The engin was running, cut out after 3min, give me code 18 and a tri angle

are you checking these while they are hot?

Corsa 1.4i
Engine code Z14XE 2000-2004 Bolts must be replaced after removal.
stage 1. 25Nm
stage 2, +90 degrees
stage 3. +90 degrees
stage 4. +90 degrees
stage 5. +45 degrees
Engine code C14NZ 1993-1998
Stage 1. 25Nm
stage 2. +60 degrees
stage 3. +60 degrees
stage 4. +60 degrees

LET YOU TECHNICIAN MEASURE THE GAP ON COMPRESSOR CLUTCH.IS COMMON IF THE GAP IS TO BIG COMPRESSOR ENGAGE LATE.AFTER 2-3min.
LOCATE THE SENSOR FOR CABIN TEMPERATURE AND MAKE SURE IS NOT DUSTY . LET THE DEALER PLUG THE SCANNER AND READ THE LIVE DATA BEFORE START THE CAR.BAD OR DISCONNECTED SENSOR WILL READ -40*F. SELECT LIVE DATA AND WILL SEE THE SIGNAL FRO THE BODY CONTROL MODULE TO A/C RELAY(ON / OFF)
ENGINE DATA IS IMPORTANT TO. A/C CUT OFF ON OVERLOAD FROM ENGINE,POWER STEERING,ETC
.

Do you know what you are loosing when the engine stops running ?

That is a common crankshaft angle sensor trait just before it quits completely. Find your crank angle sensor (almost behind the crankshaft pulley) and when your engine gets hot & cuts out, pour cold water over the sensor to cool it down. If the engine then starts straight away the sensor is faulty.

Is the check engine light on when the engine is running ? If it is, check for trouble codes.
My first guess would be a faulty throttle position sensor. The sensor tells the computer what the angle of the throttle plate is. The sensor tends to wear out just off idle where you keep your foot on the gas pedal the most.
Could be a vac leak or something else too.

The ECM gets it messages for heat from the engine coolant temperature sensor. The sensor is probably bad. Since the fans come on right away the ECM is in a safe mode for the engine. Meaning it turns the fans on because it can't read the coolant sensor. As far as the fans staying on for a couple of minutes this is normal when the engine is hot. The ECM does this.

Seems like the coolant temperature sensor is giving the computer erroneous readings, and it is not adjusting the fuel mixture properly for cold engine operations. You should have the check engine light on, indicating this malfunction. The idle fluctuations are normal. The engine is trying to die, from the improper cold mixture, and the computer (ECM), recognizing low idle speed, is sending it back up. Another possibilty is that the butterfly on the throttle body is not closing completely, to allow richer mixture needed for cold starts.

check or replace ignition module and coil if injected crank angle sensor

You have a TransMission Problem..It's Called a "Torque Converter Lock-up solenoid" ..

When the Engine is cool the solenoid is not being used,
When the Engine is Hot, the solenoid Kicks in and makes your Chevy Run like your pulling an 18 wheeler.

Wait till the Engine is Cool, Slide Under your Van, Drivers side near the shifter is a 4 wire Plug.
Un-plug the wire and see if your trans works after it's hot.. your just by-passing the solenoid BUT I have never found a use for it my self..

IF you still get Lock up after this, you are stuck bringing to a trans shop or see if the solenoid cam be removed without ripping the whole trans apart..