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Discussion Starter · #1 ·
1988 7m-gte

Mods: CT26 57 trim with billet compressor wheel, 3” divorced downpipe, 3” exhaust with Apexi N1 muffler, Walbro 255 with 12V mod, cone air filter, 2.5” intercooler piping kit.

I have all of the parts to complete a lexus/550 mod, but wanted to address my high idle first.

Idles consistently around 850-900rpm. Checked the timing about a year ago and it was at 10 degrees with the Te1 and E1 connected. Idle was still around 900rpm after removing the jumper.

Several years ago in an attempt to avoid boost cut, I drilled out the plug on the stock AFM that exposes the air screw. I backed the screw all the way out, further research shows I should not have done that. What is the factory position for this screw?

I also messed with the screw on the throttle body. I now have it screwed it all the way in (clockwise). Turning it counter clockwise any speeds up the idle. What is the factory position for this screw?

At some point in time I remember this car idling around 650 rpm. I can not recall exactly when or why it changed, for some reason I think it was associated with me messing with the screws.

Any other items/area’s I should look at to try and correct my high idle?
 

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90T
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I would look for a malfunctioning idle air control valve. First do you hear it click open fully after you shut the engine off? Second, if yes to clicking, have you removed it and cleaned the pintle and checked for any junk that migh tbe preventing it from closing properly. ?
 

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Discussion Starter · #3 ·
I would look for a malfunctioning idle air control valve. First do you hear it click open fully after you shut the engine off? Second, if yes to clicking, have you removed it and cleaned the pintle and checked for any junk that migh tbe preventing it from closing properly. ?
Thanks, I will check that this weekend.
 

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1987 MA71 R154 Pearl White, Blue Velour
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1988 7m-gte

Mods: CT26 57 trim with billet compressor wheel, 3” divorced downpipe, 3” exhaust with Apexi N1 muffler, Walbro 255 with 12V mod, cone air filter, 2.5” intercooler piping kit.

I have all of the parts to complete a lexus/550 mod, but wanted to address my high idle first.

Idles consistently around 850-900rpm. Checked the timing about a year ago and it was at 10 degrees with the Te1 and E1 connected. Idle was still around 900rpm after removing the jumper.

Several years ago in an attempt to avoid boost cut, I drilled out the plug on the stock AFM that exposes the air screw. I backed the screw all the way out, further research shows I should not have done that. What is the factory position for this screw?

I also messed with the screw on the throttle body. I now have it screwed it all the way in (clockwise). Turning it counter clockwise any speeds up the idle. What is the factory position for this screw?

At some point in time I remember this car idling around 650 rpm. I can not recall exactly when or why it changed, for some reason I think it was associated with me messing with the screws.

Any other items/area’s I should look at to try and correct my high idle?
On my 87 7M-GTE, I screw the throttle screw all the way in and then back it out about 1 to 1.5 turns. (I don't know that's correct, nor have I have I ever found documentation on it).

The other thing is to recheck your timing again, it could have creeped.

When you shut your engine off, do you here the click click click click of the IAC valve?
 

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Discussion Starter · #5 ·
On my 87 7M-GTE, I screw the throttle screw all the way in and then back it out about 1 to 1.5 turns. (I don't know that's correct, nor have I have I ever found documentation on it).

The other thing is to recheck your timing again, it could have creeped.

When you shut your engine off, do you here the click click click click of the IAC valve?
Yes, when I turn the car off I hear the IAC valve click 3-4 times.

Turning the throttle screw -1-1.5 increases my idle to close to 1100.

I will check the timing again.

Thanks
 

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1987 MA71 R154 Pearl White, Blue Velour
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Yeah I'm thinking its your timing. Do your best not to move it as you tighten it down. Obvious I know but easy to do because of where the bolt is. :)
 

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Discussion Starter · #8 ·
Checked the timing and it was fine. 10 degrees with terminals connected, 12 degrees when disconnected.

Also turned the air screw in the AFM all the way in, blocking the bypass as much as possible.

Still idling high. Most recently it was closer to 1000-1100 rpm. Seems to move based on the engine and ambient temperatures.

I guess it is time to clean the IACV now. Any do's and don'ts when taking it apart to clean?
 

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Discussion Starter · #10 ·
Cleaned the IACV. It was pretty nasty. Car idled about the same afterwards, actually idled higher around 1400 for a lot longer than it typically does. It eventually settled back to the 1100 I am used to.

Should the plunger move if I turn the car to on?

I hear the IAVC click when I turn the car off, expected to see movement when I turn it on.
 

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90T
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Yes it should move. With it removed for cleaning you can see it do its thing.

Have you tried blocking off the IACV air hose. You can clamp it shut with hose pliers if its not rock hard, or just plug it with something The car should stall. It should not idle at all with the hose blocked. If it does then pirate air is coming in from somewhere else.
 

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Discussion Starter · #13 ·
Pinched the IACV air hose closed and the car did not die. Idle did not change. To be clear we are talking about the 1/2" hose that goes from the intake hose and across the engine to the IACV?

I am going to check again to see if the plunger in the IACV is moving when turning the car to ON. Did not have help the other day, might have missed the movement. I do not need to actually crank the car to see the plunger move, correct?
 

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Stock 1989 Supra Turbo w/ Sport Roof
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A shop should be able to hook a fog machine up. Or I think you can use a vape if you have one
 

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Discussion Starter · #18 ·
The most obvious leak would be the throttle plate. Pull off the pipe and see if it is closing fully
Pulled off the intercooler pipe, throttle was closing all of the way. Didn't look awful, but I took the throttle body off and cleaned it anyways, replaced the gasket while I was at it. Put it back together and now it idles even higher than before. Sitting around 1600 when warmed up.

Pinching the IACV hoses still does not stall the engine, decreases the idle but does not stall it.

I want to make sure I am understanding correctly. Pinching the IACV hose prevents air from bypassing the throttle plate regardless of if my IACV is functional or not. This indicates a vacuum leak after the throttle plate, which would be limited to the intake manifold or any of the hoses coming off of the manifold. Is that correct?

I tried testing the manifold area for leaks with starter fluid. Did not experience a change in idle. Also did not go to crazy with the starter fluid, I don't like the idea of spraying 30 year old rubbers and plastics with something so harsh. I guess my next step will be to gather what I need to do a smoke/fog test.
 

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1987 Toyota Supra
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IACV should be pulling air from the accordion hose. (When hoses are connected properly)
This is behind the AFM, so it is metered/measured air.
If you have any disconnected / cracked / leaking or hoses connected to places they should not, this will cause issues.
 

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Discussion Starter · #20 ·
Ended up getting a smoke tester to find my vacuum leak. Had smoke coming from around the injectors, turns out several of the injector grommets that sit into the head were cracked and leaking. Hoping the car idles correctly after this. Thanks for all the answers and support.

Which direction does the IACV reed/valve face? There is a metal disk side and an orange side. Which side needs to be facing the IACV plunger?
 
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