Please help--recurring trouble code, rough idle, misses


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Please help--recurring trouble code, rough idle, misses,

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entropy333
New User

Jul 22, 2020, 9:48 PM

Post #1 of 3 (960 views)

Please help--recurring trouble code, rough idle, misses,	Sign In

2008 Hyundai Santa Fe 2.7 l. runs rough, check engine light on, code po300, has had plugs, coilpacks, plenum gasket, fuel injectors replaced. Also intake plenum, crank sensor, mass air flow sensor, fuel pumo, filter and regulator, and computer PCM and throttle body.Timing belt and ignition wiring checked, vacuum lines and compression checked, also leak-down tests. After part replacement, car runs okay for a couple minutes, then engine light comes back on and P0300 code returns.Please help--don't know what else to try, thanks.

Double J
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Jul 22, 2020, 10:39 PM

Post #2 of 3 (950 views)

Re: Please help--recurring trouble code, rough idle, misses,	Sign In

Well you've thrown a lot of parts at this, i assume all in an attempt to fix the P0300

Quote

After part replacement, car runs okay for a couple minutes,

after which part? any in particular or after all were replaced?

Have you checked the Lower Intake manifold gasket for vacuum leaks?
I didn't see where that was replaced,only see the Intake plenum and gasket...

(This post was edited by Double J on Jul 22, 2020, 10:41 PM)

Sidom
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Jul 23, 2020, 9:59 AM

Post #3 of 3 (920 views)

Re: Please help--recurring trouble code, rough idle, misses,	Sign In

a P0300 is a random misfire code. This pops up when more than 1 cyl is misfiring. 1st it would help to find out which cylinders are misfiring.

If it runs good while it's cold, you need to do the compression test while it's warm and running bad.

What was the results of the compression test and leak down test?

Is there any P0171/P0174 codes stored?

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