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high idle caused by bad thermostat?

high idle caused by bad thermostat?

lex2oos
Member
138
20-02-2020, 10:12 AM
#1
While ago I cleaned my throttle body and did ecu reset, and after that my idle never went lower than 1k rpm at some exact frequency where engine shakes whole car...
So few days ago I took it off again and changed gaskets to prevent any vacuum leaks that could cause high idle.
first test was a success - cold engine around 1.5k rpm and when warm idle fell down to smooth 650-700 rpm.

I think my car has bad thermostat, because when driving engine never heats up as high as it should, close, but not enough.

Today cold engine did idle close to 2k rpm, driving around it warmed up as much as it could but idle never went lower than 1.1k rpm.

Is there still a vacuum leak somewhere or engine just keeps rpm's high to warm up?
Another strange thing I noticed - when driving when I put in neutural rpms fall down to 1k and bounce back to 1.5k and falls again and bounces back again, when speed gets lower this bouncing stops and stays at idle (around 1.1k rpm)

This is my engine temp after ~30min drive round town with 1 degree celsius outside
[Image: DSC_6181.jpg]

first possible solution, I guess is thermostat change....
any other options?

what causes this bouncing when coasting in neutural?

Car is year 2000 manual, all stock 1g-fe

thanks for reading
lex2oos
20-02-2020, 10:12 AM #1

While ago I cleaned my throttle body and did ecu reset, and after that my idle never went lower than 1k rpm at some exact frequency where engine shakes whole car...
So few days ago I took it off again and changed gaskets to prevent any vacuum leaks that could cause high idle.
first test was a success - cold engine around 1.5k rpm and when warm idle fell down to smooth 650-700 rpm.

I think my car has bad thermostat, because when driving engine never heats up as high as it should, close, but not enough.

Today cold engine did idle close to 2k rpm, driving around it warmed up as much as it could but idle never went lower than 1.1k rpm.

Is there still a vacuum leak somewhere or engine just keeps rpm's high to warm up?
Another strange thing I noticed - when driving when I put in neutural rpms fall down to 1k and bounce back to 1.5k and falls again and bounces back again, when speed gets lower this bouncing stops and stays at idle (around 1.1k rpm)

This is my engine temp after ~30min drive round town with 1 degree celsius outside
[Image: DSC_6181.jpg]

first possible solution, I guess is thermostat change....
any other options?

what causes this bouncing when coasting in neutural?

Car is year 2000 manual, all stock 1g-fe

thanks for reading

mattlaw
Senior Member
572
20-02-2020, 10:28 AM
#2
I've had is200 running and idling funny when the wiring to the temp sensor in the bottom of the rad has broken off, I'd be checking there first
mattlaw
20-02-2020, 10:28 AM #2

I've had is200 running and idling funny when the wiring to the temp sensor in the bottom of the rad has broken off, I'd be checking there first

lex2oos
Member
138
21-02-2020, 09:21 AM
#3
I think bottom of the radiator is fan switch not temp sensor, but Ill check...
Today was a warm sunny day and when engine heated up when standing, idle was normal, afted driving, engine temp went down and idle up... so its thermostat
lex2oos
21-02-2020, 09:21 AM #3

I think bottom of the radiator is fan switch not temp sensor, but Ill check...
Today was a warm sunny day and when engine heated up when standing, idle was normal, afted driving, engine temp went down and idle up... so its thermostat

SHAHZ
Posting Freak
2,142
22-02-2020, 03:31 AM
#4
Mines doing the same at the moment, I'm doing an hour each way to work at 80 and it don't get up to temp... Must be the temp sensor or thermostat .... If left idling for a while it gets warm enough to let the rpm drop to normal

Tinted Glass-Sports Grill-Debadged-TTE Spoiler-TTE Lowering Springs-PLUK Kazama Exhaust-18" Aero Alloys-K&N Air Filter-Denso Iridium Power Spark Plugs-Quad Tail Light Conversion-6000K HID-X-White High Beam-6 LED Sidelights-Quad LED Boot Light-JDM OEM Smoked Front Fogs-JDM Blue Reverse Bulbs-LS430 Smoked Side Repeaters-6 LED Side Repeaters-Chrome Indicator Bulbs-Alpine HU-Rear Headrest Monitors-PIAA Super Sporza-Fan Washer Jets-Lex Tax Disc Holder-Chrome Gear Knob-2003 Cup Holder-Toyo Proxes T1-R
SHAHZ
22-02-2020, 03:31 AM #4

Mines doing the same at the moment, I'm doing an hour each way to work at 80 and it don't get up to temp... Must be the temp sensor or thermostat .... If left idling for a while it gets warm enough to let the rpm drop to normal


Tinted Glass-Sports Grill-Debadged-TTE Spoiler-TTE Lowering Springs-PLUK Kazama Exhaust-18" Aero Alloys-K&N Air Filter-Denso Iridium Power Spark Plugs-Quad Tail Light Conversion-6000K HID-X-White High Beam-6 LED Sidelights-Quad LED Boot Light-JDM OEM Smoked Front Fogs-JDM Blue Reverse Bulbs-LS430 Smoked Side Repeaters-6 LED Side Repeaters-Chrome Indicator Bulbs-Alpine HU-Rear Headrest Monitors-PIAA Super Sporza-Fan Washer Jets-Lex Tax Disc Holder-Chrome Gear Knob-2003 Cup Holder-Toyo Proxes T1-R

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