7M-GTE; Won't idle longer than 20 sec.
- Thread starter iskrem
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I tried it now, 2 hours after (?). However it is 35 celsius outside, so it is warm in Norway. 
It went up to 2000 RPM, stood there for 20-25 seconds before falling down to 1700 RPM and up to 2000 RPM, *REPEAT*. (It probably got warm fast due to temperature in the sun).
Will try again this evening when its even colder.
It went up to 2000 RPM, stood there for 20-25 seconds before falling down to 1700 RPM and up to 2000 RPM, *REPEAT*. (It probably got warm fast due to temperature in the sun).
Will try again this evening when its even colder.
Lol @ Jdub....
Idle should be around 1800-2000 when cold and the valve full open until mixture becomes leaner. It's a quick way to see if the idle path is restricted although it seems you've already done that. Frankly I think your problem lies elsewhere.
I don't wait for cold btw. I dummy the coolant sensor. It also stops the mixture from changing...
Idle should be around 1800-2000 when cold and the valve full open until mixture becomes leaner. It's a quick way to see if the idle path is restricted although it seems you've already done that. Frankly I think your problem lies elsewhere.
I don't wait for cold btw. I dummy the coolant sensor. It also stops the mixture from changing...
The only thing I can think of for the ISCV is if it's closing down on a thick layer of carbon inside the housing when it steps down after warm-up. Like JJ said, that seems to be less of a possibility.
My buddys supra was doing the same thing. It turned out to be his IAC. Get a pair of pliers and pinch the hose going to your turbo from your IAC. I did that to his and his idle went down. His IAC was seized open.
I didn't understand this. Is IAC and ISCV the same thing? What hose goes to the turbo from the ISCV? Language barrier and acronym dyslexia here.NTRA08;1320140 said:
Do you literaly mean squising it? With or without ISCV connected?NTRA08;1320185 said:
Btw, this is the acceleration wire right and the black one is for cruise control? I tighten them both a little and now the thing idles roughly at 500 RPM and up to 800 RPM after 5-10 seconds. Did I break anything?
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If the TB is fully closed at that position, it's fine. If you tightened the cable enough to open the TB plate a tiny bit, all you are doing is masking the real problem.
He has already verified the ISCV air path is clear...this is really not applicable at this point.
NTRA08;1320185 said:
He has already verified the ISCV air path is clear...this is really not applicable at this point.
Yea the TB is fully closed. I even tightend it more to see if it would improve more. TB is still closed.
Now when I start the engine when its warm it does not die. It idles rough at 500 RPM for half a minute then goes to 800 RPM. Will try tonight or tomorrow when the engine is cold to see how it perform then.
I don't want to touch the engine any more than I have to. Changing head gasket is PAIN and I never want to see whats under the hood again!
Now when I start the engine when its warm it does not die. It idles rough at 500 RPM for half a minute then goes to 800 RPM. Will try tonight or tomorrow when the engine is cold to see how it perform then.
I don't want to touch the engine any more than I have to. Changing head gasket is PAIN and I never want to see whats under the hood again!
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Both top vac ports you circled are forward of the TB plate when it's closed at idle. There is no vac at those ports at idle as a result.
I coldstarted it now without the ISCV connected. It went straight up to 1500 RPM and slowly increased to 2000 RPM where it sat for a minute or so before bungie jumping down to 1500 RPM and up to 2000 RPM and repeat.
It's supposed to do that. Why I asked before. Those symptoms prove:
1) The IDL contact is closed.
2) The ISCV stepped open on shutdown.
3) The idle speed path is unrestricted.
1) The IDL contact is closed.
2) The ISCV stepped open on shutdown.
3) The idle speed path is unrestricted.
It is a signal to the ECU by the Throttle Position Sensor (TPS)...it is either on or off. IDL on = ECU is in idle control mode.
Your TPS appears to be working correctly, at least in this respect.
Did you clean the inside of the ISCV...the valve stem and housing seat?
Your TPS appears to be working correctly, at least in this respect.
Did you clean the inside of the ISCV...the valve stem and housing seat?
As Jdub said it means "idle". The IDL contact is a switch in the TPS that tells the ECU when the throttle plate is closed. It's what's making your engine rev up and down but it's not the cause of your problem.
When the idle speed valve is working idle problems are caused by the switch being open. You have the opposite situation (switch working, valve not) but the result is going to be the same: unstable idle. In the first case bad idle is cause by the idle speed control system being disabled (by the open IDL switch) while in the second case it's caused by a safety function coded into the ECU. If rpm becomes too high with the throttle closed the ECU cuts fuel injection because that's an illogical situation the TCCS deems as potentionally dangerous. It's one way the box keeps tabs on itself. Injection is restored when rpm falls a few hundred rpm below the cutoff point and the cycle repeats.
With the ISCV full open there's enough volume (conductance in engineering parlance) in the idle bypass path to allow rpm to exceed this cutoff point. The mixture is also richer when cold. However when the ISCV is working correctly it begins to step closed (as soon as rpm crosses 500 just after start) on it's way to setting whatever target rpm is required for the current coolant temperature. Put another way the engine normally doesn't reach the rpm cutoff point on a cold start regardless of ambient and even if it does won't stay there long enough to trigger the safety cut. Yours is. If you unplug the TPS or hold the throttle slightly open the hunting should disappear because rpm and throttle position will then "jive" and make the ECU happy.
Anyway, the solution is to determine why 1) the valve isn't stepping closed after engine start or 2) it is stepping closed but something else is keeping idle rpm above the cutoff point.
When the idle speed valve is working idle problems are caused by the switch being open. You have the opposite situation (switch working, valve not) but the result is going to be the same: unstable idle. In the first case bad idle is cause by the idle speed control system being disabled (by the open IDL switch) while in the second case it's caused by a safety function coded into the ECU. If rpm becomes too high with the throttle closed the ECU cuts fuel injection because that's an illogical situation the TCCS deems as potentionally dangerous. It's one way the box keeps tabs on itself. Injection is restored when rpm falls a few hundred rpm below the cutoff point and the cycle repeats.
With the ISCV full open there's enough volume (conductance in engineering parlance) in the idle bypass path to allow rpm to exceed this cutoff point. The mixture is also richer when cold. However when the ISCV is working correctly it begins to step closed (as soon as rpm crosses 500 just after start) on it's way to setting whatever target rpm is required for the current coolant temperature. Put another way the engine normally doesn't reach the rpm cutoff point on a cold start regardless of ambient and even if it does won't stay there long enough to trigger the safety cut. Yours is. If you unplug the TPS or hold the throttle slightly open the hunting should disappear because rpm and throttle position will then "jive" and make the ECU happy.
Anyway, the solution is to determine why 1) the valve isn't stepping closed after engine start or 2) it is stepping closed but something else is keeping idle rpm above the cutoff point.
I have two ISCV. I checked the one not in the engine, hooked up the middle wires with + and touched the other four one at a time with -. I could hear a "click", but the valve (thingy in the middle) does not move.
Will check the ISCV in the car as soon as I can to check result.
Will check the ISCV in the car as soon as I can to check result.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=107
Yours appears to be stepping open when the engine is shut down but not stepping closed. Could be a broken wire or bad pin at the connector. Either that or it failed open but yes, you need to check it. No need to install into the manifold. Just plug it in. Since it can't effect rpm when not installed it'll step fully closed. A cable tie around the end of the pintle will amplify movement. Even if it works you should remove the motor cover and check the lead screw, stop plate, and bearings. Lube if needed. Course, if the motor is fried it's done for. If the valve checks out test the wiring. If the wiring checks out one or more drivers in the ECU are blown. Rare but it does happen, especially if the wiring got shorted at some point...
Yours appears to be stepping open when the engine is shut down but not stepping closed. Could be a broken wire or bad pin at the connector. Either that or it failed open but yes, you need to check it. No need to install into the manifold. Just plug it in. Since it can't effect rpm when not installed it'll step fully closed. A cable tie around the end of the pintle will amplify movement. Even if it works you should remove the motor cover and check the lead screw, stop plate, and bearings. Lube if needed. Course, if the motor is fried it's done for. If the valve checks out test the wiring. If the wiring checks out one or more drivers in the ECU are blown. Rare but it does happen, especially if the wiring got shorted at some point...