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So I’m sure it isn’t the IAC. Took apart the IAC, throttle body, intake manifold, and fuel injectors for cleaning. Didn’t do it to solve the fuel trim issues, just as maintenance. Horrible mess inside the intake manifold. IAC is now cleaned out and seems to work fine, as far as I can tell. I think the only issue it could be is a vacuum leak now, but carb cleaner sprayed everywhere reveals nothing. I’ll find it eventually.
So I’m sure it isn’t the IAC. Took apart the IAC, throttle body, intake manifold, and fuel injectors for cleaning. Didn’t do it to solve the fuel trim issues, just as maintenance. Horrible mess inside the intake manifold. IAC is now cleaned out and seems to work fine, as far as I can tell. I think the only issue it could be is a vacuum leak now, but carb cleaner sprayed everywhere reveals nothing. I’ll find it eventually.
Installed a new PCV grommet. Didn’t help, but I didn’t expect it to. Needed a new one anyway, old one was torn up. Still can’t find the vacuum leak.
Replaced the TPS just in case with a spare I found, no change either. Still hunting. Planning a full clean of the TB and intake manifold for tomorrow.
Installed a new PCV grommet. Didn’t help, but I didn’t expect it to. Needed a new one anyway, old one was torn up. Still can’t find the vacuum leak.
Replaced the TPS just in case with a spare I found, no change either. Still hunting. Planning a full clean of the TB and intake manifold for tomorrow.
So I appear to be very wrong. The throttle opener depresses when the engine starts, keeping the throttle open at 10.6%. When the car is off, it pops up. So the throttle opener works fine. I sucked on the vacuum tube to it, it goes down by itself all the way just fine.
I read that some Toyotas have their throttles open at idle too. http://www.yotatech.com/f2/throttle-position-8-idle-normal-137497/
I took it to a shop and a mechanic just took a quick look. Both of us could hear a vacuum leak, but I still can’t find it. I think I’ll do a smoke test soon, blowing smoke into a vacuum line and seeing where it comes out. Because spraying brake cleaner is proving ineffective, as the leak might be in the EGR lines deep in the engine.
I also bought a new PCV grommet, just in case.
So I appear to be very wrong. The throttle opener depresses when the engine starts, keeping the throttle open at 10.6%. When the car is off, it pops up. So the throttle opener works fine. I sucked on the vacuum tube to it, it goes down by itself all the way just fine.
I read that some Toyotas have their throttles open at idle too. http://www.yotatech.com/f2/throttle-position-8-idle-normal-137497/
I took it to a shop and a mechanic just took a quick look. Both of us could hear a vacuum leak, but I still can’t find it. I think I’ll do a smoke test soon, blowing smoke into a vacuum line and seeing where it comes out. Because spraying brake cleaner is proving ineffective, as the leak might be in the EGR lines deep in the engine.
I also bought a new PCV grommet, just in case.
Unfortunately I don’t have a hand held vacuum pump. But I can say this. With the car off and the vacuum line undone, the plunger’s stock position is holding the throttle plate open. It feels like there is a spring inside, which holds it open but can be compressed when there is no vacuum, but pushes right back up.
Unfortunately I don’t have a hand held vacuum pump. But I can say this. With the car off and the vacuum line undone, the plunger’s stock position is holding the throttle plate open. It feels like there is a spring inside, which holds it open but can be compressed when there is no vacuum, but pushes right back up.
Are you sure? Take a look at this image:
The throttle opener is pushed up against the part that moves the throttle plate, and it’s keeping the throttle plate open at 10.6%. When the car is off, the throttle opener can be pushed in and the plate can be closed. With the car on, with vacuum, it cannot be closed.
Are you sure? Take a look at this image:
The throttle opener is pushed up against the part that moves the throttle plate, and it’s keeping the throttle plate open at 10.6%. When the car is off, the throttle opener can be pushed in and the plate can be closed. With the car on, with vacuum, it cannot be closed.
New development. The thing keeping the throttle body open is called the throttle opener (if I remember correctly), according to the sticker beneath the hood describing the EGR system. So I suspect the EGR system is at fault. I switched out the round EGR valve (circled in red) with one from a Camry (identical), and behavior didn’t change. The only other part of the EGR system it could be is the solenoid (circled in blue), right? Because the throttle opener is connected only by one hose to the EGR system, so I don’t see how anything else could keep the throttle body open. Any ideas?
New development. The thing keeping the throttle body open is called the throttle opener (if I remember correctly), according to the sticker beneath the hood describing the EGR system. So I suspect the EGR system is at fault. I switched out the round EGR valve (circled in red) with one from a Camry (identical), and behavior didn’t change. The only other part of the EGR system it could be is the solenoid (circled in blue), right? Because the throttle opener is connected only by one hose to the EGR system, so I don’t see how anything else could keep the throttle body open. Any ideas?
Yeah, I get as much as 18% higher in my short term. It’s abnormal. My O2 sensor is brand new, the 96 Corolla doesn’t have a MAF (uses an IAT sensor, which I confirmed works last night). No error codes from the ECU, so no problems it can find.
Cleaning of the TB, IAC, and intake manifold will happen this weekend.
I suspect it’s the TPS that’s become unadjusted and is pushing the TB open. But I can’t be sure.
Ninja edit: No hesitation problems either. Car is pretty speedy.