Hello, new to the forums. I have a 04 honda accord 4cyl auto. Last night driving home after going up a hill, i pulled into my driveway and had a very rough idle with the break on and in drive almost wanted to stall. Rpms were around 600-700, i set the E-brake and left it in drive and could periodically see the belt tensioner move and make a clicking sound, got worse if i turned on the heat. The cel light started flashing and went off a couple seconds after i put it in neutral and the idle was normal. So i put it in drive again with the rough idle and drove around the block back into my driveway and all the symptoms were gone Ive had the rough idle/shaking symptoms before after some rough city driving but never the cel light come on because of it and it always went away. On a side not earlier this month i got the code p0171 System Too Lean (Bank 1) cel only when it was really cold outside and on warmer days would not come on, i found my throttle body intake hose was cracked bad underneath, i replaced that and the air filter disconnected the battery and the light has not come on since then. Anyway these 2 symptoms are related? Thanks

 

The auto-tensioner should not be moving with the car running. The tensioner and belt may need to be replaced. It will affect the charging system.

The earlier P0171 should be unrelated.

 

Thanks for your input redbull. I was actually just watching a video posted on this site about changing the belt. Its does seem sluggish to try to start in cold weather even with a new battery and starter. Do you think this might be the cause of the rough idle almost want to stall under heavy driving conditions periodically? thanks. oh the auto-tensioner only does that when the symptoms i described above happen. car currently has 166,000 mile give or take

 

Under load, the alternator/charging system output should be higher; so, a bad tensioner and/or belt can affect the idle and other things.

 

That makes sense, i did inspect the belt for wear, looked normal but could be stretched, tension seems tight by hand. I think i will go with replacing the belt and tensioner, as you mentioned seeing i bought this car with 110k on it, i have no idea when they were replaced and i have put 56k miles on it so far in 2 years, mainly highway. Any links on here for replacing the tensioner you know being a Super Moderator? Looking at it, it seems only a couple bolts. You've been very helpfull

 

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