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need help! p0300 code and rough idle

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Old Dec 25, 2011, 08:17 PM
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need help! p0300 code and rough idle

I have a 06 evo9 60k. I've tried searching about the code and found some ppl have problems with aftermarket injectors and incorrect gapped plugs causing it but my car has new plugs gapped at .022 and stock injectors and cams as far as I know. I bought this car wrecked and rebuilt it, just got to drive it for the first time few days ago and this is my first evo. The car idles like it has a set of cams and throws the code at idle, it idles up at around 1500rpm when you start it up and only drops to about 950-1000rpm when at operating temp. It drives fine and pulls smooth on acceleration with no noticeable misfire. I've reset the code and it comes right back on.

Mods are
Greedy full exhaust
Forge bov
Forge mbc
Aftermarket clutch
Injen intake and cold piping
Big fmic
Solid mounts
Turbo timer
Aluminum radiator

Not sure if it means anything but it has a piggyback clip on one of the coilpack wires on the driver side, like its had a tuner or monitor wired up at one time. And some sort of small box wired what looks like to the rear o2 sensor that's under the pass seat. Not sure if it has anything to do with my cel.

Last edited by wekpcle123; Dec 25, 2011 at 08:26 PM.
Old Dec 26, 2011, 09:25 AM
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Anyone?
Old Dec 26, 2011, 10:07 AM
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check all your vac. hoses. mainly egr ones and fpr line. mine use to pop off all the time. tip tie every hose. check under intake manifold. report back
Old Dec 26, 2011, 10:32 AM
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boost/vac leak, bad coils, cas, ... dirty mas?
Old Dec 26, 2011, 11:20 AM
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Turn it off in the tune.

Solid mounts and certain clutches will trip the P0300.
Old Dec 26, 2011, 11:30 AM
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What's a normal idle rpm for my car with stock internals? Im gonna check all my vacc. Lines and check maf. Is there a good way to check coils?
Old Dec 26, 2011, 01:20 PM
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Originally Posted by sdvratrod
It drives fine and pulls smooth on acceleration with no noticeable misfire.

Mods are
Greedy full exhaust
Forge bov
Forge mbc
Aftermarket clutch
Injen intake and cold piping
Big fmic
Solid mounts
Turbo timer
Aluminum radiator

Not sure if it means anything but it has a piggyback clip on one of the coilpack wires on the driver side, like its had a tuner or monitor wired up at one time. And some sort of small box wired what looks like to the rear o2 sensor that's under the pass seat. Not sure if it has anything to do with my cel.
Idle is probably raised if it holds consistent at 1000rpm. Coils are easy, it works or it doesnt so if its not misfiring you are good. I would presume based on your description that it has timing added at idle which also will cause the P0300 to come on in the IXs.

Aaron
Old Dec 26, 2011, 02:49 PM
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Could the timing be changed in a tune, because I checked the belt and all the markings are dead on. Would the car still idle rough if the idle was just turned up in a tune?
Old Dec 26, 2011, 03:14 PM
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not timing marks with timing belt. timing in the ecu
Old Dec 26, 2011, 05:14 PM
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Checked all vaccum lines and all good, coils seem to be working fine and I cleaned the maf and throttlebody and still no change, it idles at 1200rpm and has like a slight miss. I can idle the car up to about 3000 rpm and no miss.

Could someone have changed timing and idle rpm with a handheld because the car doesn't have a tuner on it.
Old Dec 27, 2011, 09:11 AM
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Update: after I did the things stated above the car does not throw the code as quick, I have started it and drove 15miles last night stop and go but still idle at 1100-1200rpm, got in it this morning and started it but car didn't want to idle guessing because of being cold, but after it warmed up it idled back up to 1100-1200rpm and after driving for a few min. It threw the code again.
Old Dec 27, 2011, 09:18 AM
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It can most certainly be fixed in the tune. Do you have access to a cable and laptop? I can fix it in about 40 seconds.

Aaron
Old Dec 27, 2011, 09:27 AM
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I have a laptop but not sure what cable your talking about?
Old Dec 27, 2011, 09:44 AM
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Openport 2 cable-

http://www.tactrix.com/

aaron
Old Dec 27, 2011, 10:43 AM
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Mine keeps coming up with that code aswell, usually a couple times per tank of fuel.
But since I just got a 2.3l rebuild with new injectors, my tuner said its fine because it's still running in, as long as it's a multiple misfire and not a single one.

I get my last tune for the rebuild next month, so hopefully don't get it anymore after that.
I'll let you know how mine goes.


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