whats causing my high idle?
05-02-2011, 09:00 PM
#1
whats causing my high idle? quick background: bought a green 95z to donate its lower mileage motor and t56 to the car in my sig. only mechanical issue it had was a high idle. it would idle around 2k and sometimes drop to 1500 rpm
swapped motors and trans into the car in my sig, and it still has a high idle. i have reset and replaced the IAC valve and checked all vacuum lines on the motor by capping them off at the intake to absolutely no avail. after my "tweaking" it now idles at 2k rpm's until i touch the throttle, then it will stick at around 23-2500 rpm's. it idles high enough that in lower gears it will cruise without the throttle at a steady mph
like i said, i have reset the IAC twice, replaced it once, and checked all vacuum lines (other than the PCV and brake booster) and nothing has changed other than the idle getting higher. could it still be the IAC or could it possibly be the TPS? i will clean the IAC passages shortly to try to rule that out
swapped motors and trans into the car in my sig, and it still has a high idle. i have reset and replaced the IAC valve and checked all vacuum lines on the motor by capping them off at the intake to absolutely no avail. after my "tweaking" it now idles at 2k rpm's until i touch the throttle, then it will stick at around 23-2500 rpm's. it idles high enough that in lower gears it will cruise without the throttle at a steady mph
like i said, i have reset the IAC twice, replaced it once, and checked all vacuum lines (other than the PCV and brake booster) and nothing has changed other than the idle getting higher. could it still be the IAC or could it possibly be the TPS? i will clean the IAC passages shortly to try to rule that out
05-03-2011, 07:25 AM
#2
When my MAF signal wire got an open in it, it acted that same way; i.e. - 2K idle which would drop to 1300 or so when warm - I fixed the open, cleared the PCM - problem solved.
05-03-2011, 08:52 AM
#3
https://ls1tech.com/forums/lt1-lt4-m...-idle-iac.html
See my post at the bottom.
For the short version, this screams vacuum leak. If you hit the throttle, does it take a long time to come back down to where it began (RPM)? I suspect intake gasket leak or since you didn't check brake booster or PCV I would start there.
See my post at the bottom.
For the short version, this screams vacuum leak. If you hit the throttle, does it take a long time to come back down to where it began (RPM)? I suspect intake gasket leak or since you didn't check brake booster or PCV I would start there.
05-03-2011, 09:07 AM
#4
RPM's seem to stick now. Before I messed with it yesterday, they would hang around 2000 as long as the car was rolling, even in neutral, then drop to about 1500 rpm when it came to a near stop
I ended up getting under the car to address the issue of my fans not coming on, and happened to notice my belt has cut completely through one of my otvc wires. I need to decide if I want to replace all of them (less than 1000 miles on them) or just the one. I've never known a plug wire to cause a high, especially that high, idle issue. But maybe I'll get lucky
I ended up getting under the car to address the issue of my fans not coming on, and happened to notice my belt has cut completely through one of my otvc wires. I need to decide if I want to replace all of them (less than 1000 miles on them) or just the one. I've never known a plug wire to cause a high, especially that high, idle issue. But maybe I'll get lucky
05-03-2011, 09:44 AM
#7
Must be the high idle that has made the miss hard to notice. I will replace the plug wires and probably the TPS next the rule them out. A scanner that can read a 95 around here is near impossible to find, so until I get an ALDL cable it will be mostly guess work
