I have no high idle. When the truck is cold it will idle a little higher, say around 1000. But when it gets warm it wont come down. If you drive the truck around, or snap the throttle a few times it will settle down to like 600. If you let the truck get hot, then adjust idle screw to 800. The next time you start the truck and let it get hot. It wont be at 800. It will fall down to like 600 again. No codes. No vacuum leaks.

 

First thing I would do is clean the throttle body. Make sure there isn't carbon holding the throttle plate open a bit

 

Throttle plate and throttle body is spotless. It fully closes before contacting the stop screw. I have also readjusted a new TPS.

 

Carpet/floor mat interference with pedal?


My old 86 would do this... I put a additional throttle return spring on for good measure.

 

Throttle position sensor. It is probably the most common issue with these trucks with the exception of chain guides.

 

Brand new and adjusted with a fluke.

 

If not the TPS, there's most likely a vacuum leak. Somewhere, there is a hose that is either broken or loose, letting unmetered air in which cause idle to drop. I'm wondering, do you also have any check engine lights/codes?

Try this technique, works well:

 

that right there strongly indicates that it's not on the throttle stop.

on my 22re, I can sometimes push it down to the throttle stop, no snapping the throttle, and the idle will drop.

the "fix" was to release the throttle cable holddown, where it goes under that bracket, above the valve cover... probably need to lube the cable.

you could also try setting the idle with the engine hot, per the factory procedure, then cover the idle screw with rtv... that way it won't move, and it won't leak, and you'll know where to fix the issue.

 

Make sure the AC button isn't pushed in.

 

I have sprayed a whole can on every connection looking for a leak. I cant find a thing. The throttle is against the throttle stop. I have checked and triple checked the throttle plate. With the TB off I cleaned and lubed the throttle plate shaft. Everything is super smooth, and then adjusted the stop screw. I actually backed if off about one turn. Then set the TPS. Bolted the assembly back on, and sprayed it while the motor was running to ensure a good seal. I dont have A/C on the truck. I have taken the truck for a 20 minute drive, and then came home to check the timing, and set the idle while the motor was hot. Racked the throttle a few times, only having it change RPM. I can only think of the IAC being messed up.

 

When cleaning the TB it is imperative to not only clean the plate but also clean all of the passages as well. Have you checked that your VTV and dashpot assembly are all working correctly?

 

I took the straw on the can and suck it into every hole. Made sure it flushed all the way through. The TB looked new when I was done with it. I even used high pressure air to blow out the TB cleaner. The little VTV and dashpot seem to be working correctly. If you open the throttle and let go, it will slowly bring the throttle down to full rest. Can this be removed? I have read that its for emissions. I am not saying I want to kill the world. I just want to know if I can remove it to eleminate possible malfuctioning parts. Then once I get the truck going good I will reintall it.

 

Yes many guys completely remove the whole dashpot assembly as they see it as a cause for these high idle issues. You will get a less smooth driving experience from what I've heard however. I can't personally tell you what its like driving without it seeing as I just fixed mine and got it working smoothly.

 

you can remove it from the equation, by blocking off the port where it enters the tb, on the inside of the tb.

I used a long piece of that clear wide packing tape, folded back over the outside of the tb, so that it was pinched by the rubber intake hose... had to degrease the inside of the tb where the tape was going to be.

 

There is no need to remove the dashpot. It does not keep your throttle open, it is an air valve that just closes slowly but it does not cause more pressure than the springs can compress. If you remove it, your vehicle will jerk really bad every time you let off the gas. Trust me, you won't like it.

 

It can indeed keep the throttle open if it is not compressing correctly or if the fastener is not properly adjusted.

 

Off chance, but have you checked for air in the cooling system? When hot, remove the temp sensor on top of the thermostat housing. Air trapped around the sensor can cause the ECM to be eradic. The top sensor is one of many that sends a signal to the ECM that control the injectors. There is another below the intake, near the IACV that can fail as well.

 

Good call brother. Totally forgot about this. Definitely burp your radiator.

 

I have yet to burp the system. I only know of 2 coolant sensors. I thought the one on top about in the middle from front to back of the head was only to tell the sensor on the dash what to read. I thought the one next to the cold start sensor was the ECM sensor. I have yet to check them. I dont have a FSM. What should they read out in ohms and degrees? Do they go bad often? Also do they both tell the ECM how warm the engine is?

 

Don't need to go to all that trouble yet. Just burp it real good and I wouldn't be surprised if your problem is solved. Make sure to have some distilled handy to add because when you burp it its going to be low.