Idle issue - Toyota Nation Forum : Toyota Car and Truck Forums

stanno · 03-07-2011, 06:53 PM

Hey guys;

Can anyone help me diagnose another strange issue?

The manual says to have the engine on and the transmission in park, and adjust idle at around 700-750 rpm (someone correct me if i'm wrong).

My idle speed is set at the prescribed rpm as stated by the manual. Engine idles real smooth (when in gear). However, that changes in the night time.

At night, the engine idles at a lower rpm (when in both Neutral and Drive) than it does in the day time, without me touching the adjustment screw.

The difference is so noticeable, that if i'm stopped at a traffic light (in the night), i sometimes have to shift to neutral because, when in gear, it idles so low it causes excessive vibration.

What could be the cause of this?

nopain00 · 03-07-2011, 07:15 PM

Are you letting the engine warm up to operating temperature before setting the idle? You can't set it correctly on a cold engine.

stanno · 03-07-2011, 07:19 PM

At the time i had set it, i had just came off the road doing maybe half hour of driving, so the engine was well at operating temperature.

It idles lovely during the day, it's just at night the idle goes lower, most times to low (when in gear)

typesix · 03-08-2011, 10:58 AM

Used to have a similar Camry, when headlights are on at night, the idle should increase just slightly automatically to compensate for the electric load. The rpm increase is not as high as when AC is on. The computer sees an electrical load increase and is supposed to increase the rpm.

stanno · 03-08-2011, 02:05 PM

Quote:

Originally Posted by typesix

Used to have a similar Camry, when headlights are on at night, the idle should increase just slightly automatically to compensate for the electric load. The rpm increase is not as high as when AC is on. The computer sees an electrical load increase and is supposed to increase the rpm.

I hadn't considered that the decrease in rpm at idle could be attributed to the load of the headlight & fog-lights.

I'll take note of the idle rpm range tonight with the headlights & foggies off.

holmesnmanny · 03-08-2011, 02:46 PM

What's supposed to happen is that when you put a load on the engine by turning something on(except ac)the idle will slightly increase to account for the lose of power from the extra load. Your rpm's should go slightly up, not down. What could be happening is that your idle control valve is not working correctly because the port is clogged and isn't able to raise the idle because it's too old/dirty.

What could also be happening is that you are misinterpretting the idle. When you have no load the idle should be around 700, then when you turn something on, the idle should slightly raise. Then if you turn it off, the idle should slightly raise, due to the fact that the idle control valve has previously added to the idle and now you don't have the extra load, then it should dip back down.

I would take off the intake tube and spray some carb cleaner all around the inside of the butterfly while keeping the butterfly open so that all of the gunk can leak out. A lot of times the idle control valve, which is located on the throttle body underneath, port gets clogged and it doesn't work right.

You should never adjust the adjusting screw. It should be set forever.

Mike Gerber · 03-08-2011, 04:06 PM

^ What holmesnmanny said. Try cleaning the throttle body paying particular attention to spraying the cleaner liberally down in to the port at the base of the throttle body leading to the idle air control valve. Spray down ther first and then go on to clean the rest of the throttle body while the cleaner soaks in to the idle air control valve. Here's a DIY link on doing it on the later 5SFE engine. Your 3SFE should be the similar.

How to: Cleaning Throttle Body -4 Cylinder Engines- With Pictures

Mike

stanno · 03-08-2011, 05:52 PM

I understand what holmesnmanny is describing about the idle and load relationship. Kinda similar to what happens if you're stationary with the engine idling and turn the steering and the power steering idle valve mechanism causes the rpm to increase n order to "give more power" to the pump... i think.

I've tried cleaning the TB and idle control valve located underneath with carb cleaner. I gave it - what i thought to be - a thorough cleaning too, cuz the engine wouldn't start for a couple cranks (so i figured i used alot of cleaner)...

I'm gonna give it another clean, this time, i'm gonna really try and get the cleaner inside the control valve hole.

If that doesn't correct it... i think i'm just gonna take off the TB and idle control valve from the plenum and inspecting it and clean it while off the plenum.

Thanks for the link Mike, i read that thread some time back... it's how i knew what to do when cleaning it.

holmesnmanny · 03-08-2011, 09:56 PM

Quote:

Originally Posted by stanno

I understand what holmesnmanny is describing about the idle and load relationship. Kinda similar to what happens if you're stationary with the engine idling and turn the steering and the power steering idle valve mechanism causes the rpm to increase n order to "give more power" to the pump... i think.

I've tried cleaning the TB and idle control valve located underneath with carb cleaner. I gave it - what i thought to be - a thorough cleaning too, cuz the engine wouldn't start for a couple cranks (so i figured i used alot of cleaner)...

I'm gonna give it another clean, this time, i'm gonna really try and get the cleaner inside the control valve hole.

If that doesn't correct it... i think i'm just gonna take off the TB and idle control valve from the plenum and inspecting it and clean it while off the plenum.

Thanks for the link Mike, i read that thread some time back... it's how i knew what to do when cleaning it.

If that doesn't fix it you might wanna think about just going down to the junkyard and pulling another idle control valve and swap that on.

Make sure you got the idle base speed correct 'though. There is a chance that it was originally off. You will need the car in neutral and IIA service connector coming from the distributor. Only the 2S-ELC 3S-FE AND '94 1MZ-FE AND '92-'95 5S-FE engines have adjustable idle speeds, going by what my chilton shows.

stanno · 03-10-2011, 08:24 AM

Quote:

Originally Posted by holmesnmanny

IIA service connector coming from the distributor

Could you enlighten me on this part.

holmesnmanny · 03-10-2011, 07:44 PM

Quote:

Originally Posted by stanno

Could you enlighten me on this part.

Sorry, that should read "unplug the IIA service connector coming from the distributor". I pulled that straight out of my Chilton.

nopain00 · 03-10-2011, 10:11 PM

The IIA connector is a small female wire connector attached to the distributor, with a plastic cover over it. You need to plug your tachometer into this connector to read the engine speed. I used a male spade connector that I rigged to my tach to connect to it. Make sure that the connection is good and you're not shorting it out to ground, which could ruin the coil.