PolarisJack

Hey all, I have a 95 pickup with a sticky throttle and surging idle. A mechanic cleaned the throttle body and put a new IAC on, and that didn't help. He suggested I buy a new throttle body, which I was about to do but when I got looking at the work he did, I noticed he'd bypassed the new IAC with the coolant lines. I have no idea why he did that (he retired right after working on my truck and I can't reach him). I rerouted them back onto the IAC, but that didn't affect the running of the truck at all.

Any thoughts?

The sticky throttle settles back down if I rev it up a few times. The spring seems to be working fine, but I'm not positive. And the throttle body did look clean when I pulled the intake off...

If I need a new throttle body, is a used one a good idea, or from LC Engineering?

Many thanks!

Jimkola

Is it sticky even after it warms up?

PolarisJack

Yep, stays sticky. And the rpms jump from 1,500 to 2,000 and back.

snippits

Burp the coolant system. The 22RE engines can and will idle surge when there is air in the coolant system. I reckon it has to do with air pockets inside the IAC.

Jimkola

Might also check the shaft the throttle plate attaches to. If there’s noticeable lateral movement/play the bushings may be worn. I know you can get new seals for the shaft, but I haven’t found bushings yet. At least not ones identified as such.

PolarisJack

Okay, sounds good! Thanks.

I did top-off the coolant after doing the lines, and I burped it a bit but not very thoroughly. I'll try again. That could account for the idle surging, but not the sticky throttle, correct?

How do I check the shaft on the throttle body? Just by trying to move it from the outside? I'll mess with it.

Thanks again!

coryc85

When you say sticky throttle, you just mean that the RPMs are high when you let off gas, you blip the pedal and they drop to normal idle range, or do you mean actually that your throttle plate in the throttle body is literally stuck at a certain position sometimes?

If it your throttle plate moves freely, but you don't feel that RPMs always drop like they should, you can pull your TPS off and make sure that if you move the ears on it, the spring always snaps it back to the idle position. When you press the gas pedal the pawl on the throttle body moves the TPS ears along with the throttle plate, but the only thing that moves the TPS back to the idle position is the little spring on the back of the TPS, and I know mine was crusty and the TPS did not always snap back to idle position. So your throttle plate can close when you let off the gas, but the TPS itself may not always snap back to idle, blipping the throttle will free it up to snap back.

I don't know that would cause surging idle though, but it's a free check you can do. Also, you may want to pull out your idle set screw and change the o-ring if you have never done it. Put on a new one, and that should help keep your idle screw where you set it and will eliminate that as a potential vac leak.

PolarisJack

Good call. Yes, by "sticky" I mean that the RPM's don't drop back down when shifting or stopped. And yep, when I blip the throttle it does drop. I'll try to check the TPS. New territory for me.

I wonder if the mechanic who bypassed the IAC changed the idle screw adjustment, too. The truck doesn't fire right up like it did before he messed worked on it. Kind of a weak start.

Thanks a ton!

snippits

Sounds like the dash pot could be sticking. I took mine off on my 92 because it was sticking. It's mounted on the side of the throttle body, and keeps the throttle from slamming.

https://www.yotashop.com/dash-pot-to...oaAhKEEALw_wcB

PolarisJack

Good call. I wondered what that thing was/did. When I operate the throttle manually (with my fingers) I can see it throttle back to a point, hang there, then eventually drop back to a normal idle.

I'm in the middle of a move now, so won't have time until Sunday or so to mess with this stuff. Thanks a ton for all the thoughts! Super cool.

Also, I do have a parts truck out in the woods with a throttle body on it. It's a high miles truck that's been sitting for 15 years close to the coast of Maine... it doesn't look pretty, so I'm guessing it's probably not worth pulling and trying. An engine fire toasted most of the wiring, so the sensors are probably shot. But I'll see if I can compare the movement in mine with that one.

Thanks again.

bucketyota

This isn’t really related but I had a question my truck suddenly started to misfire and got a surging idle I changed the fuel rail, injectors, fuel dampener, and fuel pressure regulator and no change I also changed the TPs it gets horrible gas mas mileage with a strong smell of gas spark plug’s are wet with fuel spark plugs are for the most part new and I have wires from lce and a new distributor cap. Goes up to 2k rpm’s then drops to about 500rpms and sometimes stays at 1k rpm’s im completely stumped I had some codes about the afm and TPS any advice would be helpful.

PolarisJack

Just an update about the throttle body stuff for those who offered advice. Between work and rain (every day...) I haven't had much time to mess with it, but I did burp the antifreeze and top it off again, and that seems to have solved the idle surging problem. The throttle still sticks, but I haven' t had time to work on any of that yet.

Thanks again for the input!

2ToyGuy

Fuel DAMPER, not DAMPENER.

A dampener would be a device that gets the fuel wet. Like with water. A damper is a device that reduces/eliminates surges in fuel pressure. Whatever the cause might be.

Sorry, just a pet peeve of mine.
Pat☺

PolarisJack

Another update. I removed the adjustment screw for the dashpot, and that seems to have mostly fixed the sticking throttle--but not all of the time, and not completely, which seems odd to me. I suppose the next step would be to swap out the TPS? The truck still idles pretty low at start-up.

As for the surging idle, I've discovered a slow leak in the antifreeze--water pump, I believe--so the surging comes back as soon as the antifreeze gets a little low. Looks like I'm in for some more work.

Thanks for all the thoughts!

Jimkola

I replaced that short spring with a new one to help the throttle cable return. that helped mine return to idle speed faster