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In the morning or whenever I start the car cold if I start driving before it is completly warmed up I get a really bad hesitation. It only really happens when I shift. It stops as soon as I get on it and run the engine above 4000 ar so. Does anyone have a idea about this?
 

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99 2.5 RS-T
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Answer: You bought an Impreza

Seriously though, you should let the car warm up as much as possible so the ECU can map itself properly to the weather conditions (temp, humidity, pressure). The car will run in open loop while its cold so the ECU can play with the idle and fuel enrichment settings. Also, your O2 sensors are probably below they're normal operating temp range. As long as the hesitation goes away then my advice is be patient and let the car warm up.
 

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Hi, I'm new here. But it sounds like you have a problem. The minute the car starts up, it knows all the info it needs, Ait temp, BARO, ect... and also when its warm it also controls idle speed and air/fuel ratio. What year is your car, and do you have any Mods on it. They might screw with some of the computer settings. You might want to have someone check it out. Your coolant sensor might be slightly out of spec, but comes in when it gets warm.
 

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2000 Blue Ridge Pearl Subaru I
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Actually Boy is correct. The computer does not know what's going on outside until you turn the key and start it up. Let it sit for a minute before heading out and it should be OK. Hondahater lives in CT, it gets cold there. I live in northern OH, Boy used to live there, we know about cold mornings. I don't think it gets very cold in Santa Barbara :D So don't worry about the hesitation, hondahater.....it goes away. If it gets to the point where it doesn't go away after a minute or two, take it to the dealer and they will check the o2 sensors and make sure they are reporting to the ecu correctly.
 

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Hmm lets see here. Car hesitates when cold only. Ok so the car is in OPEN loop when this happens. This meens that the ECU is not lookin at the O2 sensors. The main sensors in OPEN loop are Cooolant temp sensor, MAF or MAP sensor, and TPS sensor. And also the O2 sensors in the Impreza's are heated, so they should be hot in a matter of a minute or two. But hey, I guess that being a mechanic doesn't mean anything. I still don't know what kind of car he has, so I can't get real precise for him. But hey, if you guys want to flame me its cool.:happynow:
 

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Hmmm, what causes the car to switch to closed loop? Warming up? Hmmm, if the HEATED O2 sensors are not working properly then they will not be at standard operating temp and the car will stay in open loop... hmmm, so the moral of the story (for the mechanically inclined) is let the car warm up. O2 sensors are a very common cause for hesitation, poor running, and general headaches with the Imprezas. Speaking from experience (though I'm not a mechanic), it takes be between 3-10 minutes (depending on weather) to attain a stable idle below 1000 RPM (but the ECU has nothing to do with it, I'm sure). All it takes is patience.


edit: Its early on a Monday and I slept like crap.
 

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Hey, you stole my name! Anyways, yeah, the car needs to warm up before everything is working right. When I start my car up on cold mornings, I let it just idle for a little bit, then I keep the RPM's below 3k until the temp sensor is in the operating range. You have to let the oil circulate, O2 sensors heat up, and engine parts heat expand to the correct specs.
 

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Well, it takes more than just a warm O2 sensor to get into closed loop. I am not going to give a auto lesson about OBDII right now, so all I am saying is that the car should run pretty well in OPEN and Closed loop if all the sensors and mechanical items are in good order. The one thing we haven't talked about are those Coil Packs, if they are not putting out full voltage it will cause a hesitation. And guess what the ECU doesn't know a damb thing about how much power is at the plugs. So the moral of the story is. If you don't know what you are doing with your car, then take it to a proffessional! All the people in the world can talk online with you about it. But guess what NO car can be fixed over the internet.
 

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I've to stick with Suby81. I live up in Toronto. and it gets real cold sometimes. However I never have to idle for a minute let alone minutes before driving. I jsut start the car, put on my seatbelt and away I go keeping the rpm below 4k. No problem whatsoever. Get your car checked out.
 

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I have a 1999 2.5RS auto and it also does this. If I let it warm up for about a minute it won't do it. I can also put it in drive and hold it there for about 30secs and it won't do it. But if I start it up and go immediately it will do it. It has always done it and I have 86,000+ miles on it.

It's a temperamental beast.
 
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