90wpickup

'90 Pickup with a 3VZE, auto. would surge when stopped and idle high when in park or neutral. In searching it sounded like a low coolant or plugged coolant line in the TB. I replaced the radiator because it was leaking. With full coolant the problem remained. So took the TB off and sure enough the coolant passage was clogged. Cleaned it out good, put it back together and now it will barely idle. Turning the idle adjustment screw has little or no effect on the idle speed. I can keep it running by opening the throttle but it won't idle. Any ideas? Thanks.

OutlawMike

If you adjust the idle screw and are getting little to no change in idle, then, air is going around the throttle body somewhere else.

The valve in that coolant passage (behind that small metal plate on the TB) could be bad. It might be stuck open. I adjusted mine a little when I was in there to make it close a bit more. It uses some type of spanner wrench to adjust, but I just tapped it on one of the spanner flats with a screw driver, it moved fairly easily.

I am not saying that is your problem, but it is one place to look. You will want to make sure there are no major vacuum leaks causing the air to bypass and making he idle screw have little affect.

Also, are you sure that the hoses or pipes running to the TB coolant passage are not clogged? If they are clogged you might not be getting enough flow in there to make that valve close. It needs to have hot engine coolant on it to close down after warm up. If the hoses or pipes are clogged, no flow, and it runs cold. I blew into the pipes and/or hoses with compressed air when I had my throttle body off.

You get really good at swapping coolant out of the motor with these problems.....

ibeamtaco

vacume leak

ibeamtaco

spray tb and around tb with carb clean when it changes you found leak

90wpickup

The coolant hoses to the TB are clean, I took them off w. the TB. I think coolant is flowing because the hose get warm while it didn't before. I also think the valve is working because it will idle when it is stone cold, as it warms up a bit it won't idle, so I'm thinking the valve is closing as it warms up.

I'll check for vacuum leaks. I didn't replace the TB gasket as this turned into a Sunday job and I didn't plan ahead too well. I know the gasket is torn, would that cause enough of a leak to cause it not to idle?

Another question, should the throttle plate close against the wall of the TB or should it hit the stop screw? Mine stops against the TB wall. I'm wondering if sometime before I bought the truck somebody mis-adjusted the stop screw while trying to fix a high idle problem caused by the clogged coolant passage.

Thanks for the suggestions.

ibeamtaco

yeah the crack in gasket can make it leak and it hitting the screw would only make it idle higher
i just by the sheets of gasket material and make my own gaskets

OutlawMike

The torn gasket could be causing your vacuum leak, especially if it is a big opening.

The throttle plate should just about close against the wall of the TB. You don't want it to jam in there, so it should just touch, or slightly hover. It really does not matter if it is just touching or not, as long as it is in a position that allows the idle adjustment screw to get the idle where it needs to be.

In your case, with the throttle plate all the way down against the TB bore and the idle screw all the way in, you still have a high idle. So, you have a vacuum leak somewhere. Hard to find them sometimes, they can be a pain.

Good luck.

90wpickup

I guess I wasn't clear in my posts. The idle is not high anymore, it is way to low to the point where it will stall without holding the throttle open after it warms up a bit. When cold it starts fine and will idle albeit too slow, after it warms up a little it will not stay running without holding the throttle open.

OutlawMike

Well, it is pretty easy to adjust the throttle stop out to open the plate a bit. It sounds like you are on the bottom end/past the adjustment range of the idle adjustment screw. If you can make it idle fine by opening the throttle a touch, then, adjust the throttle stop out to get it into a range where the idle adjustment screw will allow you to fine tune the idle.

Two things to watch out for:

When you adjust the throttle stop, then you will need to verify the TPS settings with an Ohm meter. Most likely you will need to adjust the TPS.

Also, the O Ring on the idle adjustment screw dries out over time and leaks air. Since your idle is all messed up anyway, get a new O-ring for that screw, just back it all the way out and pop it out of the TB. You can probably find one at your local hardware store that will fit.

Sorry for the confusion, it does not sound like you have a vacuum leak. Given what you said above, it seems your throttle plate is out of adjustment.

Good luck.

Mike

90wpickup

That's for sure, when I tried to remove the O ring it just broke. Found a new one and replaced it. I have ordered a new TB gasket, my local dealer didn't have any in stock (even called my poor truck "so old"), so this weekend the TB is coming off again for cleaning, adjusting the throttle plate and checking/adjusting the TPS. Hopefully this will correct my low idle.

Thanks for you help. I'll report my results.

jdwilson

Just pulled my throttle body for a good cleaning. It took me longer to clean old gasket from plenum than to clean TB i suggest some permatex gasket remover and a few good razor blades. 89 4runner 3vze 253,000 miles

90wpickup

Well I took the TB off again, cleaned it, adjusted the throttle plate stop screw, tested and adjusted the TPS and replaced the TB gasket. Still no difference, it will barely idle when it warms up a little then surges until it stalls out. I did get it to idle by turning the throttle stop screw in further than it should be but when it is in drive with the brakes on it will surge and stall. Funny thing is when it is in reverse it seems to idle OK, but in drive it craps out. I'm giving up on it, now I need to find a good shop to take it to. Anyone care to recommend a good shop in the Torrance, CA area, preferably not a dealer?

testement

did u ever get that figured out 90wpickup? i am having a similar problem and was just wondering what it was ...thanks

90wpickup

I did figure it out, or I should say it was pointed out to me. The air inlet boot was cracked where it goes on the throttle body. This allowed un-metered air in, thus it was way lean and wouldn't idle. I knew it was cracked, I could see it, but it was under the clamp and I thought the clamp was still sealing it, wrong.... New boot and all was well. Check for any air leaks past the MAF sensor, I should of done that first, but hindsight is always 20-20.

Gevo

I am trying to find out what/how to adjust that passage way valve... seems not many people go in this far...

I know this is old post, so if you're around.. any pointers will be appreciated

MudHippy

Probably because there's no reason to. Since it's not ever going to become misadjusted. Hence why there are no specifications for adjustment.

Gevo

Well the open nut that screws around it and pushes it down must have some specific
Torque value. I had to take it all apart to clean it.. it was imobile until I cleaned the gunk out. Toyota dealer was no help.

MudHippy

I wouldn't think so. The only requirement is that the valve be fully closed when the engine is at operating temperature(or more specifically, when the engine coolant temperature is approx. 80°C/176°F or above). Which doesn't necessitate any specific torque value. Just that it be in the correct position relative to the gate valve to allow that to happen when it should.

See page 8 of this pdf.
http://www.autoshop101.com/forms/h21.pdf

Gevo

Thanks for that link! I will read the relevant parts.. if I understand its operation im sure ill figurebout what to do.

Nissanclubman

No it shouldn't. The correct position is to back off the stop screw and allow the butterfly to rest against the inside of the TB then tighten up the stop screw until it just touches the butterfly stop arm, then give it 1/2 turn to lift the butterfly off the TB. Lock that in place then check the that Throttle position sensor is adjusted correctly.