LQ4 Miata IAC getting stuck closed
02-23-2014, 07:54 PM
#1
Teching In
Thread Starter
iTrader: (1)
Join Date: Nov 2010
Location: Las Cruces
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
LQ4 Miata IAC getting stuck closed I have an LS swapped 1990 Mazda miata, i havent drove the car much just backing it out and back in the garage. Every once in a while it wont start or it will be idling and it will die. The IAC will fully close and wont allow any air in, if i pull off the sensor and push the pintel back to fully open, the car will start and run fine. I was wondering if any one know's what is causing it to fully extend and not retract. Thanks, Chase. I have also replaced it twice,so it is a brand new IAC valve
03-12-2014, 08:28 PM
#6
Teching In
Thread Starter
iTrader: (1)
Join Date: Nov 2010
Location: Las Cruces
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
today when i started the car it idled fine, then when i started it to move it back in the garage it idled fine and as i began to start pulling in it wanted to die so i gave it some throttle to keep it alive then it backfired one time and then died. It started up again like the iac stayed open. On my scan gauge it was reading 16ign timing and my wideband was between 12.6 and 13.0, does the timing sound right for idle or around 1500rpm?
03-12-2014, 09:49 PM
#7
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
IAC valve is a 4 wire stepper motor, its voltage is not
the deal - phase relation between two drive-pairs is
what moves it forward or back.
For the pintle to move like that, has to be either coming
from the PCM or some kind of crazy electrical spurious
action.
One thing to check in the tune is that IAC park position
is not "0". If it is then if the PCM thinks it's shutting off
it will try to drive it closed.
When it has this brain-fart, what does the scan tool say
is IAC Counts? If it thinks it's still open, when it's closed,
that's insanity that needs chasing; if it's going to zero by
intent and it knows it, then you have to figure out why
it wants no air.
Makes you homesick for an idle air bleed screw, doesn't it?
the deal - phase relation between two drive-pairs is
what moves it forward or back.
For the pintle to move like that, has to be either coming
from the PCM or some kind of crazy electrical spurious
action.
One thing to check in the tune is that IAC park position
is not "0". If it is then if the PCM thinks it's shutting off
it will try to drive it closed.
When it has this brain-fart, what does the scan tool say
is IAC Counts? If it thinks it's still open, when it's closed,
that's insanity that needs chasing; if it's going to zero by
intent and it knows it, then you have to figure out why
it wants no air.
Makes you homesick for an idle air bleed screw, doesn't it?
Trending Topics
03-13-2014, 11:18 AM
#8
Launching!
iTrader: (1)
Join Date: Nov 2004
Location: Jax, FL
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
Have you scanned the car with HP Scanner or something similar to see what IAC counts the PCM is demanding and what it is actually doing?
03-13-2014, 03:14 PM
#9
Teching In
Thread Starter
iTrader: (1)
Join Date: Nov 2010
Location: Las Cruces
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
No i havent, i had a friend with hp tuners but he got rid of it a couple months ago. Looking into getting one soon. I unplugged the iac and the car seems to run fine so far, just idling a little high because of the position of the pintel
03-13-2014, 04:53 PM
#10
03-13-2014, 11:43 PM
#11
Teching In
Thread Starter
iTrader: (1)
Join Date: Nov 2010
Location: Las Cruces
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
Today i left the IAC unplugged and drove the car to the gas station. After leaving on my way home all of a sudden it leaned out, my wide band was between 18-20. So i pull over and immediatly shut the car off. I call by bro n law to bring his scan tool, it didnt throw any codes that determine why it leaned out. So i started the car again and we were looking at the map and MAF tables, the map seemed to be reading correctly but the MAF was reading way low. It is a brand new maf, going to get a new one tomarrow and see what she does
03-15-2014, 02:16 AM
#12
On The Tree
iTrader: (2)
Join Date: Dec 2013
Location: Texas
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
IAC valve is a 4 wire stepper motor, its voltage is not
the deal - phase relation between two drive-pairs is
what moves it forward or back.
For the pintle to move like that, has to be either coming
from the PCM or some kind of crazy electrical spurious
action.
One thing to check in the tune is that IAC park position
is not "0". If it is then if the PCM thinks it's shutting off
it will try to drive it closed.
When it has this brain-fart, what does the scan tool say
is IAC Counts? If it thinks it's still open, when it's closed,
that's insanity that needs chasing; if it's going to zero by
intent and it knows it, then you have to figure out why
it wants no air.
Makes you homesick for an idle air bleed screw, doesn't it?
the deal - phase relation between two drive-pairs is
what moves it forward or back.
For the pintle to move like that, has to be either coming
from the PCM or some kind of crazy electrical spurious
action.
One thing to check in the tune is that IAC park position
is not "0". If it is then if the PCM thinks it's shutting off
it will try to drive it closed.
When it has this brain-fart, what does the scan tool say
is IAC Counts? If it thinks it's still open, when it's closed,
that's insanity that needs chasing; if it's going to zero by
intent and it knows it, then you have to figure out why
it wants no air.
Makes you homesick for an idle air bleed screw, doesn't it?
03-15-2014, 02:21 AM
#13
On The Tree
iTrader: (2)
Join Date: Dec 2013
Location: Texas
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
My IAC pintle doesnt move AT ALL and is stuck in the fully open position with the idle at 2000 rpm. I simply cannot find out what is going on....the harness checks out fine with all four wires (from the IAC) having continuity at the PCM connector. New IAC valve and TPS.
Care to add any input on this anyone??
Care to add any input on this anyone??
03-17-2014, 09:59 PM
#14
Teching In
Thread Starter
iTrader: (1)
Join Date: Nov 2010
Location: Las Cruces
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
I put my buddies MAF on my car so i knew it worked, car still leaned out after idleing in the garage for about a two minutes. Everything seems to be reading fine but as i was looking at the scan gauge the car stays in open loop, also the car will pull timing all the way back down to 7 degrees and causes it to backfire. Sounds like an issue in the tune like its locked in open loop, Anyone have anyother ideas?