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Old 04-08-2013, 06:10 PM   #1
Jb2.5rstst
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Default 2005 impreza 2.5rs auto Hesitation/low iddle

So a little history....

Changed the head gasket a few months ago. Car has 153xxx miles on it. After changed the head gasket I replaced sparkplugs but the wires didn't come in yet, so I ran it with the old ones. After a few days the car was misfiring like crazy and would stall out. So I stopped driving it and changed the wires. After doing so I got the famous code p0420. I ignored it at first because I figured since I was misfiring some gas prob got burnt down the pipe and caused the cel. After a few days the code went on and off and the. Went away completely.

Out of no where I started hearing a rattle as I accelerate. Searched on line and others where having a similar issue and most was caused by the shield on the headers. So I took them off. But the noise is still there. I took a mallet and tapped slightly on the cats and they sounded rattely.

Now my idle is very low under 500 and lower...and car shakes when it idles.

What is causing this? I just changed the fuel filter and hoped that it would fix the idle but nothing.

Is it the cat? O2 sensors?

Any help is appreciated.
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Old 04-08-2013, 08:48 PM   #2
kero
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Quite possible a clogged cat that has broken up inside the housing. This would also give you hesitation as the flow is restricted through the exhaust.
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Old 04-08-2013, 09:06 PM   #3
Jb2.5rstst
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Would that also explain the low idle or is that from the o2 sensor ...
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Old 04-09-2013, 09:38 AM   #4
Jb2.5rstst
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??? Bump...


Anyone else have any ideas
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Old 04-09-2013, 12:14 PM   #5
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Exhaust restrictions can def cause idle issues.
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Old 04-09-2013, 01:32 PM   #6
Jb2.5rstst
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One thing I forgot to mention is that the car idles at 499 in neutral and park....but once in gear it goes down ....
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Old 04-10-2013, 11:28 AM   #7
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That is correct, idle will be higher in neutral or park as there is no load on the engine.
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Old 04-15-2013, 09:28 PM   #8
Jb2.5rstst
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I am aware of that however there is hard vibrations and car feels like it wants to stall....is this caused by the cat being clogged or maybe o2 sensor going bad?
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Old 04-16-2013, 01:06 PM   #9
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I would say more cat that 02.
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Old 04-16-2013, 03:54 PM   #10
Jb2.5rstst
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K..well I ordered a set of tsudo uel headers with cat delete...hopefully that does the trick
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Old 04-16-2013, 11:07 PM   #11
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Bump.................
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Old 04-16-2013, 11:07 PM   #12
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Bump.........................
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Old 04-18-2013, 08:08 AM   #13
Jb2.5rstst
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Still haven't received the headers yet....ordered them from semotors.com..originally I ordered the CATLESS ones but they were out of stock do I got the ones with the high flow cat....should come in this week...will update once they are installed
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Old 04-26-2013, 05:53 PM   #14
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Got the tsudo headers...just running the headers and cat pipe right now...getting the exhaust welded tonight hopefully to complete the system...

Still have some hesitation and car feels like it's wants to stall when in park idle as well as when in drive and idleing....mostly when in drive though.....

What can cause this...

Could it be the injectors? No check engine light....

Anyone?????
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Old 04-26-2013, 10:05 PM   #15
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Bump.......
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Old 04-28-2013, 11:42 AM   #16
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Bump....anyone
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Old 04-29-2013, 12:36 PM   #17
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I just changed the valve cover gaskets and spark plugs on my Saabaru. Straight forward, easy job. I go for a test drive and when I come to a stop, the car stalls out. Restart and very low idle. This happened multiple times on my way home. Got back to the house, rechecked everything and found that one of my hose claps weren't tight enough on the intake pipe. Tightened it down and fixed the idle issue.

Could your problem be an air leak like mine?
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Old 05-01-2013, 02:52 PM   #18
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I wouldn't be surprised that I have a small leak by the intake cuz my stock box is a little messed up....will be doing the hybrid intake soon so that will eliminate the problem.....

Though I think what's causing the issues is the o2 sensors....

After my hg change the car was misfiring really bad because I needed to change the sparkplug wires....and I mean really bad...at least 2 cylinders at a time and would stall every few feet....once I changed the wires it ran better but that's when the idleing issue began and then slowly the hesitation....

Since the unburnt fuel was getting dumped down the exhaust and prob igniting there is it possible that the o2 sensors got messed up because of that...
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Old 05-02-2013, 10:33 AM   #19
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I would try changing the oxygen sensor. Any time that the air/fuel mixture is messing up in a car it's usually to blame, most common car repair in America.
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Old 05-02-2013, 10:45 AM   #20
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The misfire could be a leaky valve cover gasket. Have you checked the plugs to see if they have oil on them?

Mike
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Old 05-03-2013, 10:14 AM   #21
Jb2.5rstst
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Quote:
Originally Posted by tauntaun View Post
I would try changing the oxygen sensor. Any time that the air/fuel mixture is messing up in a car it's usually to blame, most common car repair in America.
Which sensor should I change...I know the front one is the one that controls the a/f mixture the most...

Or should I change both....
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Old 05-03-2013, 10:16 AM   #22
Jb2.5rstst
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Quote:
Originally Posted by GrimmSpeed View Post
The misfire could be a leaky valve cover gasket. Have you checked the plugs to see if they have oil on them?

Mike
When I did my hg I replaced the vc gaskets with new grommets ...new sparkplugs and wires....and that has been around jan this year
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Old 05-18-2013, 06:36 AM   #23
Jb2.5rstst
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Update


So I replaced both o2 sensors with denso oem....and customized the exhaust where there's only one cat....

Hesitation seems to be gone but I am still having very low idle when in drive or reverse and car is very rough and vibrates hard...

What else can be the issue that's causing the low iddle? When in neutral or park car idles perfectly?
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Old 05-18-2013, 07:22 AM   #24
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Throttle control sensor perhaps?
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Old 05-18-2013, 12:42 PM   #25
Jb2.5rstst
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I was thinking of that but dreading it since I know it's quite pricey....

How would I be able to check if its faulty or not
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