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Supra Dupra
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Discussion Starter #1
Sometimes my car idles kind-of weird. At times it would idle anywhere from 1000-1500rpm, but will slowly drop down to normal around 600-900 after I come to a complete stop. Doesn't happen all the time though. Another thing is, sometimes when I start up the car, it'll fire up and stay at idle (800rpm or so) for like 2 seconds and then kill itself. Car is at normal operating temp. When this happens, usually I keep my foot on the gas and rev it a little once or twice and it will be normal again.

I've heard that ISC goes out and is a common problem. Would this be the case for my senerio??? Is there any way I can test/fix it??? At cold start, everything seems to be fine. It just happens after I drive around for awhile and the problem starts. Any ideas???? :(
 

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Supra Dupra
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534 Posts
Discussion Starter #2
OH....I didn't find any boost leaks or vacumm leaks. The car is completely stock. Help guys??? :(
 
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Guest
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First check your computer codes. Follow the instructions exactly!

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_023.html

The ISC isn't know for failing often, but it can get dirty so it's response is slow and erratic. Clean it with carburetor cleaner, by spraying it into it's air hose with the engine running.

If you're more adventurous, take it off, and clean the pintle with carburetor cleaner and q-tips.

But usually this is all caused by a faulty TPS (throttle position sensor). They have a nasty habit of failing after 15+ years. :)
 

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Destroyer of Turbos
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i had the same praw... check your cold start injector.. mine was messed up so i cleaned it and fixed it no praw
 

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The Beginning
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1,146 Posts
If I remember you can tell if you ISC is working right if you turn the car off and right when engine shuts off you can hear a air suck noise followed by a clicking. That is the ISC, and suppose to mean it is good.
 

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the clever guy
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782 Posts
If I remember you can tell if you ISC is working right if you turn the car off and right when engine shuts off you can hear a air suck noise followed by a clicking. That is the ISC, and suppose to mean it is good.
So that's what that noise is....lol.

I had an ISC valve go awry and after the car was warm, it would usually die when I went into neutral approaching a stop. The idle would also oscillate from ~700 rpm to ~1700 rpm. I swapped it out with a spare I had, problem gone. Cleaning it is an option too, as mentioned above.
 

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Supra Dupra
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534 Posts
Discussion Starter #7
Shawndude said:
First check your computer codes. Follow the instructions exactly!

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_023.html

The ISC isn't know for failing often, but it can get dirty so it's response is slow and erratic. Clean it with carburetor cleaner, by spraying it into it's air hose with the engine running.

If you're more adventurous, take it off, and clean the pintle with carburetor cleaner and q-tips.

But usually this is all caused by a faulty TPS (throttle position sensor). They have a nasty habit of failing after 15+ years. :)
I don't have any computer codes. The check engine light hasn't turned on (knock on wood). :D Ummm.....it only does it when the engine is hot (normal operating temp.) I don't believe it would be the cold start injector then. But you think it could be the TPS????? :rolleyes:
 
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Did you check the computer codes? Many codes do not turn on the check engine light, only the more serious ones.
 

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Supra Dupra
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534 Posts
Discussion Starter #9
I'll follow the TSRM instructions to check the code(s). It says I need "SST" to connect to the terminals....is that just like a jumper wire????
 

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Supra Dupra
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534 Posts
Discussion Starter #11
Ok, I checked for codes and I got code 24 and 31.

24 - Air Intake Temp. Sensor Signal
31 - Air Flow meter Signal

What should I do/look for??? Wiring???.....???:(
 

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Supra Dupra
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534 Posts
Discussion Starter #12
You think its a bad AFM or perhaps it dirty????
 

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Supra Dupra
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Discussion Starter #14
yea, i'm gonna double check all the hoses and what not. I doubt I have a leak though. Pretty much all those hoses under the hood are new. I'll run a check on everything.
 
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I would very carefully check the wiring first. Take off the AFM connector and clean the pins, look for any broken or frayed wires. Also inspect the Oxygen Sensor wires, as this seems to be related.

Put it back together, and clear your computer codes by pulling the EFI fuse for about 30 seconds.

Bridge the T1-E1 connector and turn on the ignition key. See if there are any codes displayed. Start the car, and observe the check engine light, see if it throws a code. If still no code, it is a good sign.

With the engine running, wiggle the wires leading to the AFM, oxygen sensor and anything else you can get at (like the crank position sensor). Look for the engine to stumble or run rough or in anyway change while doing this. If it stumbles, check the codes and if it throws out the AFM code, you'll need to fix the wires you wiggled.

But whatever you do, DO NOT CLEAN THE AFM with anything. It will almost surely ruin it.
 

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Supra Dupra
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Discussion Starter #16
Hmmm....I checked all the wiring, connectors, everything seems to be in order. Haven't taken apart the intake though (AFM, air filter, filter box, accordian hose, & etc.), but all clamps are tight. O2 wires are good as are the AFM wires. Cleared the codes, driven 150 miles, everything is clear. However, the problem still exists.

I guess, I'll have to check the connectors with the engine running to see if anything happens.... :-(

Ergh....the thing is, it doesn't happen all the time, it only happens every so often. Cold start is fine, just happens after running the car for awhile, park the car, come back like 30 minutes to an hour later, and the problem occurs. When I fire the car back up again and keep my foot on the gas to prevent it from killing itself, the engine would stumble, shake for around 5-10 seconds before I can let off the gas and it will stablize itself. Ummm, could it be the O2, TPS, or CAS???
 
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91Supratium said:
Ergh....the thing is, it doesn't happen all the time, it only happens every so often. Cold start is fine, just happens after running the car for awhile, park the car, come back like 30 minutes to an hour later, and the problem occurs. When I fire the car back up again and keep my foot on the gas to prevent it from killing itself, the engine would stumble, shake for around 5-10 seconds before I can let off the gas and it will stablize itself. Ummm, could it be the O2, TPS, or CAS???
Is that the real problem? Because that is heat soak in the fuel rail, and I think every one of our Supras does it to one degree or another.

Check the Fuel pressure up system, as this is in there to directly help deal with the situation.

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_116.html
 
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I have a similiar problem, but it's the HKS Racing Bypass Valve and my lightweight FW.

BTW, I noticed you live in Concord, me too. What color is your car? I have a white 89T.
 

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Supra Dupra
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534 Posts
Discussion Starter #19
Shawndude said:
Is that the real problem? Because that is heat soak in the fuel rail, and I think every one of our Supras does it to one degree or another.

Check the Fuel pressure up system, as this is in there to directly help deal with the situation.

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_116.html
Ergh...I'm really lost at this point. Where is this VSV located?? I've heard of the heat soak problem, but my car is all stock and I don't drive hard, shouldn't it be fine??? Besides, it's like 45-50 degrees outside right now and the two fans don't even turn on.
 

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Supra Dupra
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Discussion Starter #20
Painless_1 said:
I have a similiar problem, but it's the HKS Racing Bypass Valve and my lightweight FW.

BTW, I noticed you live in Concord, me too. What color is your car? I have a white 89T.
I have a blue 91 turbo.
 
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