Evo8 won't idle on cold start with new IAC
Feb 8, 2015, 12:57 PM
#1
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Evo8 won't idle on cold start with new IAC
****UPDATE: A connector on the ecu was not plugged in all the way. Don't know how that happened because I never touched it. ****
My 2003 Evo8(only mod is intake) won’t idle on cold start after I installed a brand new oem IAC and gasket. I tried resetting the ecu, but that did not work. I had to adjust the BISS to get it to idle. I warmed up the car, hooked up Evoscan and activated the Speed Adj. Screw mode. The idled dropped and I adjusted the screw to idle at 900rpm. I let it idle for 10 minutes before hitting "cancel." Was that the right button to click?
The car ran great and idled fine
However, I tried starting the car after it had cooled down(12 hours later) and it wouldn't start unless I pressed on the accelerator. Then it would only idle around 500 rpm on its own.
The car has no boost/vacuum leaks. The only CEL codes were for the high idle after I first adjusted it, and a random misfire
The IAC is the newer style valve that I believe came on the Evo9. From what I've read it should still work on an Evo8
I'm stumped on what could be causing it to not idle on cold starts, and any help is greatly appreciated.
My 2003 Evo8(only mod is intake) won’t idle on cold start after I installed a brand new oem IAC and gasket. I tried resetting the ecu, but that did not work. I had to adjust the BISS to get it to idle. I warmed up the car, hooked up Evoscan and activated the Speed Adj. Screw mode. The idled dropped and I adjusted the screw to idle at 900rpm. I let it idle for 10 minutes before hitting "cancel." Was that the right button to click?
The car ran great and idled fine
However, I tried starting the car after it had cooled down(12 hours later) and it wouldn't start unless I pressed on the accelerator. Then it would only idle around 500 rpm on its own.
The car has no boost/vacuum leaks. The only CEL codes were for the high idle after I first adjusted it, and a random misfire
The IAC is the newer style valve that I believe came on the Evo9. From what I've read it should still work on an Evo8
I'm stumped on what could be causing it to not idle on cold starts, and any help is greatly appreciated.
Last edited by Boombox; Mar 1, 2018 at 10:25 PM. Reason: problem solved
Feb 8, 2015, 09:47 PM
#2
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If I remember correctly , when I did this process a few months ago , I adjusted to 900'ish rpm with SAS being at on, for a minute or two , then i turned it off . The car wanted to stall for the first minute , but after it idled fine . I let the car idle for about 15 minutes . I think you do not have to idle so long with the SAS activated . Not sure if what you did could hurt the process .
Feb 10, 2015, 02:19 PM
#4
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Yes I did adjust the screw and calibrated the idle using Evoscan. However,blacktab420 may be right and maybe I let it idle to long while the Speed Adj. Screw mode was activated.
Could it possibly be my coolant temp sensor? I was reading that someone with a dsm had a similar problem where the car wouldn't idle when cold. His gauges and fans worked. Mine do too.
Could it possibly be my coolant temp sensor? I was reading that someone with a dsm had a similar problem where the car wouldn't idle when cold. His gauges and fans worked. Mine do too.
Nov 13, 2016, 02:25 PM
#5
Hey man, you updated the 1st post to say this was a wiring issue. Can you elaborate which wiring was at fault? Fuel pump wiring? I am having the exact same issue with my evo viii.
Feb 28, 2018, 07:47 AM
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Won’t idle on cold start
****UPDATE: It was a wiring issue****
My 2003 Evo8(only mod is intake) won’t idle on cold start after I installed a brand new oem IAC and gasket. I tried resetting the ecu, but that did not work. I had to adjust the BISS to get it to idle. I warmed up the car, hooked up Evoscan and activated the Speed Adj. Screw mode. The idled dropped and I adjusted the screw to idle at 900rpm. I let it idle for 10 minutes before hitting "cancel." Was that the right button to click?
The car ran great and idled fine
However, I tried starting the car after it had cooled down(12 hours later) and it wouldn't start unless I pressed on the accelerator. Then it would only idle around 500 rpm on its own.
The car has no boost/vacuum leaks. The only CEL codes were for the high idle after I first adjusted it, and a random misfire
The IAC is the newer style valve that I believe came on the Evo9. From what I've read it should still work on an Evo8
I'm stumped on what could be causing it to not idle on cold starts, and any help is greatly appreciated.
My 2003 Evo8(only mod is intake) won’t idle on cold start after I installed a brand new oem IAC and gasket. I tried resetting the ecu, but that did not work. I had to adjust the BISS to get it to idle. I warmed up the car, hooked up Evoscan and activated the Speed Adj. Screw mode. The idled dropped and I adjusted the screw to idle at 900rpm. I let it idle for 10 minutes before hitting "cancel." Was that the right button to click?
The car ran great and idled fine
However, I tried starting the car after it had cooled down(12 hours later) and it wouldn't start unless I pressed on the accelerator. Then it would only idle around 500 rpm on its own.
The car has no boost/vacuum leaks. The only CEL codes were for the high idle after I first adjusted it, and a random misfire
The IAC is the newer style valve that I believe came on the Evo9. From what I've read it should still work on an Evo8
I'm stumped on what could be causing it to not idle on cold starts, and any help is greatly appreciated.
What wiring issue was it? Having the EXACT same issue..
Mar 1, 2018, 10:44 PM
#7
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Thread Starter
One of my ecu connectors wasn't plugged in all the way. I just called it a wiring issue since that's what it technically was and I was embarrassed that I didn't check it. Sorry it was so vague. I had never unplugged the ecu before or even tried to access it, so I was surprised that one of the plugs wasn't in all the way. I was going to check for continuity in the wires but I noticed the plug wasn't in all the way. The car started right up and idled fine.
It it may be worth checking out on your car since the ecu isn't hard to get to.
https://shadetreespeedshop.com/my-car-is-hard-to-start-or-runs-poorly-cold-why/
^^i used this article while troubleshooting. Hopefully it can help you.
What really makes this issue so weird and stupid is that my car ran great when warm so there was no reason to think it was an ecu connector. The ecu connector with the IAC wires has the wires for the injectors and there wasn't anything wrong with my injectors.
It it may be worth checking out on your car since the ecu isn't hard to get to.
https://shadetreespeedshop.com/my-car-is-hard-to-start-or-runs-poorly-cold-why/
^^i used this article while troubleshooting. Hopefully it can help you.
What really makes this issue so weird and stupid is that my car ran great when warm so there was no reason to think it was an ecu connector. The ecu connector with the IAC wires has the wires for the injectors and there wasn't anything wrong with my injectors.
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