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Discussion Starter #1
Non-VVTi 1JZ-GTE here with 87,000 km's

Car starts up and fires perfectly fine, and no idling issues at all. Runs great except when I'm brake to a stop in neutral, to which I have to start it right back up again.

It doesn't happen all the time, but it is very annoying. Is this usually a dirty/clogged IACV that can cause this? Or the brake booster valve?
 

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Idle rpm? A/C on or off?
If the engine is loaded down with the A/C on the RPM will have a tendency do drop more when your foot comes off the gas in neutral.
Does the RPM change when you push in the clutch at idle?
You should also check the dashpot setting on the throttle body. It is used to prevent the engine from stalling when your foot comes off the gas by preventing the throttle plate from closing too fast so the engine has a chance to lean the rich mixture out.
You can check it by manually opening the throttle body and letting it go. If it snaps back closed then something is wrong with the dashpot. It should hit the dashpot and ease itself closed.
 

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Discussion Starter #3
Idle rpm? A/C on or off?
If the engine is loaded down with the A/C on the RPM will have a tendency do drop more when your foot comes off the gas in neutral.
Does the RPM change when you push in the clutch at idle?
You should also check the dashpot setting on the throttle body. It is used to prevent the engine from stalling when your foot comes off the gas by preventing the throttle plate from closing too fast so the engine has a chance to lean the rich mixture out.
You can check it by manually opening the throttle body and letting it go. If it snaps back closed then something is wrong with the dashpot. It should hit the dashpot and ease itself closed.
After warming up, it idles at 850-900rpm and remains steady. I haven't turned the A/C on since it's been cold in the past few days. The idle stays very steady and the RPM to my knowledge doesn't change at idle.

So you don't believe it's a dirty IACV that would be causing this? I'll check on the dashpot and see how that goes.
 

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You could take the IACV off and clean the little filter and you could probably test the stepper motor of the IACV with it off.
 

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Discussion Starter #5
You could take the IACV off and clean the little filter and you could probably test the stepper motor of the IACV with it off.
Okay, got it. I'll check the dashpot first as it's easiest to access and then I'll clean the IACV as well.

Are the dashpots rebuildable or do they need to be replaced as a whole?
 

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iSPOOL
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I would also check if your camshaft and crankshaft position sensors in good working condition along with IACV. I had a bad IACV and it cleared up my idling issue. I'm no mechanic but just using the old process of elimination you know.
 

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The dashpot has a diaphragm built in. If the piston doesn't slow it down then it might be blown.You can look here at the 7M-GTE page to check out the operation.
The 1JZ is not mounted the same but the operation is similar.
 

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Boost Junkie
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Does the car have a MAF sensor?

Steve
 

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Discussion Starter #10
I would also check if your camshaft and crankshaft position sensors in good working condition along with IACV. I had a bad IACV and it cleared up my idling issue. I'm no mechanic but just using the old process of elimination you know.
I don't have an idling issue; just the car randomly shutting off when I brake to a stop in neutral.
 

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iSPOOL
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I don't have an idling issue; just the car randomly shutting off when I brake to a stop in neutral.
Mine did as well when I let off the gas and stopped quickly sometimes. My idling issues were in addition. Just mentioned the sensors as well because in general they play a role in cars operation.
 

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Discussion Starter #12
Mine did as well when I let off the gas and stopped quickly sometimes. My idling issues were in addition. Just mentioned the sensors as well because in general they play a role in cars operation.
Got it, that makes sense.
 

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Boost Junkie
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Check for a vacuum leak. Under braking, the car will pull more vacuum and could possibly pull in un-metered air, which will cause it to run lean and then possibly cause it to hesitate or stall. My guess is that is your issue.

Steve
 

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Discussion Starter #16
What? non-VVTI is speed density (MAP). VVTI uses a MAF.
Oops, yeah it's a MAP sensor. I also have a VVTi-swapped X90 so I sometimes get the two mixed up. Thanks for the reminder, my bad!
 

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Discussion Starter #17
Update: I believe I may have solved the issue. On the intake manifold there was one nipple that was not capped which was most likely causing the intermittent stalling issues when slowing down/braking to a stop. Capped that port and so far it has not given me any issues since.
 
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