jap305

Ok so i normally drive with the windows down so i can hear my b16 . But its Florida and its hot as hell so im gunna start turning on my a/c but everytime i put on my a/c and im driving the rpms drop like 2x faster then when the a/c is off. idk what is causing this and i would really like to get this fixed so i can use my a/c and drive smooth. any help is super appreciated!!!!

Former User

Any idle or A/C problems?

jap305

just some further info its a b16a2, with just a CAI and a cat back.

and i just replaces the ecu so it idles fine and the a/c is fully charged and no leaks i can see.

Former User

Does the A/C work fine?

jap305

yeah it blows cold and no leaks that i can see. just does the drop in the rpms

Robin6

have you cleaned your IACV lately?

Honda IACV explained
This thread will deluge you with more info than you've ever wanted to know about the IACV in your Honda. This information was copied out of the Honda OBD training manual as I didn't feel like paraphrasing it all.

23.1 General Overview

Idle control, along with fuel control are two of the most important sub-systems of the PGMFI fuel injection system. These two systems have a large impact on the driveability of a car. If the idle control system is not operating correctly, many driveability symptoms can occur, some of which are:

Idle RPM too high
Idle fluctuating wildly
Idle RPM too low and/or erratic
Idle fluctuating when loads occur to the engine
Fast idle too low for cold starts


The main output device that controls engine idle is the idle air control (IAC) valve. This valve was added to all models in 1988 and is controlled by at least the following inputs:

Air Conditioning Switch
Brake Light Switch
Clutch Switch (Manual Transmissions)
Electric Load Detector (ELD)
Engine Coolant Temp (ECT) Sensor
Engine RPM
Gear Position Switch (Automatics)
Power Steering Pressure (PSP) Switch
Starter Signal Input


The Honda PGMFI system is a speed/density type fuel injection system. It does not measure actual mass airflow, but calculates it from the engine RPM and the manifold absolute pressure (MAP) sensor input. On speed/density fuel injection systems, idle is controlled by simply controlling the air that bypasses the throttle plate.

The idle control system is one of the PGMFI sub systems that has seen a lot of change since the first 1985 models. The early idle control systems were primitive by today's standards. The curb idle was set by an air by-pass screw in the throttle body. This screw controlled how much air bypassed the throttle blade. Except for the fast idle controls the only other feature was a vacuum diaphragm that opened the throttle to offset the air conditioning compressor load.

The idle control systems of these earlier models had the characteristics of a carburetor. The engine control module (ECM) had no control over the idle other than the air conditioning vacuum diaphragm. To help make the idle more stable, the ECM would typically widen the injector pulse width (PW) slightly, and increase timing, when any type of load was sensed.

jbpnoman

It's called parasitic loss. With your A/C on, your compressor is spinning off the crank, stealing power from the motor and massively increasing rotating mass. What you're feeling is fairly normal.

jap305

something tells me its either a vaccuum leak, or some sort of valve that compensates for the power load thats not actuating. i really dont know but i wanna get this thing done

Former User

Makes no sense

One of the ECU's job is to try to compensate for the increased engine load caused by having the A/C on. However, don't forget that our "economy" cars will still experience performance loss when the A/C is on. What you describe seems to be normal.

grumblemarc

iTrader: (4)

No issues reported here. Sounds like normal operation.