Weird Rough Idle - Subaru WRX Forum
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#1 Old 08-06-2008, 01:38 PM
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Weird Rough Idle

So lately i notice my car shaking while idling at stop lights or in the driveway, popped the hood and noticed the motor shaking a lot while idling. Trying to figure out what would cause this. I changed the plugs in june because i was getting some backfiring when shifting normally and especially when shifting under boost situations along with my friends telling me flames were shooting out the tailpipe. When i changed the plugs i noticed that they were 1 step colder plugs with a larger then stock gap. As soon as i changed the plugs the backfiring ceased and the car ran very very good. But now this idle problem has arose. The plugs i put in were stock gapped ngk and i cant remember if they were iridium or platinum, i'm going to lean toward the iridium ones. But im unsure... any ideas on what may be causing this.. I also noticed the so called "tick of death" which isn't really a deathly sound there sometimes.. and sometimes not there..but sometimes very pronounced. Anyone got any ideas where to start? Probaly going to pull out a plug today and see for sure what they are and how it looks. I did have a small vaccum leak before the turbo that i recently fixed but never reset the ecu, maybe i should try that first?
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#2 Old 08-06-2008, 01:49 PM
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yeah reset the ecu it is possible the car is in limp mode..i have heard of rough idleing scenarios with limp mode
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#3 Old 08-06-2008, 02:35 PM
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I dont know what the signs of limp mode would be but it seems to drive the same..cept while at a stop sign or light the car kinda shakes with the idle, it hits the same amount of boost. Although sometimes it seems like it should get up and go a little faster and doesn't. Maybe its the plugs hmm i gotta find my receipt for them or something, taking them out is such a pain in this car.
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#4 Old 08-06-2008, 02:35 PM
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the CEL is on during limp mode

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#5 Old 08-08-2008, 09:25 AM
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No CEL at all , I reset the ecu and noticed the positive cable connecting to the battery was very loose. So loose that when i popped off the negative and went to move the battery the positive just popped off on its own. So I reconnected both and tightened them down really good. Car seems to respond better no more light dimming when i let off the accelerator, but the idle still seems a little shakey. Im going to run it for a while and let the ecu relearn after a full tank see if it gets any better. Also i kind of noticed it happens more often when its hotter out.
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#6 Old 08-10-2008, 04:31 AM
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so the plugs that were in the car before you changed them were 1 step colder? was the car tuned on these plugs? do you have a bov? these have been known to make cars run rich between shifts that could cause backfires or flames. what are your mods? it would help to know them all.
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#7 Old 08-11-2008, 07:07 AM
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No BoV , no i dont think the car was tuned to 1 step colder. The gap on the colder plugs was fricken huge compared to stock. These are my mods, AP stage 2 as far as i know.
Walbro 255 fuel pump
TurboXS uppipe
Invidia V3 downpipe
Invidia 4" Titanium tip catback
TurboXS TMIC
K&N air
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#8 Old 08-11-2008, 05:56 PM
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Hi everyone im new to the forums here!! Just bought my 07 blue pearl WRX a few weeks ago!! I love it so far....Im anxious to hear what people have to say about your question. I feel like im having a similar issue. It seems to shake at an idle as you were saying. I am running stage 1 91 octane and that is my only mod. It was doing it a little even before the AP. I took it to the dealer before I flashed stage 1 and they said there was nothing wrong with the car. I think im hearing a ticking sound as well but the dealer said it was my injectors??
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#9 Old 08-11-2008, 08:30 PM
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Quote:
Originally Posted by oldspower71 View Post
Hi everyone im new to the forums here!! Just bought my 07 blue pearl WRX a few weeks ago!! I love it so far....Im anxious to hear what people have to say about your question. I feel like im having a similar issue. It seems to shake at an idle as you were saying. I am running stage 1 91 octane and that is my only mod. It was doing it a little even before the AP. I took it to the dealer before I flashed stage 1 and they said there was nothing wrong with the car. I think im hearing a ticking sound as well but the dealer said it was my injectors??
Go test drive a new one. Boxer motors tick and rumble at idle to a limited extent and this is normal. It shouldn't be worse than a new one though.

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#10 Old 08-11-2008, 10:03 PM
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The gap in your plugs shouldn't change just because they are a different type. I believe the safe zone is .38 to .42 with our cars. Those "pregapped" plugs are usually all different. I've pulled one plug out of the box that was gapped correctly. I'd check the gaps if I were you.

And thanks for reminding me, I looked up the gapping to double check for you, and I gapped mine all at .34 when I finished my rebuild. I'm sure that's not helping anything.
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#11 Old 08-11-2008, 11:51 PM
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Quote:
Originally Posted by mosc View Post
Go test drive a new one. Boxer motors tick and rumble at idle to a limited extent and this is normal. It shouldn't be worse than a new one though.
Thanks thats a good idea ill give it a go.
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#12 Old 08-12-2008, 10:18 AM
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Should be considered WR blue mica paint though.....being severely off topic, sorry. But, Yeah don't know about scythenkai, but oldspower its probably what mosc said. The boxer idle isn't as smooth as most engines. So, give that a try. The boxer might just be different then what your used to sound wise.
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#13 Old 08-13-2008, 08:56 AM
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It doesnt seem so ruff now , but it has been colder lately. Im just starting to think its normal. Although i was standing there with my dad and talking to him about it while watching the engine idle. It seems to shake when the idle changes you can tell the idle changing because of the sound coming from the exhaust. Maybe something is draining power making an idle change. Or possibly i need to set the idle higher.. is there some way to do this on the wrx's ? like a throttle screw. Im still trying to adapt to this new type of engine. Used to honda inline 4's

Quote:
Originally Posted by Chase View Post
The gap in your plugs shouldn't change just because they are a different type. I believe the safe zone is .38 to .42 with our cars. Those "pregapped" plugs are usually all different. I've pulled one plug out of the box that was gapped correctly. I'd check the gaps if I were you.

And thanks for reminding me, I looked up the gapping to double check for you, and I gapped mine all at .34 when I finished my rebuild. I'm sure that's not helping anything.
I checked the plugs i put in were ngk iridiums all correctly gapped to .38 or .39 , i remember checking them when i put them in. But with the iridiums you can't gap them because of the iridium tip. The old plugs were an outrageous .45 or .46 if i remember i tossed em out. Im due for an oil change. I am going to get that done soon along with a complete tranny fluid change to uncle scottys coctail and change the rear diff too. So ill see if this makes any difference. Going to check that banjo bolt filter thingy too while im at it. Don't know when i am going to get at it though hopefully before the end of the month ill let you guys know how it goes

Last edited by mosc; 08-13-2008 at 10:03 AM.
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#14 Old 08-13-2008, 09:03 AM
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Last edited by mosc; 08-13-2008 at 10:04 AM.
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#15 Old 08-13-2008, 06:40 PM
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the fuel pump burned up the fuel pressure regulator....your prob running super rich. that could also be why you were/are backfiring
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