Lean codes keep coming back - need help

[stephenkirsh]

So I've had lean codes for a while, 0171 and 0174. Extra symptoms:

- Rough idle when starting the car for the very first time in the day.
- SES lights only come on within the first few miles of driving, aka, when the engine has yet to fully warm up


Work I've done:
- ccv
- spark plugs
- valve cover gasket
- lower and upper intake boots
- replaced vacuum plugs
- swapped MAF from my dad's 330 and rough idle was still there
- VANOS return line

Haven't smoke tested it yet, but here's my fear. Since the problem only happens when the engine is cold, driving it somewhere will warm it up and seal the leak.

Any ideas at this point? I'm running out of ways to fix this.

[danewilson77]

Throttle body gasket, or disa gasket leak? Intake gasket?

You're looking for un-metered Air flow, and it looks like you've taken care of a majority of them.

Continue throwing darts or complete a smoke test.

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[stephenkirsh]

Throttle body was recently inspected (last week) and it all looked good.

DISA gasket is very possible.

What's the intake gasket?

[kayger12]

Check the vacuum lines from the secondary air pump.

If you're good there move on to the DISA gasket.

[stephenkirsh]

Isn't the secondary air pump exhaust related?

[kayger12]

Isn't the secondary air pump exhaust related?

It is. It feeds air to the cats during cold starts, but iirc it is connected to the intake manifold via vacuum hose as the pump is actuated via a vacuum powered check valve.

If you're only getting the condition during the first cold start of the day it points me to the SAP as it only operates during cold starts (not subsequent starts on an engine that has some leftover heat in it from being run earlier).

There's also a code for the SAP being bad, but I think that involves a bad check valve or the pump not working. Not sure on that.

[danewilson77]

What's the intake gasket?

The gasket for the plenums.

[stephenkirsh]

Ugh that looks nasty.

Looks like there's a million more options still. I guess I just need to do a smoke test.

[danewilson77]

Yes. Looks like you've fixed most culprits. Could maybe replace disa o-ring and look at SAP as KG mentioned. Both are cheap. Beyond that though, smoke is your friend.

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[kayger12]

In case you need it.


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