Cold start problem on 1990 SX Corolla

**ozaristov300** · 08-08-2006, 07:59 AM

My daughter's Corolla (or specifically its 4AGE) has a problem on cold start. Normally the engine idles at about 1800-2000 RPM on a frosty morning and progressively drops back to normal idle as it warms up. Yesterday it developed this weird sort of possessed by demons things where it starts at 2000 revs but quickly builds to around 3000 RPM. After a minute or two it drops to 2200 then immediately back up to 2800 then straight back down to 2200 then immediately back up to 2800 (repeat sequence for all eternity).

Is there some exorcism process I can follow or alternatively a part I need to replace?

Thanx

**jonra23** · 08-08-2006, 08:50 AM

First guess would be a sticky idle speed control mechanism which bypasses air around throttle plate.
Pull air intake pipe off from thottle plate and give a good squirt with carby cleaner.

**kingmick** · 08-08-2006, 08:54 AM

Yep that or your throttlebody needs a good clean, does it stop once it is warm?

**richov8** · 08-08-2006, 08:55 AM

Sounds like the idle speed motor is out of range and the engine idle speed is hunting up and down due to the idle speed motor not being able to bring the idle speed down.
I would start with giving the throttle body a good claen with carby cleaner with and without the throttle plate open, give it a good blast and hold the accelerator flat when starting back up, to enable flood mode and give it a few revs, if still not better, reset ecu, (battery terminal off for a couple of minutes) and then see what it does.
From memory they have a wax pellet for idle speed??? Make sure there is not a air lock where the coolant hoses go into the bottom of the throttle body and the coolant level is good, see how you go.

**Talasas** · 08-08-2006, 11:53 AM

Sometimes air in the cooling system will do this on the 4AGE but the revs will flutuate between 2k - 3k every 2 seconds. If you get the air out of the cooling system and it still does it have a good look at the throttle body area (Aux. Air Valve and the like) there may be a restriction. If it takes ages to warm up the wax pellet mechanism is gone.

**ozaristov300** · 09-08-2006, 11:46 AM

Well the good news is the hunting problem was caused by a lack of hot water reaching the idle speed motor and was easily rectified by adding a liquid substance to the cooling system. Now the bad news: Where did the liquid, previously contained in the cooling system, migrate to? Stay tuned for more.

Thank you to Jonra23, Kingmick, richoV8 and Talasas for your knowledge and valuable assistance.

**ozaristov300** · 29-09-2006, 10:44 AM

For anybody interested, the leak turned out to be a cracked water pump housing. Eventually discovered a well-hidden, tell-tale brown streak on the face of the water pump.

**The Witzl** · 29-09-2006, 01:42 PM

Originally Posted by ozaristov300

For anybody interested, the leak turned out to be a cracked water pump housing. Eventually discovered a well-hidden, tell-tale brown streak on the face of the water pump.

I've seen this happen a few times.... it's not actually an "idle speed motor", it's an auxiliary air valve. Check out the 4A-GE Toyota service book if you can find one - its just a coolant temperature controlled air valve.

Hence the reason why air in the coolant causes it to operate funny