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Old 11-06-2019, 09:14 AM   #1
MKE325
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Lean codes, how worried should I be?

Looks like you can't swing a stick without seeing a post about P0174 and P0171, and I hate adding one more, but I haven't seen this question addresses... How much do I really need to worry about these codes? If I wait until Spring to dig in will the engine fall out of my car?

Bought my 2001 325i convertable last month. Drove it 2000 miles to Boston and back, lean codes have started to show up and come back within a week of my clearing them...
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Old 11-06-2019, 09:27 AM   #2
77'911
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On our car, the last part that killed off the pesky lean codes, was the DISA. One reason to have some concern, if it is the DISA, you don't want the metal pin falling out into the engine. I caught ours lying in the intake(whew) just in time. FYI. Might just be a CCV or associated pipe/vac hose. Having said that, after getting rid of the DTC's on our car, the performance and mpg went up.
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Old 11-06-2019, 09:52 AM   #3
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It can also prematurely wear your cats which are expensive.
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Old 11-06-2019, 10:31 AM   #4
MKE325
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Nice call out on the DISA, I'll take a look at that.
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Old 11-06-2019, 12:14 PM   #5
DaveDammit
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Not saying that you shouldn't fix your car, but I have had 171/174 codes for the past 5 YEARS that I haven't solved. I carry a OBD reader and clear the codes when it starts running rough. i think you'll be fine until spring.
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Old 11-06-2019, 12:23 PM   #6
33OCI818
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Quote:
Originally Posted by 77'911 View Post
On our car, the last part that killed off the pesky lean codes, was the DISA. One reason to have some concern, if it is the DISA, you don't want the metal pin falling out into the engine. I caught ours lying in the intake(whew) just in time. FYI. Might just be a CCV or associated pipe/vac hose. Having said that, after getting rid of the DTC's on our car, the performance and mpg went up.
regards
very true. I just replaced the Disa last week. it started out with SES turning on with lean codes then loud grinding noises coming out from the engine bay. Replaced DISA and problems haven't comeback .
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Old 11-06-2019, 12:45 PM   #7
BobC63
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Before looking at the DISA, do a vacuum smoke test. Find it on YouTube (e46 smoke test). I did the "cigar" test; cost me under $10 for everything to do the test - and it 100% worked to find all vacuum leaks.

I found 2 small leaks; fixed them for under $25 - and my 330ci vert has been "code free" for almost a year now.

Plus, if it IS the DISA... it's going to be leaking vacuum (smoke)... so good way to rule it out (or in) as a cause / the cause... before your spend $50 -$100 on a new DISA that you may not even need.
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Old 11-07-2019, 09:14 AM   #8
MKE325
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Great responses! Thanks!
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Old 11-07-2019, 09:56 AM   #9
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Quote:
Originally Posted by MKE325 View Post
Looks like you can't swing a stick without seeing a post about P0174 and P0171, and I hate adding one more, but I haven't seen this question addresses... How much do I really need to worry about these codes? If I wait until Spring to dig in will the engine fall out of my car?

Bought my 2001 325i convertable last month. Drove it 2000 miles to Boston and back, lean codes have started to show up and come back within a week of my clearing them...
You are talking fuel trims. They are not going to get better on their own but that doesn't mean they are going to continue to grow exponentially. They may settle down they may not. But if you are getting codes they are clearlt at a point where teh DME thinks it is problematic and needs attention. You could scan the trims weekly and see how they are trending. If they are stable then wait until the weather gets better and put up with the poor performance.
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