Hi, as alway, thank you ahead of time for your input and help.

I have a 2006 accord 4cyl, auto with 285,xxx miles.
Just recently the RPMs have been fluctuating. When the car is in park or neutral the RPMs are a consistent 800. When I put the car in drive or the AC is turned on the RPMs drop to 650. My first guess on something like this would be the IAC valve, but I don't think this year/engine has one.

I have done a tune up on the car, pulled the throttle body off and cleaned it. Not sure where to go from here.

Thanks for the input.

Mark

 

I'd scan for engine codes next. Post the actual code on here, like P1234.

 

A little drop is normal. And if you just did work on your car, the computer may need a little while to relearn the idle.

Your car does have an IACV but thats not a common issue. Carbon build up can clog the valve a bit. You can always take it off and clean it.

However... engine load causes rpms to drop. Alternator output maybe. Do the lights dim significantly when you turn the ac on?

 

A 2006 Accord does not have an IAC valve.

 

I did the work about 4 weeks ago so I would assume that would be long enough to "relearn" There are not any stored codes nor is the check engine light on.
I can check alternator output and will post results, but the problem happens at an idle with or without the additional load of accessories.

 

I checked the alternator output.
It puts out a steady 13.99v at idle. However when the A/C is turned on the output drops to 12.49v just for 2 or 3 Seconds, the goes back to 13.79-13.99v. I am not sure what this means, if anything.

 

Thats normal.

Vacuum leaks can do odd things too. Did you make sure to change the gasket or inspect the condition of the old one when you took off the throttle body?

 

A dirty throttle plate might cause intermittent performance of idle control system. You need to clean both sides of throttle plate.

Do not force the throttle plate open, but instead turn keyswitch to On and have accelerator pedal depressed w/ a stick between seat and pedal to hold pedal fully down. Easy job.

good luck

 

The throttle body was cleaned completely inside and out, including the plate. The gasket was replaced with a new one when I reassembled.

Thanks for the ideas. I will check vacuum lines etc this weekend.