Rough idle when waiting at lights

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magicmike
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Rough idle when waiting at lights

Post by magicmike »

When the car is in park it idles fine (aprox 800rpm) when its in drive and I'm stopped at a light or whatever the rpms drop down to like 5 or 6 hundred and the car feels like its shaking a bit. My civic used to do the same thing when it got up there in mileage. I'm thinking its the o2 sensor. Everything else is new. New air filter, fuel filter, plugs and wires. I tried a search but only found advice on changing all of the things I just described as new. I'm thinking its the o2 but I dont know. What do you all think. its a rebuilt engine so it should be running smooth I thought ;)

-Mike
-Mike

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vrg3
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Post by vrg3 »

There's a quick check you can do to see if it's the oxygen sensor. Unplug the sensor, reset the ECU, and see how it does. If the problem persists, it's not the oxygen sensor. :)

Is there a chance that you have a small vacuum leak? You could do the starting fluid check.
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Legacy777
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Post by Legacy777 »

Mine does this occasionally.....I think I need to clean up the IAC valve again.
Josh

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magicmike
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Post by magicmike »

do you mean to unplug the sensor and leave it unplugged perminantly? or unplug it, reset the ecu then plug it back in? I'm confused

Thanks,

-Mike
-Mike

2011 Infiniti G37x Sedan - Current
2007 Ducati 800ss - Current
1994 Subaru Legacy Sport Wagon (White)
1994 Subaru Legacy Sport Wagon (Silver)
2003 Infiniri G35
1998 Infiniti I30t
1995 Honda Civic DX
1987 Subaru GL Wagon
1987 Subaru Loyale
vrg3
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Post by vrg3 »

The former. Unplug the connector, reset the ECU, and then drive around to see if the car behaves any better without the sensor.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
entirelyturbo
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Post by entirelyturbo »

I say it's nothing more than a Subaru trait. As most of you know, I've replaced damn near everything I possibly can in the hopes of fixing the bumpy idle. I've replaced the IAC valve with a brand-new one, I've swapped throttle bodies, MAFs, this and that.

Fact of the matter is, I've never driven any Subaru at all that had a perfectly smooth idle. Maybe it's just a boxer four trait...
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evolutionmovement
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Post by evolutionmovement »

The last engine I had idled so smooth (but slightly high) you had to put your hand on it to tell it was running. That was up to about 20k before the exhaust valve went.

Steve
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biggreen96
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Post by biggreen96 »

subyluvr2212 wrote:I say it's nothing more than a Subaru trait. As most of you know, I've replaced damn near everything I possibly can in the hopes of fixing the bumpy idle. I've replaced the IAC valve with a brand-new one, I've swapped throttle bodies, MAFs, this and that.

Fact of the matter is, I've never driven any Subaru at all that had a perfectly smooth idle. Maybe it's just a boxer four trait...
did you change motor mounts?
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