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Cold Stall/rough idle

(2001 Hyundai Santa Fe)
in Akron, NY on January 11, 2011
Have had a problem with my 2001 2.7l v6 AWD santa fe choking itself when I first go to start it up. If I can manage to get it to idle, it'll smooth out and keep itself running but when i put it in gear the RPMs drop to around 650 and it feels pretty rough.

What is the average idle speed?

The last time I went to start it up, I had the Air Filter box open and seemed to get a backfire.. Not sure where that fits in, but it could be related to the Fuel/Air mixture or timing.

I've been hunting around on forums to see if I can get some solid culprits on this vehicle, but my prime suspect "doesn't exist" on this vehicle- the EGR valve. Haven't had a chance to hunt for it myself, but in a pricehunt for this part, I've found no EGR for my engine.

Other Suspects include: Fuel filter, camshaft position sensor, crankshaft position sensor, PCV, and coolant temp sensor.

Haven't done too much digging yet, because I'm not exactly sure what I'm searching for.

If it changes anything, I had let my fuel levels get low this winter, and thought maybe it was moist gas, put dry gas in and it seemed to work (but it had also warmed up by that point). Next time I started it up, problem was back. Put in Fuel Injector Cleaner, under the idea that the moisture may have effected the injectors. Again seemed to help at the time, and in the process of waiting for the cooldown, to test at dead cold.

HELP..... Not really looking forward to working on this during the Buffalo, NY winter, so the fewer hours I'm chasing ghost in the snow the better.

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Popular Answer
Its so hard to guess without being able too experience these problems first hand and being able to do basic diagnostic tests. It could be so many things. A back firing in the intake could be a lean running condition may justify looking a fuel pressure and volume. Check for ignition spark, I have seen blocked up Catalytic Converters do this or bad coolant temperature switches but all these are guess' with no testing to back them up.
Plugging in a scan tool may provide a lot of information. Is the Check Engine/ Service Engine Soon Light on? If so the computer in your car is going to have relevant information stored in its memory which will help figure out what is going on. A scan tool is needed to retrieve this information. A professional grade scan tool allows key engine sensor data to be analyzed right off the scan tool without having to do intrusive testing at each sensor.
Hyundai as a car manufacturer put a lot of free technical information and workshop manuals on line for Hyundai owners. Check out lots of great information.
on June 12, 2015
I too have had the same problem going on almost a year now and I finally found a mechanic who fixed it! It was a bad coolant sensor. Hope that helps.
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