Intermittent 4AGE stalling/ bad idle problem

[RobertoX]

As the title states, I have a probelem with my 4age (bigport) stalling, usually when the throttle closes and the revs drop from about 4000 upwards.
Its a real annoyance when I stop at the lights and the engine stalls, even more so when I have a starter solenoid that overheats.... that's another issue though.

Anyway, the idle will also drop and fall regularly intermittently, sort of oscillating between 900 and 1200rpm (period of about 2 seconds). Other times it'll be ok.
Besides all this the engine has reasonable torque.


So far I've fixed an oil leak in the distributor, replaced the old plugs and leads and changed the timing belt. which may have been related but didn't fix anything.

Anyway, any ideas of what to do? Are there any common problems with bigports doing this?

Thanks

[pandaah]

sounds like you may have abit of a vacuum leak maybe, id be trying to spray around the intake with throttle body cleaner and see if the motor revs up

[Duk]

Worn rotor button and distributor cap can cause similar fun.

Dirty/stuck idle speed control solenoid.

Cam timing is definitely correct when you are looking at timing marks front on (not on an angle)?

[LeeRoy]

Got a pod filter?

[RobertoX]

Thanks guys,

No pod filter (factory airbox with higher flow panel)

Solenoid - high possibility, I've been getting some oil blowby and it may have clogged the air bypass
Cam & ignition timing are correct.
Replaced the Distributor cap with no change and rotor button is in good nick.
I checked for air leaks with a bit of hose to the ear but will try the carby cleaner.

Cheers

[jazae86]

Hi,

Wax hot idle control vavle under the throttle body. buy new gasket & oring before you dismantle as you will destroy the gasket in removal. It is easier to remove throttle body off the intake (also get this gasket). Clean the throttle body totally and clean the cold idle control section, removing all the bits of silicon and crap that has entered over the years.

This may help with part numbers, but then again being in Japan, Toyota may actually be helpful there: http://www.toyodiy.com/parts/p_J_198...CMQF_2211.html

[oldeskewltoy]

Hi,

Wax hot idle control vavle under the throttle body. buy new gasket & oring before you dismantle as you will destroy the gasket in removal. It is easier to remove throttle body off the intake (also get this gasket). Clean the throttle body totally and clean the cold idle control section, removing all the bits of silicon and crap that has entered over the years.

This may help with part numbers, but then again being in Japan, Toyota may actually be helpful there: http://www.toyodiy.com/parts/p_J_198...CMQF_2211.html

thumbs up on this...


I'd also add a few things... check your VSV, sometimes called idle up valves. Used for PS, A/C, and high load alt draws

[RobertoX]

Looks like I'll have something to do saturday morning... thanks for the advice on the parts, I'll order some gaskets and stuff.
That Toyodiy site is awesome, I even manage to use it for work sometimes

For the VSV, it seems to be working fine.
I've actually removed the aircon belt for another reason and when I switch the aircon on, the engine idles up. So I'm using it as a quick fix at the moment.

[predator]

You have actually adjusted the idle screw to raise the idle??

[RobertoX]

yeah I did that too...

[ae92gtapex]

Mine did a similar thing. I replaced the oxygen sensor and was good as gold.. They have a life of around 100,000k's before needing replacement. Also make sure there is no air in the cooling system as the wax pallet is a nice little place for it to hide.

Good luck with it

Cheers
Gaz

[ollie83]

Fuel filter or failing coil?? Coil is easy to check using a multimeter and checking the resitance of the primary and secondary coils. There are a few guides on how to do this (google it). Fuel filter is relatively cheap to replace so may be worth just putting a new one in for peace of mind, and seeing how it goes. I'd check the coil though first.

[RobertoX]

Thanks!
I've got a new fuel filter, the old one was really old looking so I replaced recently.

Coil I will check.
Oxygen sensor, I can borrow a good one to see if it fixes the problem. I always thought a 4age should run without one, you just get a bit less economy when running closed loop?

I pulled the throttle off and took off the valve, but haven't had a chance to put it all back together again yet.
So while it's off, is there a method to check it's operation?
Should I lubricate it or anything?

[Chrisso]

Grab a thermometer and a pot of water. You will need to connect some hosing to the valve so that you can blow through it when it's submerged. I just jambed some rubber hosing in. Put it in the pot, onto the stove and heat it up. Once you get to ~82*C the valve should close and you won't be able to blow through it.

Mine failed this test miserably and I just put an aluminium plate in instead to block it off.

[RobertoX]

So still experiencing the same problem.

I checked the cold idle valve - works fine (closes completely with hot water)
Replaced the gaskets / o-ring

Replaced motor with fresh built long block (in relation to a separate problem!)

Coil is OK

What next?
I had a thought that fouled injectors could cause it to overfuel at idle thus making it stall. However, someone mentioned that this would also make it hard to start which it isn't.
Anyway, is this worth looking into.


Anything else? I'm out of ideas...