weegie01

Hello,

I hope someone have seen this issue before and could help with a workaround.

Issue:

When I start the car it start fine but when I turn on the AC and start driving if I come to a stop where the car is idle it will idle really low and the car dies. If I turn off the AC and the car is idle the idle seems to be normal and everything is okay. Have anyone seen/heard of this issue before? My S2K is an 06 with about 84K miles.

Thanks for any assistance that you can provide.

Weegie

Nand01

Adjust your throttle body cable, when the AC turns on it requires a little more power from engine/ pulleys, so basically adjust it so it idles 2-3 notches higher at the cluster. over time the cable stretches hence needing adjustment.

iviaillet

I don't think a loose throttle cable would affect the idle, but it would effect the engine receiving %100 throttle. There is a throttle stop screw which noted by the factory Honda service manual you should not adjust.

Is the engine all original? Or has it had major work done recently?

If it were my car I would check the air filter first if that were good I would clean the IACV, then I would check the spark plugs, fuel pressure, ignition timing (it's good to know all this is good condition) if that's all good I would check the Idle speed. Here's a page that pretty much sums it up, directly from the Honda service manual...

NOTE:
A. Leave the IAC valve connected.
B. Before checking the idle speed, check these items:
- The MIL has not been reported on
- lgnition timing
- Spark plugs
- Air cleaner
- PCV system
C. On Canadian models, pull the parking brake lever up. Start the engine, then check that the headlights are off.


1. Disconnect the EVAP canister purge valve 2P connector.

2. Connect a tachometer.

3. Start the engine. Hold the engine at 3,000 rpm with no load (in neutral) until the radiator fan comes on, then let it idle.

4. Check the idle speed with no-load conditions: headlights. blower fan, radiator fan. and air conditioner off. ldle speed should be: 800+/-50 rpm

5. ldle the engine for 1 minute with the heater fan switch on Hl and the air conditioner on, then check the idle speed. ldle speed should be: 900+/-50 rpm
NOTE: lf the idle speed is not within specification, see Symptom Chart.

6. Reconnect the EVAP canister purge valve 2P connector.

Adjust the idle speed.
To complete the idle learn procedure do this:
1. Make sure all electrical items (A/C, audio, rear window defogger, lights, etc.) are turned off

2. Start the engine.
Hold the engine speed at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, or the engine coolant temperature reaches 176'F (80") 212"F {100").

3. Let the engine idle for about 5 minutes with the throttle fully closed and with all electrical items off.
NOTE: lf the radiator fan comes on during this step, the time when it is operating must not be included in the 5 minutes.

weegie01

The engine is the original and no major work done. The only thing that was done in the past was adjust the valve. The only other thing that Honda recommended from my last visit is to change the motor mount but I haven't done that yet. I will try all of your suggestion and see if that will take care of the issue. Thanks so much again!

mbs

I'm having the same issue. I've documented my progress so far over here:

https://www.s2ki.com/s2000/topic/964...when-ac-is-on/

rob-2

Question, have you had the car 're-learn' idle?

Re-set ECU
Wait 15 minutes
Start car up with no accessories on - fan off, radio off, ac off etc etc
Let car idle until the engine fans come on two times

Go drive the car about 300 miles.

Report back

NOE-S2K

06+ don't have IAC or throttle cable because of the DBW(drive by wire) system. I have an 07 and have been dealing with idle issues on warm starts nothing major but hopefully someone knows how to fix this issue on 06+ cars with DBW.

xviper

You use the A/C because it's the hot season (obvious).
When it's hot out, your engine's power and torque curves shift so you get less power at every rpm, especially at low rpm. Idle means the least amount of power being produced. The engine still needs to drive itself, the flywheel, the clutch assembly, alternator, water pump, etc. Then you add in the extra parasitic draw of the A/C compressor. The engine's ECU may not have time to compensate fast enough to keep the idle rpm elevated when you push in the clutch to come to a stop. Some things you can do:
As already indicated, make sure things like sparkplugs, air filter, IAC, MAP, TB, fuel, cat are all good and/or clean. This allows the engine to perform as best it can under these conditions. Adjusting the slack on the cable (for the cars that have them) does nothing for the idle and may only confuse the ECU. The throttle cable on an electronically fuel injected engine is NOT for regulating idle. Idle is done by the ECU using solenoids and the IAC system. The throttle plate should NEVER be pulled by the cable to set idle. This is bad advice.
Next thing you can do for yourself and the car ............................ It is particular important and helpful to NOT push the clutch too soon when coming to a stop during hot ambient temps. Don't coast too long to a stop. Downshift to second (first if you can do it smoothly), leave the clutch full UP for as long as you possibly can (at least till the rpm reaches 1000 or just below). This forces the ECU to fight the dropping rpm and keep it higher. Once it gets to just below 1000 rpm, THEN push the clutch in. Do this consistently and your dropping idle and dying motor may be a thing of the past. If you do it too much above 1000 rpm (even 1500 to 2000 is not good enough), it will not help.

This is a very high strung engine (even higher than other "performance" engines) and idling is not one of the things it does well and Honda has done a remarkable job at making it work as well as it does. I won't go into things like cam profiles, timing, etc because unless you come from a time when everyone talked about 1/2 race, 3/4 race and full race cams, lift and duration, high advance, you won't understand anyway. These things conspire to make an engine not want to idle at all.

iviaillet

Don't quote me on this but I think the VSS's input affects idle, seems like on a lot of manual transmission cars the idle comes down a bit when you come to complete stop while in neutral the whole time.