Problems with Idle

[MatthewG]

Hi guys,

got some problems with my 86 non cat:

i pull out my engine and gearbox to refresh all oils and service stuff,Things i have done:

seal the oilpan,new engine oil,new gearoil,new sparkplugs (orig. Toyota Denso)
new airfilter (stock),new watercooler,new oil cooler!

than i put back engine and gearbox connect all hoses and plugs (several times checkt! and i got a second 86 to check it too) and.....

idle makes what it wants, up and down, from 1900 to 3500 rpm....
it is a better when i disconnect the throttle sensor,rpm stands now on 1500 but when i what to hold it at any higher rpm by hand its jumps again!!

so i change the sparkplugs to the old ones (ngk) ......a little bit better......
then change the throttle sensor (4 pieces).. still the same...than i change the ecu, still the same...then i change the fuel pressure regulator, still the same.....then i began to play with the ignition put it is still the same......

Can any one help me!!!!!
Thanks ,martin!

[Ivan141]

Loping idle can also be caused by problems in the cooling system... check if it's working properly and topped up enough.

[parrot]

I agree with Ivan141. Make extra sure you have properly bled all the air out of your cooling system (with the heater tap open). Also make sure you have connected up the two sensors on the rear of the head near the firewall (green and brown).

[jondee86]

As above, and in particular check that you get the air out of the
thermostatic idleup valve under the throttle body. Apparently if this
is air locked it can lead to erratic idle... I don't really know why

If bleeding air from the system doesn't solve the problem, I have
heard of many cases where cleaning and/or replacing the thermostatic
idle up valve has returned the idle to normal.

Cheers... jondee86

[MatthewG]

Thanks,

i think this might be the problem cause i bleed the air out of cooling system but didn´t bleed out of my heatingsystem!

will check this day!

martin

[MatthewG]

hi,
no this is not the problem!!!!!air is out of water cooling system!still the same probs with idle! any other idea!
thanks,martin

[oldskull]

I got this problem also. Mine cause one of the pipe from radiator to engine (or to t-vis i am not sure) was stopped. This is because of my car was 7 year stand still and the owner had water instead of cooling fluid in the radiator so the whole system is rusting and stopped. After found out the pipe was stopped and we change to another pipe and the timing going smooth again till today

[Ivan141]

Loping idle on 4age's in 9 out of 10 times a cooling system problem.. as oldskull just mentioned, a silly clogged up pipe to the throttle body bypass valve can cause grief. Never had problems with trapped air in the cooling system myself.
The TPS sensor (which you've already replaced) is the other regular culprit.

Also make sure you plugged the right connectors to the correct sensors...I once managed to cross the 2 ones on the rear of the cylinder head which caused all kinds of grief.

[MatthewG]

the two plug near the firewall are pluged in right and are not interchanged!!!

i almost forgot to tell u that i change the timingbelt, tensioner and water pump too, sorry guys!
timingbelt is also change on right way, checkt several times!

[robokill]

if you timing is set correctly (10btdc with the connector en 16btdc or more when its disconnected)

I have had the same problem with my car and still have actually. In my car one of my wires had some interferance. Therefore I was unable to locate the problem caus it didn't happen every day.

There are so many causes that if you done everything in the manual you can only start replacing the big stuff. For fun and check hang the engine into the other car