Just finished up head gasket job on ‘94 4Runner with the 3.0. It was quite an undertaking, but i feel like I got everything correct. Truck runs great. The only slight issue I had was it seemed to be idling high. 1500 rpm at idle. I checked ignition timing and found it very advanced. A good bit past 15 degrees advanced…I would guess 20 degrees. I know factory spec is 10 degrees advanced with the terminals jumped out, so that’s where I set it. The truck ran like CRAP! It would start and idle fine at about 900 rpm. Driving it, however, was another issue. Extremely sluggish and acted like it didn’t want to take any gas. So much so that I was scared to drive it. I set timing back to around 18 degrees advanced and truck runs much better, but idle is high. Around 1200. My question is, why does it run so poorly at the recommended timing? And, should I even care?

 

So, after driving the truck a little more, it isn’t running as good as I was thinking. Timing set at 18 degrees advanced. Just very sluggish. 5 speed manual. The best way I can describe it is like this…..if the shift range for each gear was 1000-3500 RPMs, the truck is sluggish from 1000-1500, and again from 2500-3500. Seems to accelerate Ok in the middle of the range. If that makes any sense at all. Any guidance would be greatly appreciated.

 

First thing is are you sure the harmonic balancer hasn’t slipped a few degrees? Second thing is to set the idle speed to 750-800 rpm before you adjust the timing. There is an advance curve with rpm so unless the speed is right the number doesn’t mean much. The big brass flat head screw facing you on the side of the throttle body adjusts the idle speed. My truck runs best at 15 degrees at 800 rpm.

 

Actually, the BIG bras standard screw, is a cover for the actual idle adjuster screw. You may be allowing more or less air to flow into the area of the actual idle adjust screw by adjusting the cover screw. If the o-ring on the IAS is failed, that might well adjust your idle.
You might want to take the cover screw off, and pull the IAS to check it's o-ring. They're a known failure item and very available, and easy to change out. Let's face it, rubber only lasts so long. Make sure you screw the IAS down till it stops, counting the turns, including fractions there-of, so that you know where it was the last time it was working right. It's a good starting point, anyway.
As I said, the o-ring has a problem with disintegrating. If it has, you'll need to clean any bits, chunks, etc out of the small little air passages the screw controls. It's just generally a good idea to give the air passages a short squirt of carb cleaner, just for GP.



Not the greatest pic in the world, but the Idle Adjust Screw COVER is circled in red. Remove that, and the actual IAS is a smaller, brass screw down inside.

 

Before you start taking things apart, confirm that you don't have a sticky linkage. Start it up, then with your finger push the throttle valve actuator (where the throttle cable attaches) closed. Nothing should happen. If you can move the throttle plate (and the engine slows), then something in the linkage is just holding the throttle open.

 

Didn't know that. I will have to take a look at mine.