Gents: struggling (as always) due to my lack of mechanical /diagnostic skills. I’m lean on both banks. No other codes. Car doesn’t seem to drive poorly. I’m due for an inspection though and I can’t seem to find the problem so Turning to you for some help.

Here is is what I’ve done thus far.

Visual check for leaks
Smoke test (diy rig that did smoke, but I started guessing that it made enough smoke when I didn’t see any smoke, because I was SURE I’d find a leak. )
Air filter
Fuel injector cleaner -gas tank
OTC fuel injector cleaner into the rail
New plugs -
New coils -
Car wash

2/3 02 sensors were replaced two years back or so - he had issues with 3rd.


Including a pic of the last bill I got - where he notes which sensors were replaced. He was able to pass me, and the check engine light stayed off for a considerable amount of time. It’s part of the riddle, I suppose.


https://imgur.com/gallery/KciQ4ky



I feel bad throwing parts and my time at it - but frankly my experience at the dealership isn’t any better.


What else can I /should I be checking out ?


As always - appreciate your help.

 

There are four O2 sensors. Two upstream and two downstream. Downstream would have no effect on any codes for lean, only upstream which have a major roll in the air/fuel ratio (and thus economy, etc).

A lean code is caused by excess of air for which the computer can no longer adjust. Possibilities include MAF sensor (you can clean it with spray, dont touch the wires inside). Bad EGR valve (the it fails, its like a HUGE vacuum leak). A crack in the intake pipes, often near the metal bands. A bad throttle body gasket. A dirty throttle body. Leak at oil cap or its stem base at the valve cover. A leaking oil dip tube.

 

You give me hope. Thanks. Have cleaned throttle body, replaced MAF... but will have a look at some of this other stuff.

Focus on engine bay and not o2/cats/exhaust ? Sorry if that’s a dumb question.

 

Is this not a petrol engine so should not have the EGR problem or intake pipe problem

 

While the engine is running spray brake cleaner or starting fluid around all air intake areas and listen for a change. If you get a change, that is where your leak is.

The oil filler stand pipe is a known area for leaks at the o ring on the valve cover.
Good luck

 

Thanks. Have ordered a filler tube as mine is in fact old and seems cracked.

This is the freeze frame data. Anyone out there to interpret for me ? I just don’t understand fuel trims :/

https://imgur.com/gallery/wrbgAud

 

To me, the only thing I would look at is the short term fuel trim. I would think it would be similar like the two long term ones are. But there again someone with more knowledge will be along soon

 

Man I have the lean codes as well. No other codes. I think my EGR is failed, but wouldnt I get other codes?

 

Just silly to throw parts at it so hoping someone will
come along to see something in that data to suggest what’s going on.

 

Did you spray brake cleaner around the engine looking for the leak? Do you have access to a smoke machine?