4age high engine idle

[ssspacely]

I have had this problem for a long time now. Trying to sort it out. I took apart the throttle body and cleaned it up real well. The engine idles at an even higher RPM now (around 2.5 to 3k rpms.

Does this look right? I see this open hole in the back of the throttle body where it meets the intake manifold.



It looks like the other end goes to the inside of the throttle body after the MAF sensor.



I am thinking this could be the reason why my car idles too high

[ssspacely]

Can someone tell me how to post pictures? Thanks.

[BakaBaka]

To post pictures, upload it to any free image hosting sites (eg: imgur, photobucket, imageshack.. etc) then link those photos onto your post. You can't upload photos from your computer onto this forum since it's a forum.. not an image hosting service.

Have you checked the butterfly plate in your throttle body? If theres too much crud/carbon buildup.. it can prevent the plate from fully closing.. allowing air in and tricking the TPS that you're stepping on the gas.. effectively raising the RPM up. A faulty or dirty idle air control valve can cause erratic and high idling too. Pictures would be nice to reference what you're talking about.

Also.. make sure your idle mixture screw is adjusted properly.. maybe your friend decided to pull a prank on you and messed with the screw?

[ssspacely]

original post edited. I cleaned the throttle body out pretty well. The butterfly seems to close well. I closed the idle screw all the way and the engine still idles way high. I am trying to eliminate all the simple things before spending $150 on a new idle air control valve.

[BakaBaka]

Before you waste money on a replacement. Take off the idle air control valve below the throttle body. Should be a couple of screws, get some brake or carb cleaner and shoot it in every passageway you find on the IACV. I had high idling issues before due to the IACV being clogged by coolant gunk.

As far as the throttle body goes on your pictures, everything looks as it should.

[MisterJerk]

i dont think thats the right TB. Im going to take a look at mine now. I swear that hole is supposed to be on the other side of the the throttle body for the crank case vent or EGR.

[MisterJerk]

I have the exact same TB on mine. i did not take the inlet off to look inside though.

i don't think these cars idle high with a vac leak due to the MAF/AFM(unmetered air makes em die) before you check the Throttle pos sensor and throttle cable, have you done anything witht the idle air adj screw?

[ssspacely]

BakaBaka I have taken apart the IACV and cleaned it. The idle problem persists. I have basically verified that the idle problem is due to the IACV not working properly. I did the simple test of warming up the car then plugging the hole in the throttle body. After that the car would idle fine with some adjusting on the idle air adjusting screw. I may take the throttle body apart and try to clean it again. I may even soak the IACV for a while to see if that will loosen it up.

[BakaBaka]

BakaBaka I have taken apart the IACV and cleaned it. The idle problem persists. I have basically verified that the idle problem is due to the IACV not working properly. I did the simple test of warming up the car then plugging the hole in the throttle body. After that the car would idle fine with some adjusting on the idle air adjusting screw. I may take the throttle body apart and try to clean it again. I may even soak the IACV for a while to see if that will loosen it up.

Well.. at least now you know which is the defective part. Rarely does the IACV fail on our cars.. usually.. a quick clean makes it work again. But then again, I digress.. these cars and it's counterparts are 25+ years old already. Good luck with your endeavor.

[apsogosGTi]

the iscv failed on my car at 250.000 kms , i replace it with a new one.... ( yes i tried to fix the old one but nothing)

[jondee86]

i dont think thats the right TB. Im going to take a look at mine now. I swear that hole
is supposed to be on the other side of the the throttle body for the crank case vent or EGR.

Give this man a cigar He is on the money !!! You have got a FWD throttlebody bolted to
a RWD manifold. That means two things... you are leaking unmetered air into the engine,
and your cam cover vent is blocked and no longer venting in front of the throttle butterfly.
There is a tiny bleed hole into the manifold from the vent channel cast into the side of the
manifold, but that can't handle venting all the blowby. The result is that your engine will
pressurize with many possible cool side effects, such as oil leaks, dipstick blowing out,
smoke from the exhaust or even crank seals blowing out.

Easiest cure is probably to JB Weld the hole that is leaking air, and then plug the cam cover
hose inlet to the manifold. Take a new hose from the cam cover and connect it into the
intake ducting somewhere between the AFM and the throttlebody.

Cheers... jondee86

[jondee86]

... I have taken apart the IACV and cleaned it. The idle problem persists.

Here are a couple of simple checks that you can make...

Check that both hoses from the engine cooling system to the valve get
hot with the engine running. If one stays cool. the water is not circulating.
Check the hoses are not blocked.

Remove the valve and clean it. Make sure there is a clear flow from
inlet to outlet on the two water hose connectors. These can get blocked
with corrosion or other crud... poke a piece of wire or similar into each
tube and keep working until you can blow thru either tube and know it is
clear. Carb cleaner or WD40 whatever does not work to remove corrosion
on the water side. But it will help clean the black crud from the air side.

Drop the whole valve into a pan full of boiling water and see if the valve
moves about 8 mm. If the valve opens and closes as it should, re-install
with a new gasket and test. If the valve does not open and close, get
another valve and check as above before installing.

Cheers... jondee86

[ssspacely]

Hey all. Revisiting this from over a year ago. Been driving the car with the racing idle all last summer. Want to solve it for sure this time.

I replaced the IACV with a brand new valve. Still the idle races. Checked all of the vaccum lines and they all look good visually. My questions are:

Would the ac compressor cause the high idle? My compressor is rusted and not working. I tested it last summer and the compressor leaks like a sieve. I got it to spin for a minute and the noise from the compressor sounded like nails on a chalkboard. I have a new compressor to swap in.

2. How can I check the electronic idle up for the ac?

3 how can I check the metal vaccum lines behind the motor?

4 if there is a lot of carbon built up in the intake manifold , can that cause a high idle? Is it possible the tvis is stuck open?

5 is it possible the intake mani gasket is leaking causing the high idle?

I have spent a bunch of money already on parts that didn't seem to fix the problem. Thank for the help. I have for the passed year researched high idle problems on the forums and I still can't figure it out. You guys are great about giving advice though. Thanks

[jondee86]

If you look here.... AE86 16V - Throttlebody - TECH
you will see the connections on the IAV for the power steering. In normal operation
air passes OUT thru one tube and IN thru the other to raise the idle when the power
steering is under load.

Often, when the P/S has been deleted, these two tubes are looped together with a
short piece of hose, and this results in a permanently high idle. These two tubes must
be capped off individually when P/S has been deleted.

If the P/S idle-up hoses are leaking, or disconnected with an open end, you will also
get a permanently raised idle. Check these things first.

Cheers... jondee86

[ssspacely]

Power steering checked out. Hoses are in good shape and clear. I did however try to blow air through the two hoses at the ps pump but could not. Is that normal?

I can move air through these tubes and the hoses are tight.

I cannot move air through the power steering pump

Let me know if you can view the pictures. Uploading from my phone and not sure if I did it right.

[yoshimitsuspeed]

This is why you diagnose the problem first and then buy the parts you need instead of buying parts and hoping.

The easiest thing to do is temporarily cap off all your vacuum line ports on the mani. Cap them with little rubber plugs. The only one I wouldn't leave capped for the whole diagnostic process is the FPR reference. I would cap that one, see if the idle changes and then hook it back up. Cap all the others like brake booster, idle up valves, charcoal cannister, EGR, VVT, etc and put little vacuum caps on all ports on the mani and throttle body.
If the idle goes down to normal then hook the vacuum lines up one at a time and see which one/s makes the idle increase.
If the idle is still high move on to looking for vacuum leaks. Make sure the throttle plate is closing all the way etc. If it's idling above 1600 RPM when warm and isn't surging then you have other problems. It could mean your TPS isn't adjusted properly. It could mean something is holding the throttle plate open a little or it could mean your temp sensors aren't working properly.
Check for intake leaks. I prefer the boost type test where you use a coupler, regulator and air compressor to pressurize the intake to 10-15 PSI and then use soapy water to check for leaks. Make sure to use a regulator and only about 15 PSI max.
This is safer than spraying flammable stuff like brake clean, propane etc on a running motor.
Check around all your gaskets.
I am not familiar with the longitudinal intake mani but that hole on yours doesn't look right. Have you taken the TB off to see what it looks like? Maybe transverse TB on a longitudinal mani or something like that?

[ssspacely]

The picture of th TB in my previous post is not on my car. It was from a spare but it was easier to take a picture of that than to take my TB off the car.

I have taken the throttle body apart and cleaned it thoroughly. I capped the port from the IACV on the inside of throttle body and the idle came down to normal. I thought that was the diagnosis so I bought a new IACV. I cleaned the old one and I am pretty sure it works fine. So now I have a spare.

I will conduct the tests from yoshimitsuspeed. Where can I find a vacuum diagram? I don't want to miss anything. It must be a vacuum leak or plug somewhere .

I could see some benefits to cleaning out the intake plenum. Do you think that a leak in the plenum gasket between the head and the plenum would cause the high idle?

[yoshimitsuspeed]

The picture of th TB in my previous post is not on my car. It was from a spare but it was easier to take a picture of that than to take my TB off the car.

I have taken the throttle body apart and cleaned it thoroughly. I capped the port from the IACV on the inside of throttle body and the idle came down to normal. I thought that was the diagnosis so I bought a new IACV. I cleaned the old one and I am pretty sure it works fine. So now I have a spare.

It sounds to me like you have found the source of the problem. Now you just need to find the cause. If your idle came down when you capped the IACV I would focus on that circuit first.
You tried replacing the valve and nothing changed so that's not likely the problem. Is it getting coolant flow? When the motor is at operating temp does the coolant flowing through the valve feel like it's at operating temp?

I could see some benefits to cleaning out the intake plenum. Do you think that a leak in the plenum gasket between the head and the plenum would cause the high idle?

Any leak after the throttlebody will cause high idle.

http://matrixgarage.com/articles/unders ... l-jetronic

[ssspacely]

The picture of th TB in my previous post is not on my car. It was from a spare but it was easier to take a picture of that than to take my TB off the car.

I have taken the throttle body apart and cleaned it thoroughly. I capped the port from the IACV on the inside of throttle body and the idle came down to normal. I thought that was the diagnosis so I bought a new IACV. I cleaned the old one and I am pretty sure it works fine. So now I have a spare.

It sounds to me like you have found the source of the problem. Now you just need to find the cause. If your idle came down when you capped the IACV I would focus on that circuit first.
You tried replacing the valve and nothing changed so that's not likely the problem. Is it getting coolant flow? When the motor is at operating temp does the coolant flowing through the valve feel like it's at operating temp?

I could see some benefits to cleaning out the intake plenum. Do you think that a leak in the plenum gasket between the head and the plenum would cause the high idle?

Any leak after the throttlebody will cause high idle.

http://matrixgarage.com/articles/unders ... l-jetronic

OK I read through your most on matrix garage. In particular this part is interesting to me. "In the TPS there is a sensor (really just an on off switch). When the car is idling and no throttle is being applied this switch is triggered telling the ECU the car is idling and to behave as such. The ECU has a limit set into it that idle speed should never go over. On the 4A-GE and 4A-GZE This is approx 1600 RPM. If the RPMs hit this limit while the idle circuit is tripped the ECU will cut fuel until the RPMs drop to an acceptable level causing a surging idle.".

Let me explain what my engine does a little more. It has trouble starting when cold. Nearly every time I start the car it takes 3 turns of the key to start. First turn of the key and the engine will just crank and not start. Second turn and the engine will chug a couple of times and then die. Third turn and the engine will start. It will run rough for a couple of seconds until the idle picks up to around 2200 rpms or so. The engine will stay there until warm where the idle will the increase to 3000rpms on occasion.

So my question is two fold. Why would the engine struggle initially to start? Once started and warm, why does sensor in the tps not cut fuel when the engine idles above 1600rpm as described above?

I have completed the test by plugging the port on the inside of the throttle body and the engine will idle normal. I Dont understand why the high idle is not limited by the ecu to 1600. Pretty confused still. Should be able to diagnose more this weekend. Thanks

[yoshimitsuspeed]

If the ECU is not cutting fuel at 1600 then either the ECU doesn't know the motor is warm, the TPS is out of adjustment or bad, Something is holding the throttle plate open so the TPS is not reading closed because the idle circuit is not tripped.
Test your temp sensors, make sure your throttle plate is closing all the way and test your TPS and adjust it if necessary.

As for why it has trouble starting? Could be any number of things. Go through the FSM troubleshotting for related issues. Most people will suggest to check the CSI. It's not a bad idea but I have started my GZE in -30f without issues. Many other people have run without it on NA and GZE.

[jondee86]

I capped the port from the IACV on the inside of throttle body and the idle came down to normal.

While this ^^^^ test appears to accurately pinpoint the source of your high idle, it is necessary
to clarify a few things before going further down this line of diagnosis....

1. When the engine is warmed up and the ISCV port is blocked, the engine idles @ what rpm ??
2. When the engine is cold and the ISCV port is blocked, will the engine start ??
3. If the cold engine starts with the port blocked, it idles @ what rpm ??
4. If the cold engine starts and idles, as it warms up the rpm rises to what rpm ??
5. Does the idle speed ever drop down as the engine is warming up ??
6. Does the idle speed change when the A/C clicks ON ??
7. Does the idle speed change when you turn the lights ON or step on the brakes ??
8. Have you checked the ignition timing with the ISCV port blocked (diagnostic port not jumped) ??

Contrary to popular opinion, there are no evil demons inside your engine that play tricks on you.
Idle speed is essentially controlled by the amount of air that gets into the engine, ignition timing
and temperature. There are of course many different things that can mess with your idle, but if
your statement quoted above is accurate, you have eliminated 95% of them.

Cheers... jondee86

[ssspacely]

I capped the port from the IACV on the inside of throttle body and the idle came down to normal.

While this ^^^^ test appears to accurately pinpoint the source of your high idle, it is necessary
to clarify a few things before going further down this line of diagnosis....

1. When the engine is warmed up and the ISCV port is blocked, the engine idles @ what rpm ??
2. When the engine is cold and the ISCV port is blocked, will the engine start ??
3. If the cold engine starts with the port blocked, it idles @ what rpm ??
4. If the cold engine starts and idles, as it warms up the rpm rises to what rpm ??
5. Does the idle speed ever drop down as the engine is warming up ??
6. Does the idle speed change when the A/C clicks ON ??
7. Does the idle speed change when you turn the lights ON or step on the brakes ??
8. Have you checked the ignition timing with the ISCV port blocked (diagnostic port not jumped) ??

Contrary to popular opinion, there are no evil demons inside your engine that play tricks on you.
Idle speed is essentially controlled by the amount of air that gets into the engine, ignition timing
and temperature. There are of course many different things that can mess with your idle, but if
your statement quoted above is accurate, you have eliminated 95% of them.

Cheers... jondee86

So when I conducted the test by capping the port, I did it when the engine was warm. So I cannot answer questions 2 or 3. I will have to revisit that this weekend. I can answer your other questions though.

1. With the IACV port capped and engine warm it will idle at 800rpms after adjusting the idle screw. I have the idle screw totally closed to drive the car so I actually had to open the idle adjustment screw a bit to keep the car from stalling when it was totally closed and the port capped.

2 and 3 I will test when I get a chance.

4. Without the IACV port capped the engine will start and idle around 2200 to 2500 rpms. When it warms the idle usually climbs to around 3000. But it does vary. depends on the ambient temperature.

5 the idle speed never drops down as the engine warms. It always climbs.

6 the AC is inoperable due to leaks in the refrigerant circuit and a toasted compressor. Switching the AC on does nothing to the idle.

7 the idle speed DOES increase when stepping on the brakes. I do not notice a difference when I switch the lights on. It is hard when the engine idles so high.

8 i have not checked this but that is a great idea.

Sorry I don't have a lot of answers right now but I wanted to tell you what I know right now. When I get a chance to perform the other tests I will update. I know there is a fix to this and monsters under the hood do not exist to drive me crazy. this is awesome help too. thanks guys for giving me good ideas to test. Troubleshooting is actually fun for me when there are results.

[jondee86]

1. With the IACV port capped and engine warm it will idle at 800rpms after adjusting the idle screw.
I have the idle screw totally closed to drive the car so I actually had to open the idle adjustment screw
a bit to keep the car from stalling when it was totally closed and the port capped.

This really tells me all I need to know as far as confirming the cause of the high idle...
your IACV (AAV) is not working. The IACV is staying wide open and not responding to any
change in engine temperature. This gives you a starting idle of around 2200rpm. The normal
rise in idle speed due to better fuel atomization in a warm engine accounts for the further
rise in idle speed to 3000rpm (+/-) on a fully warmed up engine. The A/C idle-up only
becomes active when the A/C compressor kicks in, so that is eliminated, and the electric
load idle-up appears to be working. However, that will only contribute a rise is idle speed
of around 200rpm when it kick in.

Thus, the cause of the high idle is quite clear. As previously stated, it only remains to figure
out why neither of your ISC Valves is working. The air passage thru the valve is obviously
working, but the valve does not close. Hot water from the cooling system must flow thru the
water section of the valve to heat the wax capsule and close the valve. Therefore, the two
metal tubes that dome out from under the intake manifold and connect to the two small rubber
hoses that connect to the ISCV, need to be checked to see if they get hot. when the engine
heats up. If only one tube gets hot, and the other one stays cold... something is blocked.

Start by pulling the hoses and seeing if there is a lump of silicone or some other accumulated
crud blocking a hose or the tube it attaches to. Keep going until you find out where the water
side is blocked. If hot water does flow thru the valve and it still does not close... your ISCV
is not working. Take it off and test it in a pan of boiling water. There is absolutely no need to
look anywhere else for a solution to your high idle !!!!

Cheers... jondee86

[ssspacely]

1. With the IACV port capped and engine warm it will idle at 800rpms after adjusting the idle screw.
I have the idle screw totally closed to drive the car so I actually had to open the idle adjustment screw
a bit to keep the car from stalling when it was totally closed and the port capped.

This really tells me all I need to know as far as confirming the cause of the high idle...
your IACV (AAV) is not working. The IACV is staying wide open and not responding to any
change in engine temperature. This gives you a starting idle of around 2200rpm. The normal
rise in idle speed due to better fuel atomization in a warm engine accounts for the further
rise in idle speed to 3000rpm (+/-) on a fully warmed up engine. The A/C idle-up only
becomes active when the A/C compressor kicks in, so that is eliminated, and the electric
load idle-up appears to be working. However, that will only contribute a rise is idle speed
of around 200rpm when it kick in.

Thus, the cause of the high idle is quite clear. As previously stated, it only remains to figure
out why neither of your ISC Valves is working. The air passage thru the valve is obviously
working, but the valve does not close. Hot water from the cooling system must flow thru the
water section of the valve to heat the wax capsule and close the valve. Therefore, the two
metal tubes that dome out from under the intake manifold and connect to the two small rubber
hoses that connect to the ISCV, need to be checked to see if they get hot. when the engine
heats up. If only one tube gets hot, and the other one stays cold... something is blocked.

Start by pulling the hoses and seeing if there is a lump of silicone or some other accumulated
crud blocking a hose or the tube it attaches to. Keep going until you find out where the water
side is blocked. If hot water does flow thru the valve and it still does not close... your ISCV
is not working. Take it off and test it in a pan of boiling water.

Cheers... jondee86

But then why does the TPS not cut the fuel when the idle is above 1600 rpm? Does that mean the TPS is not adjusted properly?

The IACV is brand new from Toyota. I was surprised they still had one. I know the engine cooling system is working. The car warms up fine and the thermostat is new.

I will check all the hoses as you said. Something doesn't seem to add up though.

[yoshimitsuspeed]

But then why does the TPS not cut the fuel when the idle is above 1600 rpm? Does that mean the TPS is not adjusted properly?

Either you have more than one problem or somehow the problem is related.

It could be that you don't have coolant running through the IACV and the TPS is not adjusted properly.
It could be that coolant is not running through the IACV and your temp sensor is not working properly to tell the ECU the motor is warm.
Or you could have a complete circuit bypassed or blocked off where the warm coolant was not flowing past the temp sensor or the IACV.
I am trying to think if it would be possible for this to happen while still having coolant flowing through the radiator. I think it wold have to flow past the temp sensor to flow through the radiator. Unless of course someone has tampered with the plumbing.

Whatever the case it is very likely that your issue is related to some combination of those components but could also include others.

[jondee86]

But then why does the TPS not cut the fuel when the idle is above 1600 rpm?
Does that mean the TPS is not adjusted properly?

Very likely. But don´t go side-tracking yourself. Get the ISCV working correctly and then
worry about the reason fuel cut does not occur. If fuel cut was happening you would be
waaaaaaayyyy more pissed about high idle than you are now

Cheers... jondee86

[Deuce Cam]

Sorry I didn't read the whole thing. Does the idle bounce when the engine is warmed up?

My first ae86 had a warm bouncing idle from 1500-2000 rpm (people thought I was trying to race them at stop lights). I installed a brand new iacv and the problem persisted. Then I tried plugging the iacv hole in the throttle body and the warm idle dropped to 1000 rpm and was steady. Further investigation revealed that there was a clog in the metal hard line leading to or from the iacv. The flow of coolant was too restricted for the iacv to operate correctly.

First thing I would check is the soft coolant lines coming off the iacv to make sure they're both getting hot.

[ssspacely]

But then why does the TPS not cut the fuel when the idle is above 1600 rpm? Does that mean the TPS is not adjusted properly?

Either you have more than one problem or somehow the problem is related.

It could be that you don't have coolant running through the IACV and the TPS is not adjusted properly.
It could be that coolant is not running through the IACV and your temp sensor is not working properly to tell the ECU the motor is warm.
Or you could have a complete circuit bypassed or blocked off where the warm coolant was not flowing past the temp sensor or the IACV.
I am trying to think if it would be possible for this to happen while still having coolant flowing through the radiator. I think it wold have to flow past the temp sensor to flow through the radiator. Unless of course someone has tampered with the plumbing.

Whatever the case it is very likely that your issue is related to some combination of those components but could also include others.

I also replaced the temp sensor as it was broken.

Other things I have done:

replaced the thermostat since it was non existant when I bought the car. replaced the temp sensor, the IACV and some of the broken vacuum lines. The car runs much better than it did when I bought it other than the high idle.

duececam. The idle does not bounce. It is steady but high.

Jondee. I am pretty certain the hoses to the iacv get hot. But maybe not hot enough and maybe not enough flow. Could that do it? I have to spend more time on this. Damn day job gets in the way of what I really want to work on.

This is all very encouraging. I can't wait for this weekend.

[yoshimitsuspeed]

You don't have an IR temp gun do you?
If the IACV is getting hot to the touch I would think idle should change noticeably even if it wasn't getting as hot as the rest of the system.
If you have an IR gun I would check the circuit and see if it is much cooler at the TB than the thermostat housing.

[Deuce Cam]

In my case one of the lines didn't quite seem to be getting hot. I would have assumed the iacv itself was clogged if it wasn't brand new. Then I got to thinking... not much coolant came out when I disconnected the lines to swap iacv's. Normally those lines should flow a lot of coolant if disconnected. On that engine I just ended up installing an iacv delete plate since I didn't feel like trying to clear the lines. That fixed my idle issues... aside from cold starts...