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Discussion Starter · #1 ·
87 mk3 Supra turbo 5 speed.
Recently purchased this car with my son and have been going over a few things on the car. Car would start but wouldn’t idle unless you gave it throttle. Son decided to pull the ISC Valve to see if it was dirty or damaged.
Upon inspection the tip of the plunger seemed a little odd. Almost looks like someone put a bead of weld on the end. Hoping to get some people to offer opinions on if this is normal or not.
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I'm pretty sure it's not normal. The tip should maintain an even shape all the way around.
That build-up around the tip looks similar to the hard carbon deposits and sooty material on my IACV. To remove it, I had soaked it in penetrating oil and using some steel wool and dull knife to scrape off the deposits. Very carefully did it as to not gouge or mark the original metal.
 

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Nice pictures of the ISC with deposits. Good find. This is behind a lot of rough idle/stalling with these engines. I have usually seen dry powdery deposits choking off the air bypass passage ways. Seldom see the ISC itself go bad. This is a clean up and reinstall for sure.
 

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Discussion Starter · #4 ·
I had a chance to start cleaning this valve. It was definitely not carbon deposits. For some reason it appears that someone welded a little dob onto the end. I hope I didn’t mess it up but I filed the weld down to a uniform shape trying to match the other side. Hopefully it works once I get it put back together.
 

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It was definitely not carbon deposits. For some reason it appears that someone welded a little dob onto the end. I hope I didn’t mess it up but I filed the weld down to a uniform shape trying to match the other side. Hopefully it works once I get it put back together.
Really odd why someone would weld the tip. But yeah, hopefully there is an improvement.
Here's what my IACV looks like after I had cleaned the tip.

And BTW, I didn't read in your post but do you have a check valve and rubber spacer that goes between IACV and intake manifold?
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Please response if this grinded tip (to nearly original shape) will work.
For me looks like you need a new ISC valve, but first I would give it a try too. When it works, then nice. If you still struggle, go and get another one ;-)
 

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Applying a weld bead to the tip sounds like a strange attempt to fix by a prior owner. I assumed it was some solidified carbon deposits. Why would anyone try to weld on the tip? Looks like you did a really good job reshaping it. Hope it works. Let us know how it turns out.
 

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Stock 1989 Supra Turbo w/ Sport Roof
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This inspired me to clean mine and I saw that mine has the same welded tip. I wonder if it was just a manufacturing artifact.
 

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Discussion Starter · #15 ·
When my son first removed the entire valve from the manifold he said that the rubber o-ring between the plunger assembly and the electrical assembly end was just hanging out of the case. The o-ring used by whoever worked on this before but in a o-ring that was way too big. We have been having a difficult time trying to source one. Any ideas? We have tried all the local auto parts stores with no luck.
 

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Stock 1989 Supra Turbo w/ Sport Roof
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When my son first removed the entire valve from the manifold he said that the rubber o-ring between the plunger assembly and the electrical assembly end was just hanging out of the case. The o-ring used by whoever worked on this before but in a o-ring that was way too big. We have been having a difficult time trying to source one. Any ideas? We have tried all the local auto parts stores with no luck.
I had the same issue. I ended up using RTV. Lol. I also ordered some gasket material for the IAC to manifold gasket.

@Whoosh10 my idle was a tad high. Just under 900 warmed up in neutral. I noticed my plunger piece was not all the way in contact with the seat as well. The tip doesn't seem to really matter aside from directing airflow from what I can tell.
 

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Discussion Starter · #17 ·
Checked the resistance and operation of the ISC valve tonight as noted in the service manual. Everything thing checked out. Resistance was within spec a valve was moving with power applied. Think I will just try some rtv sealer in lieu of the o-ring and get it installed. Hopefully it works out. Waiting for an alternator to come in first.
 

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Checked the resistance and operation of the ISC valve tonight as noted in the service manual. Everything thing checked out. Resistance was within spec a valve was moving with power applied. Think I will just try some rtv sealer in lieu of the o-ring and get it installed. Hopefully it works out. Waiting for an alternator to come in first.
Definitely use the RTV sparingly though. I got mine exactly in the groove with a tiny bit extra on top. Still smooshed out quite a bit. I was afraid it would seep towards the spring and jam everything up but it actuated correctly when I tested it after curing.
 

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That welded tip is normal. Mine has it too. The motor is a stepping motor which means it moves in and out incrementally depending on the sequence the coils are energized. Here is a reference in the online manual that demonstrates how to test. Click here to go there. Note the orientation of the check valve and rubber washer. It lets air in one direction.
 

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Discussion Starter · #20 ·
To hear that the welded tip is normal make me nervous that I have filed it down to smooth it out and may have damaged it and changed it from what was designed. I hope when we have everything ready to fired it up again it all works out.

I have performed the tests in the manual and could see and hear the plunger moving in and out. It definitely moves a very small amount with every sequence through the terminals.
 
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