I got is adding even more fuel did something and then my O2 sensors started working and then I’m on my marry way.

This whole ordeal for me lasted 3 months of 10-11mpg, as soon as it fixed itself I started getting 13-14 again and it is much nicer I will say.

Last comment before I end this massive post, just trying to give as much info as possible for you. The problem has reoccurred since then after I go in a puddle like I said, but has started working within a few days unlike the original 3 months. I just did some work and got brake cleaner on the connections and now it’s back and hasn’t left yet, so my money continues on it being a o2 wiring problem although that doesn’t explain how I cleaned the connections several times and still didn’t fix my problem.

Hope this helps somewhat!

 

Sometimes, if there are a bunch of rubber chunks missing, then it's time for a new one. A few cracks in the old rubber don't really seem to cause issues

 

I would pull each spark plug connector one at a time.
If there is one not showing a noticeable increase in vibration, that cylinder needs attention.

 

@XRAD I have no doubts the balancer could be the issue, but after the Lean Codes came back, I suspect that to be the primary problem. They have been there the whole time, just masked by putting on a new MAF and resetting codes.

@Externet good idea. I will try to take the time to do that this week. Other than rough idle and poor MPG the motor runs good and pulls hard. Uses no coolant, uses a normal amount of oil. Low mileage P38 block. New plugs and wires as well.

 

I you have any interest in what my O2 sensors are reading on the UG here is a YT playlist with three videos:

​​​​​​https://www.youtube.com/playlist?lis...4MuQ8-EcM80dKZ

 

Very helpful @Old Bertha. I would not be surprised if my issue is similar.

Since the motor was out of the truck before I bought it (for HG's and motor mounts) I think it's most likely something was not put back together perfectly and there is a small leak. I have installed a new MAF, had it checked for exhaust leaks, tightened up every hose clamp possible, etc.

Something I did notice when tightening up hose clams: The Hose for the IACV going back into the manifold (passenger side hose for the IACV) has a little piece of pipe that the hose clamps onto. That has broken and comes out with the hose when you pull it off. I tapped it back into place, but I think it is very possible that is one source of a vacuum leak. I want to test further to try and avoid an unnecessary repair, but that could very well be it.