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CEL indicating P0171: also weird whine or whistle from engine bay after idling in park for 5-10 min

Tiny
SANTIAD
  • MEMBER
  • 2009 HONDA FIT
  • 72,500 MILES
Random CEL! So I got one a few weeks ago and the car was in limp mode! So I went to autozone and the code was saying cylinder 1 lean (guessing it means lean air rich in fuel) So I checked the air intake and saw it was ok. I took out the KN filter put in the OEM one, disconnected the battery and it went away.

until 2 days ago. This time there was no limp mode but the engine was lacking power and didnt want to rev higher than 3k (i bring her to 4k alot, hence frequent ATF fluid changes). Oo late to go to autozone so I went home disconnected the battery, checked the fuel car (random but I read it somewhere online) waited 30 minutes and the light is gone. I drove her hard yesterday and can say she improved as the day went on but am waiting for it and have no explanation for it.

Somehow I think this all goes back to the big recall for the vtec rocker springs. Possible reasons for a "cylinder 1 lean"

-maf sensor or ignition issue
-fuel system issue
-vacuum leak
P0171- fuel system too lean bank 1 (cylinder number 1 denotes bank 1)

Probable causes:

1) Large vacuum leak
2)Fuel system concern
3)Ignition system concern
4) MAF sensor faulty
5) HO2/AF ratio sensor fault


Things I have done so far.

removed all parts leading to the engine to get a better look at hoses for any punctures or tears and to see if any buckle under acceleration. Nothing but I did notice of the two large hoses leading to the passenger compartment, one was showing wear (I assume that's to the heating core but am not sure). I might replace that going forward.

Still cant get to the bottom of that sound, any advice would be greatly appreciated!
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Sunday, November 6th, 2011 AT 7:46 PM

3 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The sound that you hear appears to be a vacuum leak, get some choke cleaner an spray around intake manifold and throttle plate as well as hoses. If your rpm changes you have found it. Also check yoru fuel pressure as that can cause a code p0171. It was wise to clena teh maf though as the K&N filters are oiled to much sometimes and cause the maf to screw up. You might try cleaning the maf with the choke cleaner as well but make sure it is dry before you start the car. It's very hard for us to diagnose sounds via the computer and if it doesn't go away you might have a pro look at it to give you an opinion. Also make sure all your duct work leading to the throttle plate does not have any holes in it as that can make teh maf work screwy and maybe be cause of your noise as well.
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Sunday, November 6th, 2011 AT 8:26 PM
Tiny
SANTIAD
  • MEMBER
  • 2 POSTS
Thanks for the advice. Some questions though:

1) can I spray choke cleaner in the general area? Also the fit has drive by wire system, can spraying in the area damage it?

2)how to check fuel pressure? Could a failing filter make a whining noise?
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Sunday, November 6th, 2011 AT 9:52 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
No the noise wouldn'tcom efro m a failing filter. The choke cleaner won't do much at all to wire. It willhowever eat paint so watch that you dont' get any on the paint. You needa gauge for the pressure check and it should hook up to fuel rail.
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Sunday, November 6th, 2011 AT 9:56 PM

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