Weird Idle issue?

[modmonster2008]

I've been noticing lately, i would start up my car and typically it would idle at 1500RPM till about 5-6 mins it would drop down to 1100-100rpm, After driving around the heat finally is on full heat but when i come to a stop the idle would still be at 1000rpm's dead on. Then id go straight to work (25 miles) freeway usually and right when i get there i stop at the parking garage the rpm's would drop from 1000 down to 750 after that long of a drive, I know that somethings up with this because it wasnt like this before, can anybody point out some stuff i should look at? Let me know, thanks!

 

[hvyman]

Throttle linkage and tps right?

Isc working and clean?

Timing set right?

 

[modmonster2008]

Linkage does not seem like its having a pre-pull load on the throttle valve. TPS has never been messed with, nor is it throwing a code. ISCV and Cold start injector i will check, but when the car is shut off i hear some clicks like i'm supposed to hear. Timing is dead on 10* btdc with the two terminal things jumper to each other.

 

[hvyman]

Tps will not set a code when its off only if it bad sometimes.

Cold start will only effect starting not idleing.

Hows the throttle screw on the linkage like where you put thickness gauge to set the tps?

When you start should only go to like 1300 and after few seconds start coming down. The clicking sounds is 1 indication that part of it is good. But it also can be dirty. Also make sure that filter thing is in there and clean.

 

[modmonster2008]

I don't have the slightest idea of which screw you are talking about, the idle adjust-stopper screw? Or is it a different one? Ill remove the ISC valve tomorrow or something and take a look, theres a filter in there? It only looks like a valve and thats it..

 

[jrot]

mine does this too exactly...not that this is whats happening to you but the little spring under my linkage (under the pie shape that the cable rides on) is toast and only works if you snap right off the throttle from speed...if you let off slow it will drop to 1k then slowly drop to its proper rpm....when i first looked it seemed fine but after really looking close and moving it back and forth forever and really inspecting that is what i found....

 

[modmonster2008]

Ill check on that, but the thing is. If it were the spring, why is it only occuring to idle at 1000-1100 rpm's upon first startup of the day, after the car's been driven for more than 15 minutes or so the idle is at 750 throughout the entire day.

 

[jrot]

that i cant answer....i just know thats exactly what mine does...mine from time to time will settle in increments from 1k to 650ish but not often....but mine the little pie shaped piece i was talking about kinda slides back and forth making it impossible for me to adjust...and it moves such a small amount...when i get more cash and time im just gonna replace the whole thing and see if that and a fresh tps adjustment will solve it...no rush for me as it really doesnt happen much and it really doesnt bother me...for you since its right at beginning of the day maybe a good lubing of that spring or a good cleaning of the whole thing could work...also you might check too and make sure you dont have a some gunk built up near or on the butterfly in the throttle body...could be just that simple...maybe not....

 

[modmonster2008]

Alright thanks i will check up on those and maybe replace as well. By the way, I replaced my head gasket sometime in September. after the head gasket replacement was when this started to happen. and maybe once in a while (RARELY), when i start the car the idling would be around 500-ish and would fluctuate and seem like the car is going to stall, but when given gas for a little bit the car comes alive, could that be a sign of faulty ISC as well?

I am going to check the resistance measurements and clearances on the throttle/ISCV based on the TSRM, and i'll see what i can find out today.

 

[gottadiesel]

Alright thanks i will check up on those and maybe replace as well. By the way, I replaced my head gasket sometime in September. after the head gasket replacement was when this started to happen. and maybe once in a while (RARELY), when i start the car the idling would be around 500-ish and would fluctuate and seem like the car is going to stall, but when given gas for a little bit the car comes alive, could that be a sign of faulty ISC as well?

I am going to check the resistance measurements and clearances on the throttle/ISCV based on the TSRM, and i'll see what i can find out today.

Two thoughts come to mind:

In regards to the ISCV valve, it is best to do the full test per the TRSM, in which you induce voltage in one sequence to open and opposite sequence to close, it is a stepper motor... If dirty it can get hung up and not be moving to it's next step when the ECU induces the voltage.

2nd in mentioning the head gasket replacement - You need to make 100% sure that you have all of the air out of the coolant system, this can contribute to in-correct idling also, there is a section in the coolant chapter in TRSM on burping the coolant system.

 

[modmonster2008]

I'm sure the cooling system is properly bled, i added coolant and topped the car off, after a day raised the front up about 3' off the ground and opened the cap ran the motor till no air was coming out, after a while i checked my tee-adapter by the heater control valve the coolant was always topped off and no waterfall noise inside the cabin. I'll check on the ISC valve for proper functionality and dirt/debris buildup today

 

[modmonster2008]

Okay, so for the ISCV the TSRM says it should have resistance readings between 10-30 ohms, it read 21.9-22.0 ohms. The cold start injector had 3.3 ohms (tsrm says 2-4 ohm) So the resistance readings were okay. I dont know exactly how to test the iscv but i applied + voltage on b1 and b2 (middle terminals) and simultaneously grounded all the outer ones (s1,s2,s3,s4) kept doing that and i don't know but it seems the iac only moves a little bit it does not move a lot, it pretty much looks like it stays in one spot unless you look at it closely. Has anybody tested out the ISC valve?

 

[gottadiesel]

Okay, so for the ISCV the TSRM says it should have resistance readings between 10-30 ohms, it read 21.9-22.0 ohms. The cold start injector had 3.3 ohms (tsrm says 2-4 ohm) So the resistance readings were okay. I dont know exactly how to test the iscv but i applied + voltage on b1 and b2 (middle terminals) and simultaneously grounded all the outer ones (s1,s2,s3,s4) kept doing that and i don't know but it seems the iac only moves a little bit it does not move a lot, it pretty much looks like it stays in one spot unless you look at it closely. Has anybody tested out the ISC valve?

Yes I tested mine last summer during my start-up. I am not sure if I am understanding what you have said above, but you do not ground S1-S4 simultaneously, it is to be done in a sequence.

So while voltage is applies to B1 and B2, you go in a sequence starting with S1, then remove ground and go to S2, then S3, then S4, then back to S1... keep doing this until it is fully closed, then do the reverse sequence to test that it will fully open... S4, S3, S2, S1, S4 and so on... it moves a small fraction each time... seemed like it took 15-20 cycles to go one direction... but you should hear is click during each sequence step...

Hope that helps...

 

[hvyman]

Again. Cold start injector is only for starting NOT idle.

 

[modmonster2008]

LOL, i did mean in sequence, it didnt seem to be moving much i kept doing s1, s2, s3, s4 for about 10 times then did it the opposite way, it barely looks like its moving.

edit: i only heard slight clicks when i grounded the s1 and s4 terminals, it didnt seem to click when i grounded s2 and s3..

 

[gottadiesel]

Sounds like it (ISCV) is working to some degree, I do not remember if it only clicks at end/beginning of sequence or on each step... a couple of options, clean it and see if it helps.. 2nd not sure how often you make it towards the south or how quickly you want to resolve it... I have an extra ISCV, that you could borrow to test, if it is bad, look for one for sale... I really do not want to let mine go... but at least you could test before you buy one... I do go through that area 2-3 times per month working up at the Navy Base. Let me know or PM me and we can chat about getting it to you...

 

[shipkiller]

how air in the coolant system would affect idle?

 

[modmonster2008]

^gottadiesel, its alright i have my hands on one already, just gotta make sure this one works as well.

shipkiller: there is a sensor (ECU temp or cold start inj. switch) on the thermostat housing and i believe that if it does not read the right water level it would have a high idle, try starting your car in the morning without any coolant, the idle stays high up around 1500-1700rpm and doesnt really drop down, due to the switch.

 

[gottadiesel]

how air in the coolant system would affect idle?

In addition to what modmonster2008 said, if there is a small amount air in the system, often the rest of the coolant system may act normal, but the bypass lines and smaller lines may have a bubble in them... So if there is not continuous coolant running through the ISCV, so that the coolant temp running through the ISCV housing is not consistent with the rest of the coolant in the system, it will affect it's ability to work correctly, thereby having too high / too low or erratic idle...

 

[Suitcase Jefferson]

After about 5 minutes of warming up, my Supra idles at around the 700 - 800rpm range. I never put two thoughts to it.