More info, is your car fully stock, bpu, bpu++...., is it an auto or manual.

 

bpu and 6sp manual.

 

First place I would look is vac leaks. Then check the IAC

 

ECU caps make this problem also

 

Did anyone mess with the "idle adjustment" screws?

 

check your PVC valve while you're at it

 

+1. mine does this before when the PVC was shut. Replace it with new one solve the problem

 

Checked for vac leak using the carb spray method but might try smoke machine method instead.

 

How is the driving in cold start up. when give it a little throttle does it respond immediately or like a little miss then jump

 

Mine does this... any idea what would make it do that? (Sorry to get off topic)

 

cold start up is fine and good throttle response. engine doesn't have a miss. idle is around 800rpm when cold and later drops to below 500rpm when the engine is warm.

 

this is happens in old Camry as well. car idles low when get warm and stalls when coming to stop..... replacing IACV solve the problem.

furthermore 1jz guys face this problem when ecu capacitors start leaking, because there is a capacitor in IACV circuit.

 

ordered a cheap party smoke machine to help look for hidden vacuum leaks. I plan to clean the IAC valve instead of replacing. also ordered the engine and fuel pump fuel filters just to be sure. checking the simple stuff first before tackling the more complicated stuff. thanks for the tips.

 

Try soapy water too. Worked the best for me by far.

 

dumb question but wouldn't that suck in the soapy water into the leak in a vacuum line unless you pressurize the system?

 

Please keep us updated. I have the same issue with my car and I've gotten so annoyed with it that I almost don't miss driving it.

 

that's blasphemy!! haha.

 

Mine supra does the same thing. I was told it was either the spark plugs or coils. Upon further investigation I found a fault with the map sensor not working properly.

When under load around 4000rpm do you find the car sort of stutters/doesnt want to go as fast as it could/should?

 

the engine runs fine throughout the rpm range. no misfires or stuttering which makes me think it's not an ignition problem. I suspect a problem with airflow or fuel delivery problem. would a map sensor fault generate an error code?

 

I've got the same issue on my 98' Quicksilver car, on cold start it idles around 500rpm! Gonna try cleaning the IACV soon.....

 

my 2jzge will idle fine cold. then later itll drop to 500rpm. my plan of action is IAVC cleaning with TB cleaner, then ohm out ecu temp sensor.

 

Something worth checking is your throttle.body setup. Make sure the throttle opener is not leaking, that the tps is set up properly and that the throttle opener and dashpot are set correctly. Always best to have a proper baseline before you start indiscriminately swapping parts. The tsrm has procedures for this and if you have questions feel free to pm. Also check all vac hoses. The supra has some really hard to reach lines so be thorough.

 

Forgot to mention tps. Make sure that is set correctly as well.

 

ok this past weekend I replaced the engine fuel filter, cleaned the IAC valve and mass air flow sensor using specific cleaners made by CRC. did a short test drive and idle appears improved. we'll see in the long term. still waiting for my smoke machine to check for vacuum leaks in any of vacuum hoses. I'm considering replacing the in tank fuel filter and both O2 sensors.

 

today I replaced the fuel pump filter, front and rear O2 sensors. did the smoke test but couldn't find any vacuum leaks. so far the engine did not stall.

 

so far so good. idle is back to normal around 800 to 900rpm and more importantly no stalling. here is a summary of what I did to correct the idle problem. some of items might have been a waste of money and time but at least my idle issue is gone. added in items 10 & 11 that I forgot.

1) replaced engine fuel filter
2) replaced in tank fuel sock
3) cleaned IAC valve
4) checked for vacuum leaks using party smoke machine
5) replaced front and rear O2 sensors
6) replaced clutch switch (not the switch on the floor near the firewall)
7) replaced tell tale left light cluster. this cluster didnt work before with key "ON" therefore check engine light was not working so I wasn't sure if I had any error codes. now the cluster lights up with the key "ON" and confirmed no error codes.
8) cleaned throttle body
9) replaced coolant temp sensor near upper radiator hose
10) cleaned MAF sensor
11) cleaned EGR valve

 

#3 and #8 were the ones that probably helped, with an outside chance of #9 if it was bad.

Al

 

try adjusting the TPS. I got the idle to around 900rpm by turning very slightly counter clockwise.

 

As a quick fix you can always jack open the throttle body with a screw or adjustment bolt on some engines. You want to disable the IAC so it doesn't add any air; that way you can find the minimum idle first; then plug in the IAC and let it carry the last couple RPM. Do it fully warm.