Rough idle when waiting at lights

magicmike · Post by **magicmike** » Fri Oct 15, 2004 2:39 pm

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

vrg3 · Post by **vrg3** » Fri Oct 15, 2004 2:54 pm

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.

Post by **Legacy777** » Fri Oct 15, 2004 3:46 pm

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

magicmike · Post by **magicmike** » Sat Oct 16, 2004 7:10 pm

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

vrg3 · Post by **vrg3** » Sat Oct 16, 2004 7:16 pm

The former. Unplug the connector, reset the ECU, and then drive around to see if the car behaves any better without the sensor.

entirelyturbo · Post by **entirelyturbo** » Sat Oct 16, 2004 8:49 pm

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...

evolutionmovement · Post by **evolutionmovement** » Sun Oct 17, 2004 5:58 am

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

biggreen96 · Post by **biggreen96** » Sun Oct 17, 2004 6:26 am

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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Rough idle when waiting at lights

Rough idle when waiting at lights