How IAC/ISC works?
10-21-05, 04:56 PM
#1
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How IAC/ISC works?
Let's say, when engin is cold, the volve is open or closed?
then, when the engine is at normal temp, is it open or closed?
When we plug in a jump wire between E1 and TE1, the volve supposes to
open or closed?
I read from some resurces on how to check the IAC:
At normal temp, when plug in the jump wire, engine speed will
increase and keep at 1000 rmp for like 5 seconds ( or 10 sec?)
then it will go back to normal. Anybody could tell me why is this?
Does this mean the volve will be open or closed for a while and
then it will go to the status before putting in the jumper wire even
with the jump wire still pluged in?
then, when the engine is at normal temp, is it open or closed?
When we plug in a jump wire between E1 and TE1, the volve supposes to
open or closed?
I read from some resurces on how to check the IAC:
At normal temp, when plug in the jump wire, engine speed will
increase and keep at 1000 rmp for like 5 seconds ( or 10 sec?)
then it will go back to normal. Anybody could tell me why is this?
Does this mean the volve will be open or closed for a while and
then it will go to the status before putting in the jumper wire even
with the jump wire still pluged in?
10-21-05, 06:13 PM
#2
No, no no no no no no no no no no no...
You need to wipe the slate clean. Forget everything you just said because it's just a bunch of random things thrown around.
To test an IAC/ISC the resistance of the valve should be:
3vz-fe is 10-30ohm
1mz-fe is 17-28.5ohm
If you suspect the idle valve to be having problems, clean it out as they're normally just clogged with carbon.
Use whatever carb/throttlebody cleaner you like & scrub the inside with a small brush.
Also clean the EGR valve, and throttle plate.
I have found the Tri-Flow is a great lubricant after you finish cleaning.
You need to wipe the slate clean. Forget everything you just said because it's just a bunch of random things thrown around.
To test an IAC/ISC the resistance of the valve should be:
3vz-fe is 10-30ohm
1mz-fe is 17-28.5ohm
If you suspect the idle valve to be having problems, clean it out as they're normally just clogged with carbon.
Use whatever carb/throttlebody cleaner you like & scrub the inside with a small brush.
Also clean the EGR valve, and throttle plate.
I have found the Tri-Flow is a great lubricant after you finish cleaning.
10-21-05, 06:22 PM
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Not sure what all you are saying there, or why. But I do know that when it idles high the is OPEN more.
Originally Posted by allerton
Let's say, when engin is cold, the volve is open or closed?
then, when the engine is at normal temp, is it open or closed?
When we plug in a jump wire between E1 and TE1, the volve supposes to
open or closed?
I read from some resurces on how to check the IAC:
At normal temp, when plug in the jump wire, engine speed will
increase and keep at 1000 rmp for like 5 seconds ( or 10 sec?)
then it will go back to normal. Anybody could tell me why is this?
Does this mean the volve will be open or closed for a while and
then it will go to the status before putting in the jumper wire even
with the jump wire still pluged in?
then, when the engine is at normal temp, is it open or closed?
When we plug in a jump wire between E1 and TE1, the volve supposes to
open or closed?
I read from some resurces on how to check the IAC:
At normal temp, when plug in the jump wire, engine speed will
increase and keep at 1000 rmp for like 5 seconds ( or 10 sec?)
then it will go back to normal. Anybody could tell me why is this?
Does this mean the volve will be open or closed for a while and
then it will go to the status before putting in the jumper wire even
with the jump wire still pluged in?
10-21-05, 06:34 PM
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OK, the reason I'm suspecting the IAC is that the car stalled this morning
when it had a cold starting. I have to step on the gas to keep it from dying.
After driving a while, the idle speed went normal.
So it seems to be a cold idle problem. I'm still not sure if it is the IAC.
Since the idle works fine when temp is normal, I'm tryiig to figure out
how the IAC works in either cold or warm cases.
when it had a cold starting. I have to step on the gas to keep it from dying.
After driving a while, the idle speed went normal.
So it seems to be a cold idle problem. I'm still not sure if it is the IAC.
Since the idle works fine when temp is normal, I'm tryiig to figure out
how the IAC works in either cold or warm cases.
10-21-05, 06:47 PM
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Hmmm, clean the throttle plates and intake, you can also remove the ISC and clean it. Be careful though, don't use much cleaner on the intake and plates, better to spray it on a rag and wipe it clean. Don't pray a bunch of cleaner into the intake, you'll damage the engine. You CAN pray the ISC alot, so long it's removed.
An easy way to test the ISC...idle the car, turn the A/C on, and the ISC should compensate for the A/C compressor "drag". If the engine idles down alot then yes, you have an ISC or electrical problem.
An easy way to test the ISC...idle the car, turn the A/C on, and the ISC should compensate for the A/C compressor "drag". If the engine idles down alot then yes, you have an ISC or electrical problem.
10-21-05, 06:51 PM
#6
The IAC works the same in all conditions. The TCCU opens it based on the amount of airflow hat the engine needs to run when the throttle plate is closed, or near closed. It doesn't have a set pattern you can watch, it runs live.
All you can do is either check it's resistance, clean it, or replace it.
You're at the right starting point. Test the IAC & clean it (or just clean it). If the problem doesn't go away & the idle & EGR valves TOK, move on to other common problems.
All you can do is either check it's resistance, clean it, or replace it.
You're at the right starting point. Test the IAC & clean it (or just clean it). If the problem doesn't go away & the idle & EGR valves TOK, move on to other common problems.
10-21-05, 06:54 PM
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Good. it is easy to turn on AC and see what happens.
Is there any other mechanism which takes care of the idle
when the engine is cold?
Anyway, I'll find a good day to clean those carbons...
Is there any other mechanism which takes care of the idle
when the engine is cold?
Anyway, I'll find a good day to clean those carbons...
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