Last straw HELP? or im going to ask satan. idle,

[Lordpaxin]

background:
1991 tsi awd JDM swap, aswell as MT swap.

everything works fine, engine will boost strong to 9-10 psi at 2200rpm
during throttle there is no hesitation or inconsistancys in rpm, or engine functions.

When you first start the engine. idle hangs around 2200 rpm and is rock steady.

once engine reaches temperature, idle begins to surge anywhre from 1000 - 2000 rpm.

while driving down the road, and you let off the throttle, engine will surge, buck kind of, like if you would be decellerating in gear, and tap the gas gently (indicating the surging)

my ISC is good, dunno about the PIAV, or whatever its called.

I know my base timing is slightly off, but it isimpossible to correct that, while my idle is gorilla cocked.

did a boost leak test, and i cannot find anything, NO check engine lights, no nothing, except sometimes, my coolant light (birdcage) will light up, and go off again.

making me think the temperatre sensor may be bad, and the engine doesnt know if it is warmed up or not, or the signal from the sensor is oscillating, and making the engine go in and out of warmup repeatedly.

any ideas. will be super cool.
also, on the thermostat, there is 2 places to plug in the small wire. one of front, and one or back. dunno if thre is any bearing.

thanks, adam, sorry for the longpost.

 

[Lordpaxin]

I just found this, would this be a reason it only surges at operational temperature? if so, what is the procedure to bleed air from coolant

"An air pocket in the coolant system may also cause an idle surge. On some vehicles, there is a coolant passage in the throttle body. The TB is frequently the highest point in the coolant system and an air pocket may form there. This air pocket may also cause an idle surge so make sure you've properly bled the air from the coolant system before addressing any idle concerns.
Doug"

 

[AwdEi]

Have you tried to bleed the system?

I was going to say, sounds like the FIAV (fast idle air valve) but backwards. Usually when the fiav is messing up, it will surge until warm. It is not hard to fix, either get another TB, or you can block off the fiav. Not a big free mod, but it keeps temps down in your intake b/c 200 degree coolant isn't running to the TB. Supposedly, it takes long to start in cold weather, but I haven't had any problems.

Hope this helps.

 

[Lordpaxin]

how do you get air out of coolant? i have no friggin clue about this, ill try anything.

why go through the trouble to block it off, and just get the two coolant lines and just connect them together

 

[Defiant]

Originally posted by Lordpaxin

did a boost leak test, and i cannot find anything, NO check engine lights, no nothing, except sometimes, my coolant light (birdcage) will light up, and go off again.

making me think the temperatre sensor may be bad, and the engine doesnt know if it is warmed up or not, or the signal from the sensor is oscillating, and making the engine go in and out of warmup repeatedly.

It's not that, the light's only for coolant level in the expansion tank. DSMs don't need to be "bled", the thermostat's high enough to get all the air out on its own.

Hit the throttle body with some WD-40 at idle, see if it gives you a spike around the throttle shaft seals.