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Discussion Starter #1
Hey guys, the car tends to only get rough idling when car is already warmed up and with the AC cycling off and lowering the rpm into the 500s. It would bring up to the 600s but its hella annoying when AC is cycling on and off frequently at the light and feel like my car is gonna break itself.

I did some search relating to rough idle and found some basic problems like plug gap and IAC, but nothing related to my symptom. My plugs look to be in normal wear and tear and gapped to .032" and checked recently. When in neutral and all accessories off, it idles in the 650s. Start up and warm up, drivability all doing well. Only other thing I noticed more recently is cold engine and slow driving, the trans seems to be hunting for the right gear, but doesn't have a problem when warm... may also be related to AC.

Any pointers or directions I can look into would be great
 

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This can have a lot to do with engine management if you are no longer stock. There is correction that needs to be programmed in for running the AC. Are you saying the idle decreases AFTER the AC kicks off? Is the idle your issue or the AC switching in and off? If it's just the AC you probably have a leak and need a charge. In otherwise healthy systems, compressor seals will be most common at the age of our cars.

Get us some more details on what you have and clarify on what it's doing and the collective 'we' can offer better assistance.
 

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Discussion Starter #3
I am on stock ecu, the AC kicks in and rpm blips up to 800s. Then the AC disengages and the rpm drops to 500s and the car shakes until it normalizes back to 600s. I assume the AC is workin fine but I may be wrong. I will try to get more data on when AC is completely off.
 

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I am on stock ecu, the AC kicks in and rpm blips up to 800s. Then the AC disengages and the rpm drops to 500s and the car shakes until it normalizes back to 600s. I assume the AC is workin fine but I may be wrong. I will try to get more data on when AC is completely off.
In that case you have too much correction. IACV is a definite possibility here. Also check out the dashpot, throttle opener and TPS on your throttle body. Mine has a cut in the vacuum line for the throttle opener and it caused all kinds of strange idle behavior.
 

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I have the same problem you describe, OP. Symptoms are basically identical. I don't drive the car enough for the A/C to get much usage. I'm not sure if my RPM drops when the compressor kicks on or off, I figured it was when the compressor kicks on. I'll have to look into it some more.

I'm on a stock Aristo ECU. No refrigerant leaks, system is charged correctly.

I'll look into what carman336 suggested.
 

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Discussion Starter #6
So when I don't have my ac on, the car idles perfectly at 590 rpm, when the ac on and compressor cycling, it can drop all the way to 530! So looks to me like you were right that it over corrects. Is there a way to adjust this or what do I need to replace?
 

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Start by confirming your throttly body is set up correctly following the tsrm. If it's off the car may not know how to correct the airflow when ac is on. Alternately the iacv may need replacement but I recommend confirming your throttle setup is correct first as that procedure doesn't cost you anything but time.

While you're in there it's also a good idea to make sure you don't have excessive carbon buildup in the throttle body and intake assembly. That can also cause idle issues.

Lastly if your compressor is on its way out the extra load could be creating a larger load than the ecu is programmed to correct and you will need to replace your compressor.

Is the compressor noisy or quiet? You really shouldn't be able to hear much from the compressor. If it squeaks or hums you probably have bad bearings.
 
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