Rpm Drops While The Ac Is On...

[sunny747]

my car has 4g63na engine with 2.0 cc. Recently it had an annoying whining noise and garage guy changed some Belt and it was okie. But after that, i feel the RPM drops when i turn on the AC. sometimes i feel like the engine will stop.

Usually, RPM remains on 1000 but drops to 500 when AC on. Sometimes it fluctuates to 200 while shifting gear and car shakes for few seconds then again RPM goes up to 500. My my ac works fine and it is very cool.

I feel the engine has not been tuned well or the ECU is not compensating the energy loss while the AC is on.

what do you guys think?

The garage that i go, i have seen them tuning the engine with some screw driver manually but never used any computer to access the ECU.

does Mitsubishi service center has any service for tuning only?

thanks.

[transam]

Think all motors now have an automatic air valve ( can't think of the proper name ) which adjusts the air flow at idle to keep idle speed constant whenever load is applied. Could be bunged up, or wiring connection, worth checking.

[garyh]

Could be a vacuum leak somewhere if the mechanic forgot to put one back on or accidentally broke a hose. Lift the bonnet and listen for air sucking when the AC is on.

[sunny747]

Hi garyh and transam...thanks for your reply...appreciate it..

well, there is no noise of air sucking...things look very smooth...

i have also noticed, RPM improves (while AC on) when the engine is hot.

In the morning especially, i just can't hit the ac button. I need to drive few minutes before rev goes high.

still not sure about the problem....

[garyh]

The ECU operates on different settings when the engine is cold. Sounds like you need to find someone with the right gear to analyze it.

I bought a adapter on Ebay for a Nissan I had so I could connect a laptop to the ECU and see what was going on with it.

[WarpSpeed]

Throttle control sensor, if it happened after the belt was changed maybe they disconnected something and didn't hook it back cup..

[transam]

Hi garyh and transam...thanks for your reply...appreciate it..

well, there is no noise of air sucking...things look very smooth...

i have also noticed, RPM improves (while AC on) when the engine is hot.

In the morning especially, i just can't hit the ac button. I need to drive few minutes before rev goes high.

still not sure about the problem....

Look at the air intake tube after the filter. Not sure your configuration but there is usually a small pipe plumbed into the main pipe with a valve Tee'd into it. Has an electrical connection on it. Make sure it's connected or disconnect and reconnect, in case just a bit of corrosion on the electrical pins.

[Semper]

sunny, go back to the garage who changed the belt and don't leave until you are happy with your motor.