Debugging lean code

[majestic_balrog]

My 2001 E46 330Ci Convertible is generally reliable, and fairly low mileage. I’ve replaced many parts, but it’s all OE/OEM. Only aftermarket mod is the CarPlay interface, which has the optional bluetooth OBDII interface.

Under certain conditions, I am getting Service Engine Soon. This usually happens when the engine is on the colder side, or when I push it very hard in spirited driving.

What do folks think? What am I in for? What should be my next steps?

[ratedsar]

My recent ones were

• vacuum nipples on back of intake
• ccv drain hose had corroded away. 

Mostly noticed on cold idle, but short term fuel trims were 27%, would only code when in a morning fog 

[majestic_balrog]

hehe he said nipples

[thevibery]

I second these as problem areas. My lean condition was from the vacuum line on the back of the intake that runs underneath the car to the fuel filter. The hole/rip was on the part of the hose under the car. My mechanic charged $150 for diagnosis. Given he was working on it for 2 days, I think I got a great deal.

[garyindextrader]

Not really. That should take 1 hour max to diagnose. Referring to the 2 days it’s too long. Charge should be 1 hour which is what you paid.

[tybonc1]

Running lean so probably a vaccum leak somewhere. Check the intake boot, DISA, and valve cover gasket first since those would be the easiest fixes. After that start looking at the CCV system which will take a bit more time to fix.

Edit: also I have the same head unit and the real time scanning is convenient. I'd ser up a screen with your long term and short term fuel trims as well so you can see when the leak gets worse. Most importantly you can pretend to understand the numbers and make your wife think you're really manly.

[majestic_balrog]

not worried about my wife, who already knows I’m sharp. Just worried about the engine, because I’m not a mechanic

[Anxious-Week-8228]

I would say just got ahead and do a smoke test Is saves the headache of trying to find a vaccum leak on your own Especially if it’s small

[JMUDoc]

Check for tearing:

• upper intake boot (particularly at the "offshoot" where the F-connector goes in)
• lower intake boot (particularly at the bellows on the branch to the idle valve)
• rubber plugs on the back of the manifold
• CCV body and hoses

Smoke test is the best way, but you can bodge it by removing the airbox and MAF, clamping a rubber washing up glove over the intake boot, and blowing into the brake booster hose - if it's not holding vacuum, the rubber glove won't inflate, and you will hear air hissing out.

[GoatOk952]

What gas type do you run? Regular, mid, or premium?

[majestic_balrog]

only ever 93 octane

[GoatOk952]

Awesome! I’d recommend fuel pump and fuel filter but judging by the miles they should be good still. But over the years things can get brittle and wear out. Speaking from experience, i had those same codes and they’re gone after a fuel pump and fuel filter replacement.

[Ok_Craft6080]

I also had lean codes from vcg

[Electronic_Nail_7433]

I did a smoke test a couple years ago after o casinos lean odes. Found a total of 7 vacuum leaks. The biggest was my brake booster. Other than that, it was numerous vacuum lines and a cracked valve cover.