Question about 2004 Toyota Corolla
Before you could proceed, confirm the following basic adjustments:
1. Check the valve tappet clearance at operating temp (80 degrees Celsius and above)
Intake = 0.25 - 0.30
Exhaust = 0.25 - 0.30)
2. Spark plug gaps = 0.9mm - 1.1mm
3. Clean the throttle body and Idle Air Control Valve.
4. Take the Ignition key out of key cylinder and remove the battery negative terminal for one minute or more and then tight it again back.
CAUTION: BY REMOVING THE BATTERY TERMINAL ALL THE PREVIOUS CODES AND FREEZE FRAME DATE WILL BE LOST.
MAKE SURE YOU HAVE THE NAVIGATION AND MAP DVD AND THE CAR IS NOT EQUIPPED WITH TRACKER SYSTEM. IF YOU ARE DOUBTFUL DO NOT REMOVE THE BATTERY TERMINAL. ONLY REMOVE THE EFI FUSE FOR ONE MINUTE OR MORE THEN FIX IT BACK.
5. Sit on the driving seat. Keep the steering wheel in the center position. Lower the drivers window with key on engine off. Put the gear in P or N. Pull the hand brake. Switch off all accessories (heater, lights audio and video system, room light). Do not depress the brake pedal.
6. Make sure that coolant level is topped up, and engine oil level is normal.
7. Start the engine and hold the throttle paddle at 3000 rpm till the radiator fan comes on. Once the fan is on release the throttle pedal and let the engine run at idle for 8 to ten minutes. Do not open any door or operate any accessory, because doing so will interrupt the relearning process.
8. The desired idle speed is 715 -735 rpm. If it is above or lower than the desired rpm, loosen the 8 mm throttle stop screw nut, loose or tight the small Allen screw, bring it at the desired rpm and lock the nut.
Posted on Feb 05, 2013
It could be your MAF Mass Air Flow Sensor a bad resistor inside the sensor can cause a rough idle(MAF measures the air going into your engine and can cause many problems.) On top of that you should also check your EGR Exhaust Gas Release/Recirculation Valve that can also cause a rough idle(EGR Releases/Recirculates Exhaust gases into certain cylinders to cool them down and bring the engine temp. down or up(with restriction of exhaust Gases) but can cause a rough idle, Possibly just need to Clean you IAC EGR and MAF and you should be all set.
Posted on Jul 20, 2009
Have them check your IAC (idle air control) or just unplug it and see if it runs better. if so then replace it.
Posted on Apr 16, 2009
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Posted on Jan 02, 2017
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following are the general instructions on the start of diagnosing any
electronically controlled engine or transmission problem.
The engine and the automatic transmission (transmission control is only for automatics, engine is still computer controlled no matter the transmission type) in this vehicle are computer controlled and in most cases when a fault occurs a fault code is stored in the memory of the computer control module. There are exceptions to this, such as the Mass Airflow Meter and fuel pressure problems. What must be done is to have all the basic testing done such as a scan of the system for fault codes as well as a check with a live data scanner tool for engine functions that are not within range of normal, a trained technician is required to know what is correct and what isn't, then based on careful diagnostics done from a factory repair manual the correct part is replaced or the wiring repaired or the computer replaced (known as the PCM or ECM,ECU), which is very rarely the problem. Other basic checks must be done as well such as mechanical problems with the engine as well as engine state of tune and mileage on the engine. The transmission can have mechanical issues as well such as no gear engagement at all or a failed pump or other pressure related problems. Also engine mechanical problems can and do cause many drive-ability related problem such as rough idle and other symptoms.
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