3VZE acting strange - Time for a new throttle body?
 

I’ve only had my 93 4Runner a little over a month now, and it’s had a high idle since I got it. The idle screw is adjusted all the way in, and the best it idles at is 900rpm on average. Sometimes lower, often higher. I had a surging idle under braking, which I resolved by wiggling the vacuum hoses on the brake booster. Then today, on my drive into work, the throttle was sticking. I’d take my foot off the gas and it continued to accelerate for a few seconds before it started dropping. I’d go to shift and the RPMs would skyrocket instead of dropping when I took my foot off the gas. It got better as I drove, til it was finally back to normal on the last couple turns. Didn’t do it again when I left to get lunch.

So, right now, it seems okay, at least no worse than it has been. But this is now the third separate issue I’ve had related to idling, and I’m wondering if it’s worth just springing for a new throttle body to try and get ahead of any more potential issues. I mean, my truck only has 159k miles, but it’s nearly 30 years old and it wasn’t maintained very well before I got it. So I’m debating just replacing it, but I’m not finding any new replacements, just used ones on EBay and such. Do you rebuild these things rather than replace? And if so, is there a kit for it?

Thanks everyone!

Yeah sure. The Parts Cannon hasn't worked up until now, so you're due!

Fer cryin' out loud. You take your foot off the gas pedal, and the throttle seems like it doesn't immediately drop to idle. Did it ever occur to you that it's not dropping back to idle? Put your assistant in the driver's seat. You're looking at the throttle cable connection to the throttle body. When your assistant takes their foot off the gas, does the throttle close all the way? If you put your finger on the throttle arm, does gentle pressure close the throttle back to idle?

You could have a sticky/bad throttle cable. You could have a sticky dash pot or throttle opener. You could even have a frayed cruise control actuator or transmission throttle cable. You can see all of these right at the throttle body, and see what to fix. Or, you could buy parts on spec; you might somehow fix the problem before you went bankrupt.

Your choice.

PS Spec idle is about 850 rpm. 900 sounds pretty close to me.

Don’t gotta be a dick. Was on lunch so I didn’t flesh out the post as much as I intended, so that’s my bad. But yea, I assumed a cable was sticking or something, so I checked it out. By the time I’d got to work, it quit hanging on the throttle, so I couldn’t examine it while the problem was occurring. I checked the cables going into the TB and everything moved freely, when I pressed the rocker arm it revved up, and then dropped when I let go, as expected. All the vacuum lines are connected and I didn’t find any leaks. If it does it again, I plan on pulling over so I can see what’s causing it.

But the main point of my post is that this is the third idle related issue I’ve had in a month, so I’m wondering if I should continue chasing down issues as they crop up; or if it’s worthwhile to try and get ahead of these and any future issues by replacing or rebuilding the thing. I should probably mention, this is my first Toyota; and I’m coming from Subarus, where pulling your engine is just routine maintenance. So I’ve still got that mindset of stripping things all the way down and pouring parts into it, which I’m learning isn’t a thing you have to do with Toyotas lol

There is lots of things I'd do before replacing the throttle body, that can cause it to stick open or idle high.

Have to tried cleaning the throttle body?
Have you lubed the throttle cable?
Have you checked for vacuum leaks around the TB?
Have you checked the idle control valve?
Have you checked the throttle cable adjustment?

Any luck with the idle issue? had same thing going on and tightened the ICV a few turns idle is now holding at 800 when warm.

Nope! Sadly, I’ve still got this problem going on.

I pulled my throttle body off, gave it a good cleaning, and I tried to tighten down that bypass air valve that uses a wax motor, whatever that thing’s called. It was incredibly stuck and I managed to turn it like maybe two turns at most. It seemed to help at first, because I had to unscrew the idle control a little to bring the idle up.

Then the very next day, we were back to the idle changing every single time you start the truck. It’s always steady wherever it decides to idle, but it’s going anywhere from 700rpm to 1,500rpm (all while warmed up) and I’m stumped at the moment. Been too busy lately to get in there and do more work, so I’ll post an update once I’ve done some more tests.

I know you mentioned messing with the vacuum lines on the booster fixing one issue. That, to me, tells me it's time to go through and start checking/replacing old dried out vacuum lines. The 3vz is incredibly sensitive to vacuum leaks and intake leaks. Go through through a can of brake clean (the good stuff) and spray it around vacuum lines, intake, etc and see if you can detect a change in the motor. There's DIY smoke testing setups all over the internet but I never tried them.

I have also had spark plug wires get roasted on the passenger side on my 3vz multiple times until I figured out the right way to zip tie them up. This problem would start as being intermittent then, as the cable completely fried, would become more of a problem.

lastly when is the last time it's had a tune up in general? Plugs, wires, cap, rotor? When you pulled the throttle body off for cleaning did you replace the gasket and clean the mating services?