Bouncing Idle and no go during warm up

[AJz]

i know similar threads have been posted but all with slightly different problems. so here goes.

When starting my car it will idle high for a bit (this isnt the problem) then will drop down to about 700rpm and have a very rough idle, this will go between 500rpm and about 700rpm.

it will only does this for about 10 mins, and then its complely gone. before you suggest i have already replaced the plugs & leads, havnt replaced the dizzy or rotor tho.

Couple of people hav suggested air leaks, but then it should do the same thing once warm, so im thinking that cant be there problem, is there some sort of switch or bypass which switches on at cold to allow more air or sumthing, sorry noob Q but its driving me nuts.

And second thing, which probably links to first. When driving during this warm up period, car has no go unless you mash the pedal down, push it a quarter and it crawls away. But push it halfway and off it goes, im thinking this is linked with the first problem.

anybody got any ideas or had same problem?

(no mindless spam!!!, for once im trying to be productive and fix something

[EVL20V]

And second thing, which probably links to first. When driving during this warm up period, car has no go

ah, theres your problem, u have a celica

fix = get rid of it

[AJz]

shuddup fool, i want answers not spam

[l1ttle_d3vil]

sounds like it could be something similar to my problems, check out my thread 'won't idle when cold'.

in short, it could be a faulty auxilary bypass valve or something like that if your engine has got one.

[ollieboy]

My car was doing this the other day and it took me ages to figure it out but I think it was just moisture in the distributor cap. I wiped it out and it went fine again so I am guessing thats what it was. Mine did the same thing how when warmed up it was fine, it was strange how it didn't do it when warmed up though because you would think it would do it all the time if its wet dizzy. So you could try that.

[Crucible]

sounds like it could be something similar to my problems, check out my thread 'won't idle when cold'.

in short, it could be a faulty auxilary bypass valve or something like that if your engine has got one.

Does sound like the same problem, Check your coolant level as this will cause RPM fluctuation if low. When it comes up to op/temp you may be getting coolant over the valve when the thermostat allows flow , thats maybe why its fine when warm.

If the coolant level is fine, take the ducting off the throttle body when its playing up and block the holes before the throttle one by one, If the revs drop to normal the valve is either faulty or it is blocked with corrosion.

If there is no differance when blocking the ports then the problem is elsewhere. At the end of the day engine RPM will only increase dramatically if Air is bypassing the throttle wheather it be a faulty Air Valve, Stepper Motor etc or Unmetered Air ie - Vacuum leak.

Just my opinion - could be wrong!

TNT

[AJz]

cheers guys, thats some good advice. Something i didnt think about, will check tomorrow.

[AJz]

flushed and changed new coolant the other day, seems to be slightly better and now only seems to do it for a short time.

right, onto the idle control valve thingymedoobie.
below the throttle body is some sort of electronic unit/switch/sensor thing (does this control the air flow due to the temp of engine), then below that is a pipe which goes up underneath the throttle body.

This comes off the pipe which is connected between the throttle body and the filter box. now i hav accidently blocked this pipe b4 by not watching and it sucked up a dirty rag, which i managed to catch and pull back out, lol.

It basically almost stalled while doing this. Im guessing this is the pipe for the idle control valve? (at least i think thats wat its called)

Is this correct that the amount of air let through depends on the temp of the engine, more air so that it idles higher during start up so that the engine heats up to operating temp quicker.

Pics below.



The pipe behind the one for the idle control valve runs off the main piping from the radiator, the outlet for this is on the oposite side of the throttle body (first pic, the one going diagonally down) im not certain what the hose is that goes directly horizontal towards the firewall, i havnt looked where it ends up.

So yea, if anyone can confirm that most of what im saying is correct and yea, expand if you so desire. If the idle control valve is old/rooted. Are there just a single type, can they be simple cleaned out/fixed or do you need a new unit? cost?

hopefully this makes sense, second pic to help is below.



i think this all makes sense.....

sorta....

[AJz]

bumpity bump...

anybody help?

[jondee86]

Judging by what is written on the side of the valve (R/SISCV) what you
have is a Rotary Solenoid Idle Speed Control Valve. This modulates
the amount of air bypassing the throttle butterfly according to signals
supplied by the ICU. The ICU uses sensor inputs, including coolant
temperature, to determine the valve setting.

This valve is not normally used with a mechanical idleup valve (wax
thermostat type). The water hoses connected to the throttle body will
be to prevent throttle icing in cold climates.

An ECU controled idleup system would be unlikely to cause a loss of
power. It only controls the amount of air bypassing the throttle butterfly
which is no different than cracking the throttle open on a MAP sensored
engine. Maybe check your timing and your fuel pressure/fuel filter.

Cheers.... jondee86

[AJz]

ok cheers man.