SC400 Trouble
08-18-14, 11:31 PM
#31
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how low is it idling. it could be that it wasnt before and now its idling right. generally if it goes into closed loop and all the sensors are working it will want to idle around 650, which might sound too low but its not.
I agree with the reset and then drive it for a while. if it feels like its driving good again don't mess with the maf or you may have another issue to deal with. alot of times the IACV gets sticky in certain spots and it needs a complete teardown and relubing or just grab another one. spraying the shaft down with wd40 and working it left and right till its smooth again can help alot as well. if there is too much resistance it will stick in some position which sounds like whats happening now.
I agree with the reset and then drive it for a while. if it feels like its driving good again don't mess with the maf or you may have another issue to deal with. alot of times the IACV gets sticky in certain spots and it needs a complete teardown and relubing or just grab another one. spraying the shaft down with wd40 and working it left and right till its smooth again can help alot as well. if there is too much resistance it will stick in some position which sounds like whats happening now.
08-19-14, 09:19 AM
#32
If it was my car i would let it idle high and play with the pedal cable under the hood to see if its too tight. if that checked out i would get carb cleaner and spray for vacuum leaks.if that checked out i would check and maybe replace my coolant temperature sensor.if that doesnt work i would go to the TPS. hard to diagnose over the internet. but it sounds to me like the car is staying in open loop"cold start" and doesnt think its getting warm so idle stays high but it cant tell if the car is warm if the sensor isnt working properly
08-19-14, 10:02 AM
#33
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If it was my car i would let it idle high and play with the pedal cable under the hood to see if its too tight. if that checked out i would get carb cleaner and spray for vacuum leaks.if that checked out i would check and maybe replace my coolant temperature sensor.if that doesnt work i would go to the TPS. hard to diagnose over the internet. but it sounds to me like the car is staying in open loop"cold start" and doesnt think its getting warm so idle stays high but it cant tell if the car is warm if the sensor isnt working properly
I really appreciate the help, I will look for more vacuum leaks but I think they are covered. I just called autozone and the temp sensor is 17 bucks so I will probably go pick one of those up today as that should be a pretty easy fix to see if it works. The tps is pretty expensive so I'm trying to wait on that one until I'm certain. I have already adjusted the pedal cable and it seems to be ok. I will let you know how the violent sensor works out.
Many thanks again for the suggestions.
08-19-14, 01:15 PM
#34
if the maf was bad it wouldn't run well it would not just have a high idle.
if its not the iacv then the other things that make you idle high are a bad tps or not adjusted properly tps, or a vacuum leak, or the power steering idle up plastic vacuum switch thing has broken which you check by pulling the vac hoses and looking for power steering fluid in there.
I am thinking the tps then, they do go bad from time to time. if the tps is not in the correct position, the ecu will not tell the idle motor to idle down and go into closed loop = high idle.
If you want to do a quick test, mark the original position of the tps with a paint pen or marker, then try turning it while the engine is running. when you turn it from one side to the other fully, in one direction the engine will stumble and miss for a second, this is a sign of the idle curcuit in the tps working and the ecu getting confused why that triggers with not increase in rpm. If you get no change in engine sound when moving the tps around a bunch, you likely have a bad tps. if you do get the change in sound, tps is good and see if you can find a position where it will idle down to 650... there is like a 3-4 second delay after moving the tps. hopefully that makes some sense as a quick way to test if the ecu sees the tps. if all else fails and gets confusing move tps back to original position you marked.
if its not the iacv then the other things that make you idle high are a bad tps or not adjusted properly tps, or a vacuum leak, or the power steering idle up plastic vacuum switch thing has broken which you check by pulling the vac hoses and looking for power steering fluid in there.
I am thinking the tps then, they do go bad from time to time. if the tps is not in the correct position, the ecu will not tell the idle motor to idle down and go into closed loop = high idle.
If you want to do a quick test, mark the original position of the tps with a paint pen or marker, then try turning it while the engine is running. when you turn it from one side to the other fully, in one direction the engine will stumble and miss for a second, this is a sign of the idle curcuit in the tps working and the ecu getting confused why that triggers with not increase in rpm. If you get no change in engine sound when moving the tps around a bunch, you likely have a bad tps. if you do get the change in sound, tps is good and see if you can find a position where it will idle down to 650... there is like a 3-4 second delay after moving the tps. hopefully that makes some sense as a quick way to test if the ecu sees the tps. if all else fails and gets confusing move tps back to original position you marked.
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