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What would cause erratic idle when the egine is cold??

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Old Nov 18, 2003, 09:24 PM
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Unhappy What would cause erratic idle when the engine is cold??

Recently my car hasn't been able to idle when the engine is cold, the dealer has checked the car and even replaced 2 02 sensors and it still does it. Has anyone had this problem before??
Old Nov 19, 2003, 05:44 AM
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A high idle when cold is normal due to emissions compliance now necessary with this car. It just may be more pronounced now that it's gotten a bit colder out. Does the idle settle down to 850RPM after about 10 minutes? If so, that's normal.

I park my Evo outside (blasphemy, I know) and it idles at 1900RPM when I first start it up, but settles down to 850RPM after about 10 minutes. This is done by the ECU in order to properly warm up the catalyst to comply with silly startup emissions. Blame California.
Old Nov 19, 2003, 06:35 AM
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I've noticed, now that the weather has cooled down (Detroit), I find the engine 'stumbles' or 'bogs' when I shift from 1-2 and 2-3. Only for the first couple of minutes until it warms up. Have you found this too?
Old Nov 19, 2003, 06:54 AM
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yeah i dont have an evo but the same is true for my lancer and my bro's eclipse. Flip is sayin that his car is stalling out--have you got a computer flash or chip installed? Or even a CAI? I know with my dad's lightning we installed a CAI on it and now that winter is rolling around it is having some problems ideling (he has a chip installed too and many other mods)
Old Nov 19, 2003, 07:11 AM
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i love how dealers are so quick to blame O2's
Old Nov 19, 2003, 10:37 AM
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I don't have an Evo, but my STi would have a rough idle with the eingine going up and down by a few hundred RPM's. I put in a grounding kit and it is very smooth now.
Old Nov 19, 2003, 12:51 PM
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First thing is do you have any mods at all?
Any type of vacuum leak from a boost gauge or a crappy BOV can cause the idle problem. The recirc valve (like stock won't).

Next thing is how long has it been going on for? ****ty gas is a possibility if it hasn't been long. I am assuming if they replaced O2 sensors the car was checked for the recall, which will also cause it.
Old Nov 19, 2003, 03:04 PM
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my mods right now are a 3" turbo back with a high flow cat, after the turboback install the car ran fine. Then a week or so later an exede unit was installed and i think something happend during the install because it only started after that. So we took out the xede completely and the idle is still off, so i'm thinking a boost leak or a bad maf. any ideas???
Old Nov 19, 2003, 03:14 PM
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Originally posted by sparkin3
I've noticed, now that the weather has cooled down (Detroit), I find the engine 'stumbles' or 'bogs' when I shift from 1-2 and 2-3. Only for the first couple of minutes until it warms up. Have you found this too?
I sure as hell have this.... Was a little worried cuz I thought it was just me... The car bogs really bad sometimes if I haven't let my car warm up for like 2 minutes..
Old Nov 19, 2003, 03:30 PM
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Originally posted by tpm17


I sure as hell have this.... Was a little worried cuz I thought it was just me... The car bogs really bad sometimes if I haven't let my car warm up for like 2 minutes..
Same here!!! It never happened when I first bought it since the weather was very warm so it didn't take a lot to warm up the engine. But the cooler it got the more and worst it got. But after it got warmed up a bit, it is perfectly fine. So I figure it just need a little bit of warm up. I was a bit worried that I was the only one getting this too.
Old Nov 19, 2003, 05:56 PM
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Originally posted by b18flip
my mods right now are a 3" turbo back with a high flow cat, after the turboback install the car ran fine. Then a week or so later an exede unit was installed and i think something happend during the install because it only started after that. So we took out the xede completely and the idle is still off, so i'm thinking a boost leak or a bad maf. any ideas???
Did you reset the ECU after removing the Xede?

I would double check the Air box installation, I am assuming you removed it when you took the boost restrictor pill out.
Obviously the dealer should have done a visual on the car when you went in with the problem.
Did you put the boost restrictor back in when you removed the Xede? I am just wondering if it was apart and put back together after it was already having the problem.
Old Nov 19, 2003, 06:12 PM
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Originally posted by 4G63>OOOO
A high idle when cold is normal due to emissions compliance now necessary with this car. It just may be more pronounced now that it's gotten a bit colder out. Does the idle settle down to 850RPM after about 10 minutes? If so, that's normal.

I park my Evo outside (blasphemy, I know) and it idles at 1900RPM when I first start it up, but settles down to 850RPM after about 10 minutes. This is done by the ECU in order to properly warm up the catalyst to comply with silly startup emissions. Blame California.


Wow, 1900 is pretty high... mine idles at about 1200-1400 for about 3-4 minutes and drops back down to 850.... I live in Vegas so we have about the same weather conditions, I wonder which is normal....
Old Nov 19, 2003, 06:13 PM
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Its cold here today (snowed) At start up after work its about 1450, then gradually goes down to 900 after about 7mins. (I wait and time it) Anyway at a few lights rpm dropped to 700 or so, but then jumped right back up to 850ish. Heater is on and rear defroster too, and windsheild wipers. May be partly the battery causing this too.

I hit fuel cut again in 2nd gear in upper rpm range. It only happens when its this cold out due to the dense cold air, has anyone with out a piggy back or other computer upgrade hit fuel cut with a stock car and ecu?
Old Nov 21, 2003, 10:09 PM
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Originally posted by timzcat


Did you reset the ECU after removing the Xede?

I would double check the Air box installation, I am assuming you removed it when you took the boost restrictor pill out.
Obviously the dealer should have done a visual on the car when you went in with the problem.
Did you put the boost restrictor back in when you removed the Xede? I am just wondering if it was apart and put back together after it was already having the problem.
yup the pill was put back in BUT the ecu wasn't reset. How do you do it?? (sorry for the noob question)
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