A few days ago I was out running errands and came out of one store to a dead battery. (wife and kids were in the car listening to radio with windows down for about 10 minutes while I ran in to grab 1 item).

I got a jump start and drove to a nearby auto parts store and picked up a new battery.

I noticed while driving to the store that when stopping the RPMs would drop to 500 and bounce up to 700 causing the car to shudder. After changing the battery I noticed that my auto up/down drivers window stopped working, but the regular up/down worked. I did a quick search and found how to do a reset of this by holding the button down and up for a few seconds.

After the new battery, the rough idle still remains when stopping at a light. This bouncing happens at 50% of lights and is not consistent. Sometimes the engine will idle perfectly at 600 RPM

If I turn off the A/C then there is no bouncing of the RPMs.

I did take the battery terminal connectors off and used a wire brush to clean them the best I could so that fresh metal was showing and not the corrosion build up that was there before.

There currently is not a CEL and I have not seen one pop up.

Thoughts? Is the A/C compressor failing? Is this normal? I seem to remember this happening on other hot summers once in awhile, but not every other time I stop.

FYI 2006 6MT TSX

Thanks for any input.

 

I would suggest cheking yur ground wire - not the battery post ground - but the ground wire to the frame. It may be corroded also.

 

Where is this one located? I did check the ground on the motor mount on the right side of the vehicle near the PS fluid reservoir.

 

Did you ever fix this issue? I have the same issue. Please let me know.

 

you asked if I ever fixed it less than 24 hours after I posted it...

anyway, I cleaned the throttle body and ended up reseting the ecu. I got a CEL because I forgot to plug the IAT back in.

so far so good. but I'll give it a couple of days and see what happens.

 

I'm curious about your throttle body. My idle is not too rough, but it's enough to make the radiator rattle.

Was it really dirty? What did you use to clean it? And, what type of filter setup are you using?

 

I just used some thick paper towels and my finger and ran it along the outside of the TB and wiped down the edges of the butterfly valve.

It wasn't very dirty but my paper towel was black where I wiped.

I was searching for solutions and I stumble across a tread that mentioned that the TSX doesn't have an IACV, it just uses the computer to adjust the throttle position I figured I'd take a look and see what the inside of the TB looked like and give it a quick clean.

There must have been enough there to either cause the valve to stick in low RPM idle mode or enough build up to affect air flow when the valve is closed.

I have an K&N drop in filter with the part that sits behind the fender removed.

I have 93k miles on this setup

 

When you have the a/c on the clutch on the compressor engages and is now being spun by the belt which creates drag on the engine and also creates a current draw(volts). The compressor will cycle turning on and off to keep the air cool and when it turns on it will cause the rpms to dip since the engine has to turn one more thing and also supply power to it. So if your running a/c, radio, etc there will be a bigger pwer draw lowering the rpms a little but the roughness you feel is the clutch engaging and the engine having to spin the compressor. Its normal. And when your in drive the rpms drop where as if you were in neutral they would be higher. Try to leave the car in neutral with the a/c on and see if you still feel the roughness.
Let me know what you find.

 

The car is always in neutral when I'm stopped. I don't ever leave it in gear when I stop at a light.

This wasn't just a little shaking from the AC clutch. I would come to a stop and the RPMs would drop to 500 then bounce back up to 800-900 drop to 600, bounce to 800, smooth to 700. Then after about 5-10 seconds the RPMs would drop back to 500 and repeat the cycle.

Since cleaning the throttle body the engine is staying at 750-800 RPMs. and the issue has gone away.

I still feel the slight vibration when the A/C clutch engages, but the rpms don't start bouncing +/- 400 RPM. It now bounces more like +/- 20 RPM which is what has always happened.

 

I missed your FYI about the manual part. Stupid me. But glad you got it back to normal.

 

sorry didn't realize you just posted this when i commented. I have been desperately trying figure my car out for two months and still can't. I have cleaned the throttle body inside and out...just seems to get worse over time.

 

hey there...did you ever figure this out? I’m having the same issue and it won’t go away.