clok

iTrader: (2)

So I have a rebuilt 3vze with 6k miles on it with just about 90 percent new parts on it (injectors, egr system, throttle body, vacuum lines ,knock sensor and just about everything you can replace on it u have , the motor runs super good and strong , only thing that bothers me is when I start it up cold it idles at about 1300k rpm for about 4-6 min. Before it drops to its proper 850-900k rpm. , or I have to drive it for a few miles before the idle drops to the proper idle , my question is why does it take 4-6 min for the idle to drop to its proper idle (850)rpm ? I replaced the exhaust temp sensor ,02 sensor and every other sensor even the fuel pulsation , fuel regulator,new throttle body tps sensor etc. the only thing I have not replaced is the water coolant sending unit could this be the key to my problem.?

rworegon

Is the engine getting to full operating temperature and then the idle continues to run high? The idle will not typically drop until the ECU sees the coolant temp is in the normal operating range which depends on engine load, ambient temperature, etc.

The Engine Coolant Temperature (ECT) sensor that talks to the ECU may have a mineral scale layer on the probe that causes wonky data for the ECU. Pull the ECT and if scale is present carefully wire brush it off.

Is the thermostat in good shape and of the proper temp?

jennygirl

I agree- I would think it's thermostat related. There is an air valve built into the bottom of the TB that is actuated to be open when the coolant flowing through it is cold, closed when hot for normal idle. It is there to help warm up the engine faster.

This is a feature most engines have. If the idle is excessively high, then you either have a bunk thermostat or maybe there is an air pocket in the coolant system (preventing flow through there which keeps the cold idle up air valve open longer / wider than it should be).

I would pop the thermostat and check it out to see if there is corrosion on it. Then I would properly "burp" the coolant system through the radiator cap. I just explained how to do that here. Air in the coolant system can cause all sorts of funky stuff speaking from my own personal experience!

Good luck

clok

iTrader: (2)

thermostat is new its the 180 degree versus the stock 195 degree , and where is the ECT located? Pictures ? Once the engine gets to full operating temp the idle drops

clok

iTrader: (2)

thank you I will try and burp the coolant system

rworegon

I'm not sure exactly where the ECT is located on the 3vze. The location is at the back of the engine and the placement of the sensor in the line up changed over the years IIRC.

Idle drop at operating temp is what it's suppose to do. I'm not really sure there is a issue with your idle.

jgrant721

I have a '91 4Runner 3VZE that I have owned since new. Everything is pretty much stock. The behavior you are questioning seems like perfectly normal operation in my experience. My truck will idle high for several minutes (1200 rpm) while the engine/coolant is heating up, before gradually dropping down to the normal 850 rpm. The time it takes depends on the ambient temperature; longer in winter, shorter in summer.

Just my two cents worth!

Jim G.

clok

iTrader: (2)

maybe your right it is getting colder over here now , still gonna replace the coolant temp sensor to the ecu tomorrow I'll update if it did anything.

DavidLovesToyotas

Had a 3vze for 2 years now, and i can tell ya high idle on cold start up is normal. Ive seen up to 2000rpms for cold idle on below freezing days.

clok

iTrader: (2)

ok cool thanks , I timed my idle today in the afternoon at 70 degrees it took 10 min. To reach proper idle , then again at night in 60 degrees it took 10 min. Again to reach proper idle , I think 10 min. Is a bit to long , gonna replace the sensors.

clok

iTrader: (2)

Anyone know what the engine coolant temperature switch located towards the back of the intake manifold do ? , I have a new engine coolant sensor , and a new engine coolant temperature sender for the gauge , and a new cold start inj. Time switch , but couldn't get my hands on a engine coolant temperature switch have to order it. Trying to replace all the sensors located behind the motor today.

clok

iTrader: (2)

Well replaced three out four sensors and idle already well behaving , only sensor I couldn't replace was engine coolant temperature switch , but old sensors I pulled out where and looked like oem 24 yrs old and shot.