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Old 05-09-2009, 10:20 AM   #1
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Default Throttle sticking.

My brothers M45 miata has a problem with the throttle sticking.

You can give it gas and when you let off, it sticks where you let out. It isn't the cable.

1. Now here is the crazy thing. The TB is all the way closed like it should be.

2. Could it be The throttle position sensor??????

3. Could it be the AFPR is sticking, and causing to much gas to go into the motor?
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Old 05-09-2009, 05:24 PM   #2
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Could the AFM cause this?
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Old 05-10-2009, 01:45 AM   #3
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supercharger fail.jpg
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Old 05-10-2009, 04:48 PM   #4
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supercharger fail.jpg
Thanks for the help. LOL
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Old 05-11-2009, 12:47 PM   #5
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Originally Posted by Toddcod View Post
My brothers M45 miata has a problem with the throttle sticking.

You can give it gas and when you let off, it sticks where you let out. It isn't the cable.

1. Now here is the crazy thing. The TB is all the way closed like it should be.

2. Could it be The throttle position sensor??????

3. Could it be the AFPR is sticking, and causing to much gas to go into the motor?
I'm assuming "it sticks" means the rpm stays high.

1. You pulled off the plenum and laid eyes on the butterfly as you work the throttle? You say it's not the cable, and the specific design of the Miata TB escapes my brain ATM, but on some vehicles the return springs and linkage are such that it is possible for the cable to return like normal but the butterfly sticks open. Like if a separate return spring on the butterfly breaks or is disconnected, or if there's a ton of gunk up inside the TB so it doesn't close smoothly.

2. A stuck TPS won't keep the engine revving high (not very high anyway) if the butterfly is closed and the engine can't get enough air.

3. If you had a sticking AFPR and if the butterfly was actually closed, then the engine isn't getting enough air for the fuel being injected and will stumble and probably die rather than staying revved up.

It wouldn't be a bad AFM either.

What I'm saying is engines need air to rev. If it's staying revved up after you lift off the throttle, then it's still getting enough air to rev. There are other potential sources of air besides the TB butterfly (idle air valve, vacuum lines) but I don't think those would behave like a sticky throttle if they were the problem.
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Old 05-11-2009, 11:10 PM   #6
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Originally Posted by ScottFW View Post
I'm assuming "it sticks" means the rpm stays high.

1. You pulled off the plenum and laid eyes on the butterfly as you work the throttle? You say it's not the cable, and the specific design of the Miata TB escapes my brain ATM, but on some vehicles the return springs and linkage are such that it is possible for the cable to return like normal but the butterfly sticks open. Like if a separate return spring on the butterfly breaks or is disconnected, or if there's a ton of gunk up inside the TB so it doesn't close smoothly.

2. A stuck TPS won't keep the engine revving high (not very high anyway) if the butterfly is closed and the engine can't get enough air.

3. If you had a sticking AFPR and if the butterfly was actually closed, then the engine isn't getting enough air for the fuel being injected and will stumble and probably die rather than staying revved up.

It wouldn't be a bad AFM either.

What I'm saying is engines need air to rev. If it's staying revved up after you lift off the throttle, then it's still getting enough air to rev. There are other potential sources of air besides the TB butterfly (idle air valve, vacuum lines) but I don't think those would behave like a sticky throttle if they were the problem.
No joke man, I reached down by hand and the throttle was completely closed.

I'm just going to replace the whole thing.

Trackdog said a vac leak can do this sometimes.


I'm begining to wounder if the butterfly is broke like the other guy. It may bind enough to open it, but not get any grip to close it. I'm going to swap one on it. And another cable too. It may be a combination cluster of things. It is dangerous.
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