# Revs up dan down

**URL:** <https://community.cartalk.com/t/revs-up-dan-down/84292>\
**Category:** Maintenance/Repairs\
**Created:** [March 22, 2014, 11:15pm UTC](https://community.cartalk.com/t/revs-up-dan-down/84292 "2014-03-22T23:15:19Z")\
**Posts on this page:** 5\
**Page:** 2

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**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\
**Post date:** [April 7, 2014, 4:11am UTC](https://community.cartalk.com/t/revs-up-dan-down/84292/21 "2014-04-07T04:11:46Z")

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Are you sure you didn’t tear a crankcase ventilation hose or something, while you were checking out the car?

Or maybe you forgot to reconnect a vacuum hose?

Here’s some other possibilities for P0171 and P0174

Low fuel pressure  
Exhaust leaks upstream of the oxygen sensors  
Intake leaks  
Brake booster hose  
etc.

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**Author:** ![mwkarrick](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@mwkarrick](https://community.cartalk.com/u/mwkarrick)\
**Post date:** [April 7, 2014, 5:04am UTC](https://community.cartalk.com/t/revs-up-dan-down/84292/22 "2014-04-07T05:04:37Z")

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see i never got thouse codes till i replace the old maf…

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**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\
**Post date:** [April 7, 2014, 5:12am UTC](https://community.cartalk.com/t/revs-up-dan-down/84292/23 "2014-04-07T05:12:35Z")

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@mwkarrick‌

Was the new MAF an exact replacement for the old MAF?

Is the replacement MAF a new part, or a rebuilt?

Perhaps the replacement is simply defective

It would explain the P0171 and P0174

The fact that the engine runs well with the new MAF . . . but runs poorly with the old MAF . . . confirms the old MAF was faulty

The fact that the P0171 and P0174 weren’t present with the old MAF makes me think the replacement MAF may be a dud

With all these rebuilt parts out there, it’s not that rare of a situation to run into a bad “new” part

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**Author:** ![mwkarrick](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@mwkarrick](https://community.cartalk.com/u/mwkarrick)\
**Post date:** [April 7, 2014, 5:25am UTC](https://community.cartalk.com/t/revs-up-dan-down/84292/24 "2014-04-07T05:25:32Z")

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the part i got was Remanufactured maf

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**Author:** ![mwkarrick](https://avatars.discourse-cdn.com/v4/letter/m/51bf81/32.png) [@mwkarrick](https://community.cartalk.com/u/mwkarrick)\
**Post date:** [April 7, 2014, 5:27am UTC](https://community.cartalk.com/t/revs-up-dan-down/84292/25 "2014-04-07T05:27:46Z")

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i got it from autozone

[Previous page](https://community.cartalk.com/t/revs-up-dan-down/84292.md?page=1)