Hachiroku $B%O%A%m%/ wrote:
> On Sun, 11 Mar 2007 21:00:58 -0500, the phelper wrote:
>
>> 1999 Civic EX 5spd
>> 140k miles
>>
>> At idle, such as at a red light, *sometimes*, maybe 1/3 of the time to 1/2
>> of the time, the tach will show the RPMS going up a few hundred, then back
>> down several hundred more. Up and down, up and down... Only when the AC
>> is on. Sometimes the RPMs have dropped significatly, and the engine seems
>> to shake as if starved for gas or air or whatever.
>>
>> Vaccuum leak in the AC system?
>>
>> PS... not that it matters, but the AC control unit is on the frizt... this
>> is the dealie next to the stereo, with the 3 knobs that control a) Which
>> Vent, B) Temperature, C) Fan Speed. During the fall, I started having
>> trouble with it, then in the winter all the fan speed knob stopped
>> working. Temps have warmed up with Spring at hand, it works better now.
>> I'll think about replacing it during the fall unless it dies in the
>> summer. Mentioning this...just in case....
>
>
> Off the top of my head, two things came to mind:
> You have a vacuum problem, like you mentioned.
> Your Air Flow sensor needs cleaning.

honda don't have an air flow sensor. they have two air pressure sensors
and they measure the differential between them. no cleaning required.

>
> Look for vacuum leaks or a stoppage, and you can try to cleanthe AF sensor
> with carb cleaner or Lectro-motive (keep away from rubber or plastic).
>
> But, since you mention the AC problem, try turning the HVAC system OFF
> totally and see if it goes away. If the compressor is off, then when the
> system turns on, it may be loading the system too much and causing your
> problem.
>
> As far as the fan control, these are controlled by a resistor pack,
> usually located in the fan or behind the control; it looks like three or
> four little springs. Does it work on some speeds but not others?
>