Idle stuck at 3,4k rpm.
12-29-2017, 04:43 AM
#1
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Idle stuck at 3,4k rpm.
Del Sol 1992 ZC swap
I wasnt driving it a lot for the past 2 months, maybe once/twice a week. Got in the car this morning, ran fine for few mins, tried to stop and it just stuck rpm at 3k rpm, tried giving it some gas, it went up to 3.5k. Turned it off then back on, same thing, went under the hood, disconnected IACV, works fine.
It's not throttle cable and IACV is like 6 months old as well as TPS. When RPM's go high, TPS is still reading 0.5v. It's not vacuum leak I guess? Otherwise it would do the same thing if IACV is connected/disconnected. Or I'm entirely wrong?
Dont know what to look at. Could it be IACV? Thanks guys.
I wasnt driving it a lot for the past 2 months, maybe once/twice a week. Got in the car this morning, ran fine for few mins, tried to stop and it just stuck rpm at 3k rpm, tried giving it some gas, it went up to 3.5k. Turned it off then back on, same thing, went under the hood, disconnected IACV, works fine.
It's not throttle cable and IACV is like 6 months old as well as TPS. When RPM's go high, TPS is still reading 0.5v. It's not vacuum leak I guess? Otherwise it would do the same thing if IACV is connected/disconnected. Or I'm entirely wrong?
Dont know what to look at. Could it be IACV? Thanks guys.
12-29-2017, 06:28 AM
#2
Re: Idle stuck at 3,4k rpm.
If the ECT tells the ECU that the engine is cold, it will open the IACV and make it idle fast. Since it slowed down when you unplugged IACV, something is making the ECU drive the IACV open.
So, check your ECT sensor with an ohmmeter. They can be out of calibration but not far enough to throw a code.
So, check your ECT sensor with an ohmmeter. They can be out of calibration but not far enough to throw a code.
12-29-2017, 07:03 AM
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Re: Idle stuck at 3,4k rpm.
If the ECT tells the ECU that the engine is cold, it will open the IACV and make it idle fast. Since it slowed down when you unplugged IACV, something is making the ECU drive the IACV open.
So, check your ECT sensor with an ohmmeter. They can be out of calibration but not far enough to throw a code.
So, check your ECT sensor with an ohmmeter. They can be out of calibration but not far enough to throw a code.
Temp was around 70-80 celsius when it happened. It dropped to 900, bounced to 1200, dropped back to 900 and from that moment on, it just stuck at 3k regardless if the clutch is in or out (almost had a crash, couldnt slow down and wasnt aware it's still stuck at 3k)... ECT is new as well, brand new.
12-29-2017, 04:26 PM
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Re: Idle stuck at 3,4k rpm.
Not sure if this is your engine's situation but my car's engine's throttle blade would stick on return to resting positiion (closed). I was told that over-time and use the shaft gets worn and bends down very slightly causing the blade to scrape or catch on the bottom of the TB's bore. I use a thin layer of sythetic grease (ex:Napa Syl-Glide) on the blades perimeter edge and bit on the area of the TB bore where the throttle blade rests in the closed position. I also spray a bit of WD-40 on the spring and shaft that is located behind the throttle pulley (ear). I've been maintaining it like this around every three or four months and no issues within the past year.
Also, make sure throttle cable tension is correct. Another thing to check is that the perch(s) that the throttle cable fits in aren't causing binding.
IIRC someone had a similar situation in the recent past, repalced the thermostat and it corrected the issue. However, I can't confirm this as I don't accuratley recall where I read it.
Also, make sure throttle cable tension is correct. Another thing to check is that the perch(s) that the throttle cable fits in aren't causing binding.
IIRC someone had a similar situation in the recent past, repalced the thermostat and it corrected the issue. However, I can't confirm this as I don't accuratley recall where I read it.
12-29-2017, 05:06 PM
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Re: Idle stuck at 3,4k rpm.
Not sure if this is your engine's situation but my car's engine's throttle blade would stick on return to resting positiion (closed). I was told that over-time and use the shaft gets worn and bends down very slightly causing the blade to scrape or catch on the bottom of the TB's bore. I use a thin layer of sythetic grease (ex:Napa Syl-Glide) on the blades perimeter edge and bit on the area of the TB bore where the throttle blade rests in the closed position. I also spray a bit of WD-40 on the spring and shaft that is located behind the throttle pulley (ear). I've been maintaining it like this around every three or four months and no issues within the past year.
Also, make sure throttle cable tension is correct. Another thing to check is that the perch(s) that the throttle cable fits in aren't causing binding.
IIRC someone had a similar situation in the recent past, repalced the thermostat and it corrected the issue. However, I can't confirm this as I don't accuratley recall where I read it.
Also, make sure throttle cable tension is correct. Another thing to check is that the perch(s) that the throttle cable fits in aren't causing binding.
IIRC someone had a similar situation in the recent past, repalced the thermostat and it corrected the issue. However, I can't confirm this as I don't accuratley recall where I read it.
If that was the case, once I unplug IACV it should remain the same, but it doesnt. Also the fact that TPS reads dead on 0.5v, I doubt plate is open, even slightest otherwise voltmeter would pick it up from TPS... I'm just freaking lost to be honest, dont know where to look it makes no sense. No CELs either, unless I obviously disconnected IACV then I get it. Unsure how thermostat has anything to do with it though, ECU picks up temperature from ECT sensor?
12-29-2017, 05:41 PM
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12-29-2017, 06:04 PM
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Re: Idle stuck at 3,4k rpm.
Either idles is improperly set or you have a consistent vacuum leak.
Those would be my two guesses off the top of my head.
Those would be my two guesses off the top of my head.
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12-29-2017, 06:14 PM
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Re: Idle stuck at 3,4k rpm.
Also, remove IACV, clean it and the screen/gasket with brake cleaner. With the IACV removed test it with alligator clipjumpers to the battery and look and listen for clicking and movement within the solenoid. Wouldn't hurt to remove and clean the throttle body as well.
12-29-2017, 06:15 PM
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Re: Idle stuck at 3,4k rpm.
Everything worked fine so I doubt idle is screwed. Would vacuum leak make sense if car runs fine with IACV disconnected? Theoretically speaking, car would stall due to extra air, am I right or wrong here? Essentially yes but that's really vague from car to car. If it's running and I unplug it, it's going to stall, I have to keep revs for like 30 secs and then let go. I have OBD0 if that means anything ... But yes, idle drops.
12-29-2017, 09:21 PM
#10
Re: Idle stuck at 3,4k rpm.
More air usually means idle goes up as it adds more fuel to compensate for the added air.
ECU will try and keep the car at stoich level 14.7 for idle.
Unplugging the IACV I believe closes the air passage as I think it's spring loaded and motor controlled.
ECU will try and keep the car at stoich level 14.7 for idle.
Unplugging the IACV I believe closes the air passage as I think it's spring loaded and motor controlled.
12-30-2017, 04:21 AM
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Re: Idle stuck at 3,4k rpm.
But something doesnt make sense and I'd appreciate if someone can clarify on that matter. I believe it's not vacuum leak, and reason is simple, why would it lower rpms once IACV is unplugged? Vacuum leak should not affect IACV whatsoever, heck if there's indeed vacuum leak IACV would close to allow less air due to the fact engine is getting a lot more air than needed and it would compensate. Unplugging IACV DOES NOT restrict air in the engine, engines can run without IACV hence there's something more to it and I cant figure it out :/
12-30-2017, 04:25 AM
#12
Re: Idle stuck at 3,4k rpm.
Test ECT sensor with an ohmmeter. Even better, unplug the ECU and test the sensor and its wiring from the ECU end of the harness. A high resistance means the ECU thinks the engine is cold and will increase idle speed.
The two-wire IACV is a valve which is opened by electricity and closes itself by a spring when electricity is turned off. The circuit uses ground side drive like the fuel injectors. Thus having the IACV drive wire shorted to ground will pull IACV wide open.
In short, quit over-thinking and go out to the car and test some stuff.
The two-wire IACV is a valve which is opened by electricity and closes itself by a spring when electricity is turned off. The circuit uses ground side drive like the fuel injectors. Thus having the IACV drive wire shorted to ground will pull IACV wide open.
In short, quit over-thinking and go out to the car and test some stuff.
12-30-2017, 04:53 AM
#13
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Re: Idle stuck at 3,4k rpm.
Test ECT sensor with an ohmmeter. Even better, unplug the ECU and test the sensor and its wiring from the ECU end of the harness. A high resistance means the ECU thinks the engine is cold and will increase idle speed.
The two-wire IACV is a valve which is opened by electricity and closes itself by a spring when electricity is turned off. The circuit uses ground side drive like the fuel injectors. Thus having the IACV drive wire shorted to ground will pull IACV wide open.
In short, quit over-thinking and go out to the car and test some stuff.
The two-wire IACV is a valve which is opened by electricity and closes itself by a spring when electricity is turned off. The circuit uses ground side drive like the fuel injectors. Thus having the IACV drive wire shorted to ground will pull IACV wide open.
In short, quit over-thinking and go out to the car and test some stuff.
ECT is 2 months old ... Regardless, what resistance should I be looking for? Where do I locate the ground wire for IACV, bear in mind I'm OBD0, PM7 ECU.
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