Hey everyone. I know this topic has been discussed before, but I'm still unclear as to what a manual tC's idle should be once it's completely warmed up. I idle around 600 rpms and that seems way too low.

At this engine speed, the car begins to shake slightly and it's quite annoying. If I turn on the A/C, defoggers, or brights, the idle goes down to 500 rpms.

Is there anything I can do to fix this problem? Replace intake, clean throttle body, new spark plugs???

Thanks guys!

 

just taking off your battery clamps and cleaning them real well with a wire brush will help. I used a dremal with a steal brush attachment.

 

hum yea... if I'm not mistaken idle should be somewhere more in the 750 range... its hard to tell the exact value on the tach, but that seems like the range.

I suggest taking Liquid's advice and cleaning electrical contacts.

 

be sure to clean the entire thing up to the wire, it will be shiny and have a better connection

 

maybe also reset the ecu and let the car recalibrate the idle. After you disconnect the negative side of the battery for 10 minutes, reconnect everything, start the car and let it idle for 10 more minutes. Then just take it easy at first. The car's ecu will recalibrate the idle for so it is where it should be. While you are doing this, it can't hurt to clean the connectors.

 

oh.. and check things like air filters... just a thought. I'm no sure how much of an effect it'd have, but it wouldn't hurt to check that. That and oil too.

 

I think you're right. But for some reason mine idle around 600 too.

 

Welp... cleaned off the battery connections, disconnected the negative side for 10 minutes, reconnected and left it idling for 10 minutes... also checked the air filter.

After it warming up, it's still at 600-650 rpms. Do you guys have any other ideas or know of a way to adjust this manually?

 

One way to discount the spark plugs is to open the car up on a highway or interstate . If acceleration is good and cruising speed is good , sounds like the ecu needs to be reset . If it is shaking at a stop , doubt it would be the battery . Usually plugs or the ecu .
Good luck

 

and here i thought the shaking was in my head, cause my passangers dont feel it.

 

I had a similar problem, however I believe mine was caused by the spark plugs I replaced the factory ones with. I have of recent reinstalled the factory plugs and the low RPM rattle has settled down a lot. The after market plugs gap was to shallow.

 

TIGHT THE SENSOR ON THE INTEAKE!!! thats was my problem 1 month ago!!

 

Try cleaning out the mass airflow sensor. I don’t remember what I used to do so but you can look it up on YouTube. I think it was silicone cleaner spray. I had the same problem
and this fixed it

 

Yeah I agree check out your MAF "Mass Airflow Sensor" and grab some MAF Cleaner, sold at most any auto parts store. You'll need a Philips Screwdriver,
Remove two mounting screws and the wiring harness connector. Pull the MAF sensor straight up out of the air duct located here:



​​​​​Be careful with the sensor, you'll see two thin wires with a amber colored teardrop on the end, this is the sensor and it's easily damaged avoid touching it.
Just take the MAF Cleaner and spray this teardrop off. I bet it's likely dirty/coated with gunk. Just a couple quick sprays and reinstall the sensor.

Hope this helps...

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Well, before just blindly blaming MAF sensor, measure intake-manifold vacuum at idle with warmed-up engine. Then measure MAF output voltage at idle and 3000rpms. Compare those numbers with standards given in manual to see if indeed MAF sensor is malfunctioning given those manifold vacuum-readings.

Very well could be vacuum-leak from cracked vacuum-lines or loose intake hose-clamps. That really throws off MAF-sensor.

 

This worked for me. I also cleaned the throttle body barrel and valve plate. MPG improved 2 to 3 miles per gallon, city/highway dependent. Walmart sells a kit with both cleaners in small spray cans for less than $5. The small can of MAF sensor cleaner has enough chemical for multiple cleanings.

If your throttle body is dirty, you might need the big can of throttle body cleaner.

 

A couple things to note before doing this. If you have an OBD II check to make sure your O2 Evap and Cat ready checks are good. Also a per my experience, when I unplugged the battery to change the alternator and battery it took 80 miles with A/C on full blast to reprogram.
The alternator requires close to 700 rpms to begin charging the battery, so anything below will just drain it. My 05 tC ran at 2-400 rpms until everything reset so I had to fully charge the battery while it was still plugged in and ride highway speeds for an hour then headed back home.

https://www.yoursciontc.com/threads/...-unplug.67910/

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The alternator stars charging immediately when the engine is started, if it didn't, you'd get the battery indicator light on the dash/gauges. When the car is idling, check the battery voltage which should be well above 13v indicating the alternator is charging the battery. In the 12v range indicates the alternator isn't charging and you light would be on. Theres a 10 minute reset, idle the car and AC full blast for that time and the ECU would have reset. No need for the excessive driving with the AC on blast.

 

The car's ecu will recalibrate the idle for so it is where it should be. While you are doing this, it can't hurt to clean the connectors.