i got a little problem, when im in traffic and the car is idling i noticed the rpm fluctuates from 500rpm to about 1000rpm and sometimes even to 1500 and back again to 500 or even less and im not even steppin on the gas pedal. but when i turn my A/C off its gone. And this happens frequently. (it sounds like the car is breathing when i step outside)
anybody know wats wrong?

 

its because your AC is ON.

AC off means theres no extra load on the motor and belts.....AC on the idle has to be constantly adjusted due to the additional load on the motor and its electrical components which causes your idle flucuation.....1,500 is kinda high BUT if it goes back down to about 800~1,000 rpm right after you come to a stop its totally normal....both my Fit and 2000 Civic do the same thing with the AC on.

 

yup normal so dont trip on it

 

u guys sure its ok!? sometimes the rpm goes so low dat i feel the cars is gonna shut down then it goes back up again. is there anyway to fix this? maybe its the alternator or something?

 

Yes, it is 100% normal...
The AC compressor is cycling on and off... when it cuts on, RPM goes up to comensate. When it cuts off, the engine can idle normally.

 

It seams your vacuum hose for idling regulator (to compensate for extra load when A/C is on) is cracked or fall off from conector - therefor hissssing sound. Minor thing but has to be fixed .

 

yeah u r right actually!
there is a hissing sound as i remember, i will look into it in the morning and have it fixed, where is this vacuum hose for idling regulator anyways? can i fix it myself or do i need to take it to the agency?
thanks mish

 

if you have a vacuum leak, the idle will be off, but wouldn't fluctuate (much)... and it would definately not go away when you turn the AC off.
You may have a vacuum leak, but that's not what causes the idel to bounce when the AC is on.

 

I have a similar problem with my SSM 1.3 idsi Jazz. Everytime i start the car after a short trip, meaning to say the engine is already at warmed-up. The RPM dips too low almost letting the engine die-out, then it goes up again to normal rpm without AC load. I'm still guessing on what the problem is. Do you think it might be the MAP sensor?

 

i think i had the same problem with my civic a few years ago, and it ended up being the alternator, cos i would sometimes leave the civic with the A/C on while parked for a really long period.
But then again i really really hope i am wrong about this one. Alternators are freakin expensive!!!!

 

Idling rgulator (vacuum type) is on trotille body (looks like "flying soucer") with hose going to intake tract. Start the enngine, A/C on, and that hissing sound will guide you to the spot.

 

My 92 Ford Escort did that, but my Fit AT Sport shows no fluctuation of the RPM with the AC on.

 

I cleaned my Idle Control Valve with carb cleaner on my old accord and it got rid of it.

If that type of idle is normal with AC on, how come mine doesn't do it?

 

Mine doesn't do it either.

 

RPM fluctuation when there's a lot of load on the charging system is normal. a 500RPM gain or loss it too much. I'd get it checked out.