Poor Idling For Toyota D4 3s-FSE Engine

GA from me. Vacuum leaks will cause plenty of headaches. Not sure about it ...."and now only happens very unoften"

this is very helpful thanks, i guess the EGR system was fouled during the spark plug change, all this started after the plugs were changed and to change the plugs for this engine requires removing the intake manifold first. (spark plugs are those recommended for the engine)

A partial obstruction in the fuel line?

Tracking across the inside of the distributor cap?

Worn or blasted rotor arm?

Dodgy HT leads?

When EGR gets stuck open or semi-closed for long enough to make ECU suspicious from the abnormally low fresh air intake volume and call for emergency program, i.e. stall, by then carburization of intake pipe and plugs is so high that normal operation is difficult. If now EGR is sealed, you should of course have high consumption but no stalls. Now there are more... expensive possible problems like injectors, HV etc, but my money is on the severe carburization and in that case engine needs some work. Check the plugs and intake, and see. S.M.

Anytime you alter the air fuel mix without compensating the rest of the system, you're looking for trouble....

https://www.physicsforums.com/threads/removal-of-egr-system-performance-gain-or-loss.663150/

The problem is your mechanic.

He must have been a butcher before he took up his present line of work.

you have a point....if he was good enough i wouldn't be here asking questions...he said its ok to leave the EGR sealed off. is this so?

If the EGR system being sealed off made that much difference, make sure it is really sealed off. Remove the EGR valve, and use an oversized ball of duct tape to seal off the INTAKE passage that is now exposed. The exhaust will leak, but it will not hurt anything for the short time you need to run the car.

Now start the car. Is it smoother now? Is the shake gone? If so, get a new EGR valve. The car needs to have it there for all things to work correctly.

If it is not better, plug the exhaust port exposed by the removal of the EGR valve.

The easiest and quickest way I know of to remove excess carbon from the combustion chambers is to use some water. My preference is to bring the engine up to 2500 RPM with the idle speed control. Then use the smallest vacuum line available at the throttle body, or carb. The line should be 1/4 " or smaller. Let the vacuum line draw water from a quart or liter bottle. If too much water is drawn in, the engine will start to lug down. Do not let this happen. just let a small amount of water be drawn into the hose to allow the engine speed to drop only a little. Take your time. this is quicker than any other repair you can have done. as the water is drawn from the bottle, the engine should smooth out, if carbon was the problem. Give it at least two quarts of water before deciding weather or not it worked.

There you go, a cheap easy way to try to fix your car. Bear in mind that routine maintenance that needs to be performed will not be cured with this fix. Good luck.

HI thanks for this info, the idle is smoother now the only problem am still having is when the engine reaches normal operating temperature the rpm drops too low, while the car is idling, the missfire happens very unoften (like once a week for a few seconds) and the stalling has only happened once in a month since the EGR was sealed off. By the way all this started after the spark plugs were changed which required removing the manifold but the plugs are not at fault they were confirmed to be ok.

The problem is that "...the EGR system was cut off..." and the computer "knows" that. The EPA mandates that the pollution control system takes action when it sees activity known to be illegal; i.e., anything that defeats a pollution control system.

Of course it doesn't know if it's because the EGR was removed or suffered a total failure, so it degrades the performance enough to allow the vehicle to be driven, at the same time that it makes it uncomfortable to do so.

If you want relief put in a new EGR or try cleaning up the old one, that's the only permanent fix. If you continue to drive the car any appreciable distance the high fuel consumption will cost more than the EGR will.

The car indeed does monitor the operation of the EGR system, but that system does not operate at idle speeds, so the idle smoothness should not be affected.

True, it should be closed at idle, but when the EGR is stuck and doesn't close tightly, exhaust gas will upset the desired air/fuel ratio and have a noticeable effect upon idle depending upon how wide open it is where it's stuck. Worst yet, it has sensors that affect what the ECM does to the ignition timing, fuel injection timing, catalyst operation, etc. so it can have a profound effect on overall engine performance.

I usually lift the vacuum line to it and see if it affects the idle. If it stays rough I reapply the vacuum while gently rapping the valve a few times, sometimes it's enough to free up the valve and the idle returns to normal, cycling the vacuum a few times will tell you if it's going to stick at the same place. At that point you can decide if it needs replacement or cleaning, but on some engines it's such a pain to get to that it's less labor intensive to just replace it.