No Idle Issue
12-27-16, 12:41 AM
#1
Driver School Candidate
Thread Starter
Join Date: Dec 2016
Location: California
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
No Idle Issue
Hey folks,
Since I first had my sc400 I would have trouble with cold-starts. I would have to give it throttle to start the engine.
Progressively I would have to hold idle by pressing the throttle for as long as a minute or the engine would just stall.
However now I can not get my car to hold an idle under any circumstance. I have no check engine light. After many different sources led me to believe it was an iacv issue I ordered a replacement.
Unfortunately, replacing the iacv did not seem to fix the issue. The valve opens and closes freely by hand and is clean of carbon deposits.
I install the iacv as open as possible and the engine starts and idles (albeit high, but to be expected with an open iacv). For a few minutes everything seems to work fine but as the engine progressively warms
the iacv closes, to the point of being completely closed. I have heard of ECU's closing iacvs to learn it's respective range, but the iacv will stay completely closed. Is it normal for an iacv to close completely at any point?
Once the car is warm to a certain degree it will not idle whatsoever without throttle applied, even after cooling down and attempting to start. The iacv is completely closed once removed.
Why won't this damn thing open under cold conditions? Do i need a new computer? I feel like just leaving it partially open and unplugging it from the ecu. Is there a sensor related to the operation of the iacv I could fix?
Any help would be greatly appreciated.
Since I first had my sc400 I would have trouble with cold-starts. I would have to give it throttle to start the engine.
Progressively I would have to hold idle by pressing the throttle for as long as a minute or the engine would just stall.
However now I can not get my car to hold an idle under any circumstance. I have no check engine light. After many different sources led me to believe it was an iacv issue I ordered a replacement.
Unfortunately, replacing the iacv did not seem to fix the issue. The valve opens and closes freely by hand and is clean of carbon deposits.
I install the iacv as open as possible and the engine starts and idles (albeit high, but to be expected with an open iacv). For a few minutes everything seems to work fine but as the engine progressively warms
the iacv closes, to the point of being completely closed. I have heard of ECU's closing iacvs to learn it's respective range, but the iacv will stay completely closed. Is it normal for an iacv to close completely at any point?
Once the car is warm to a certain degree it will not idle whatsoever without throttle applied, even after cooling down and attempting to start. The iacv is completely closed once removed.
Why won't this damn thing open under cold conditions? Do i need a new computer? I feel like just leaving it partially open and unplugging it from the ecu. Is there a sensor related to the operation of the iacv I could fix?
Any help would be greatly appreciated.
Last edited by axisarm; 12-27-16 at 12:47 AM.
12-27-16, 02:48 AM
#2
Driver School Candidate
Thread Starter
Join Date: Dec 2016
Location: California
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
I remember plugging in a loose connector while replacing an idler pulley immediately before the no idle issue began. I think that connector was the connector to the iacv
I set the IACV to a position where it idles at about 900 in park and disconnected the harness at the sensor. Car idled but I could hardly tell if there was any difference to idle caused by increasing temp or power steering usage.
I'm going to attempt to bring the idle down to spec and see if it will start up with no throttle applied and hold idle under any load. Perhaps an idle of about 650 in drive with A/C on.
I have to adjust this by removing the iacv and carefully rotating the motor to adjust the plunger
I set the IACV to a position where it idles at about 900 in park and disconnected the harness at the sensor. Car idled but I could hardly tell if there was any difference to idle caused by increasing temp or power steering usage.
I'm going to attempt to bring the idle down to spec and see if it will start up with no throttle applied and hold idle under any load. Perhaps an idle of about 650 in drive with A/C on.
I have to adjust this by removing the iacv and carefully rotating the motor to adjust the plunger
12-27-16, 08:57 AM
#3
Glad you have "no idle issue." 
Have you replaced vacuum hoses? If not, that would be a simple and cheap place to start.
Was that loose IAC connector unplugged or just not plugged in firmly? Those connectors don't hold up well over the years and a loose fitting one that doesn't clip in properly can cause some problems. You can de-pin them and replace the broken old connector without splicing wires.
Have you replaced vacuum hoses? If not, that would be a simple and cheap place to start.
Was that loose IAC connector unplugged or just not plugged in firmly? Those connectors don't hold up well over the years and a loose fitting one that doesn't clip in properly can cause some problems. You can de-pin them and replace the broken old connector without splicing wires.
Thread
Thread Starter
Forum
Replies
Last Post
