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Old 06-28-2006, 11:55 AM   #1
Scooby Newbie
Member#: 82725
Join Date: Mar 2005
2001 Impreza RS

Default engine hiccup and sound from....AC?

For the past week my car has had a slight hiccup problem. Periodically i will hear a quick "chk" sound that i *think* is coming from towards the front of the car, and the car will hesitate just slightly for a split second. It is slight enough that i don't think anyone who isn't driving the car would notice, and it is very quick. But i know i am not making things up, because it happens often. I haven't been able to pin it to a specific RPM, and it seems to do it under soft and hard acceleration, and cruising, though maybe the most often under soft acceleration. The best example i can think of is that it almost feels as if the wheels hit gravel and lose traction for half a second. I don't lose control of the car or anything, but the slight hiccup in acceleration feels like that.

From yarrgh's suggestion on this forum i checked to see if it was related to my AC, and sure enough, the problem only happens when my AC is turned on. What in the world could this be then? Is it something i need to be worried about? How do i go about fixing this problem?

Any and all suggestions are appreciated.

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Old 06-28-2006, 12:02 PM   #2
Trust no one
Member#: 11170
Join Date: Oct 2001
Chapter/Region: Tri-State
Location: NYC
02 WRX
15 WRX/05 GTO


It is the compressor cycling on. When it engages you may notice a change in engine load. It shouldn't be that extreme however, if you feel it is excessive it may be prudent to get the AC checked. If it's overcharged the compressor may be loading the engine more than it should.
It would help if you complete your profile to include the model and year of your car. This may be a warranty issue but without knowing how old your car is we can't say for sure.
Mulder is offline   Reply With Quote
Old 06-28-2006, 01:12 PM   #3
Scooby Newbie
Member#: 93204
Join Date: Aug 2005
Chapter/Region: PRSIC
Location: Caguas, Puerto Rico
2005 Impreza
San Remo Red


My car is a 05 2.5rs and it does have the same symptoms. I put a tread like this one on the N/A forum but I did not get a good answer. My does it with and without the A/c.
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Old 04-18-2011, 06:41 PM   #4
Scooby Newbie
Member#: 174772
Join Date: Mar 2008
Chapter/Region: NWIC
Location: Vancouver, WA
2004 Impreza 2.5rs

Default 2004 2.5rs

I have the same exact issue happening with my Subaru. Someone told me it may be a vacuum leak but I can not seem to figure out what the hell is going on with it. Its been going on for awhile now but hasnt gotten any better or worse. I hear the chirp in the intake when it hesitates for that split second around 2500rpm.
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