Random Idle Issues 92 SC400
#1
Lexus Champion
Thread Starter
Random Idle Issues 92 SC400
I've been messing with this idle issue for months now. Basically short story is sometimes it idles great, sometimes it barely stays alive and idles awful.
-i have tested TPS and swapped the first TB TPS with the second one and they both work and measure degrees fine according to my Toyofan diagnostics tool.
-I have tested for vacuum leaks and eliminated a lot of vacuum lines anyways because EGR delete and power steering vacuum lines and so on. only vacuum lines left are brand new going to brake booster, PCV, FPRs, and charcoal canister (whatever the thing on the passenger corner is
-Alternator is a brand new Denso, charges perfectly
-ECU is rebuilt
-Entire ignition system is brand new (besides igniters on the fender, but they're tested working)
-Fuel pump ECU bypassed
-IACV is spotless, i took it completely apart and cleaned it (unplugging it changes nothing though, could it be bad, which pins do i use to test it for motor operation)
other than idle the car drives great, tons of power, no hesitation, no misfire, absolutely perfect, just the idle is weird sometimes and it seems to be completely random.
only code the car has is 13 which i've tested both cam sensors to be in spec and i've replaced the wiring on both cam sensors because they were chewed up, so maybe the timing has skipped a tooth but at this point idc cz the car runs great.
if anyone has the silver bullet for this i'd really appreciate it because i'm completely out of ideas at this point.
-i have tested TPS and swapped the first TB TPS with the second one and they both work and measure degrees fine according to my Toyofan diagnostics tool.
-I have tested for vacuum leaks and eliminated a lot of vacuum lines anyways because EGR delete and power steering vacuum lines and so on. only vacuum lines left are brand new going to brake booster, PCV, FPRs, and charcoal canister (whatever the thing on the passenger corner is
-Alternator is a brand new Denso, charges perfectly
-ECU is rebuilt
-Entire ignition system is brand new (besides igniters on the fender, but they're tested working)
-Fuel pump ECU bypassed
-IACV is spotless, i took it completely apart and cleaned it (unplugging it changes nothing though, could it be bad, which pins do i use to test it for motor operation)
other than idle the car drives great, tons of power, no hesitation, no misfire, absolutely perfect, just the idle is weird sometimes and it seems to be completely random.
only code the car has is 13 which i've tested both cam sensors to be in spec and i've replaced the wiring on both cam sensors because they were chewed up, so maybe the timing has skipped a tooth but at this point idc cz the car runs great.
if anyone has the silver bullet for this i'd really appreciate it because i'm completely out of ideas at this point.
#3
Lexus Champion
Thread Starter
i don't think that's my problem because when i unplug either, the car either completely stalls or starts doing even weirder stuff like RPMs going up and down all over the place.
#4
Lexus Champion
Thread Starter
tried starting the car yesterday and it wouldn't stay idling at all without gas, almost like the IACV is completley closed and no air getting to the engine at all. i'm gonna try to open the IACV manually and just leave it unplugged and see what happens. maybe even actuate it manually with the pins. i honestly think at this point that the IACV is the only issue because besides cold start idles the car runs fine.
#5
Lead Lap
iTrader: (2)
This is a shot in the dark but it may help. My 95 SC300 developed a battery draw that would kill the battery in a week or so if I didn't drive the car. When I jumped it it would sputter and cough and just run horribly until I got the battery fully charged and then it was fine. After a ton of searching I found out I had a corroded body ground. I want to say it's on the passenger side up by the radiator support or the front side of the wheel well hump. After I cleaned it up my issues went away.
#6
Lexus Champion
Thread Starter
This is a shot in the dark but it may help. My 95 SC300 developed a battery draw that would kill the battery in a week or so if I didn't drive the car. When I jumped it it would sputter and cough and just run horribly until I got the battery fully charged and then it was fine. After a ton of searching I found out I had a corroded body ground. I want to say it's on the passenger side up by the radiator support or the front side of the wheel well hump. After I cleaned it up my issues went away.
#7
Lead Lap
iTrader: (8)
Sounds like IACV to me. I would look for a used one to throw on and see if that changes the behavior. If you can get the connector along with it, that may be worth having in case yours is bad. Those connectors seem very prone to cracking, and gravity isn't their friend when it comes to staying in place.
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#8
Lexus Champion
Thread Starter
Sounds like IACV to me. I would look for a used one to throw on and see if that changes the behavior. If you can get the connector along with it, that may be worth having in case yours is bad. Those connectors seem very prone to cracking, and gravity isn't their friend when it comes to staying in place.
#10
Lexus Champion
Thread Starter
#12
Lexus Champion
Thread Starter
there's a youtube video on how to rebuild the IACV, very helpful
https://www.youtube.com/watch?v=cT7T...index=4&t=365s
https://www.youtube.com/watch?v=cT7T...index=4&t=365s
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