1994 Legacy with 97 GTB TT Hunting for idle, surges from 1500rpm to 2000rpm. new air flow meter installed

sounds like a vacuum leak, or possibly a Mass Air Flow issue.

By using a small piece of hose (heater hose). Check the induction manifold gasket for air induction. Use the hose like a listening tube along the length of the gasket area.

Hi there, i had a similar problem with my Legacy B4 RSK Blitzen, 2 litre Twin Turbo, Engine EJ208. Car would idle sort of ok when cold, after warming up it would idle erratically (idle hunting) and cut out sometimes. I notices the boost gauge hunting along with the RPM'S .I found it to be 2 faults. 1st fault - If you have an after market air filter and the car hasn't been mapped for the extra airflow past the MAF (Airflow Meter) then it confuses the ecu as its taking in un-metered air. Solution - Re-map car to take extra airflow or as i did, i took out the MAF and cleaned it with a can of Carb&Choke cleaner. It worked but still had rough idle.
2nd fault - Air could be in your cooling system. If there is air in the system then the engine temp sensor is reading hot/cold/hot/cold everytime an air bubble passes by, which will cause running problems. You may hear a gurgling or slushing noise in the car, which is air in the heater matrix. Solution - From cold open the header tank and coolant overflow bottle, un car untill engine warm and hold at 2000-4000 rpm untill you see air bubbles rise in the header tank. Make sure your hot air is turned on in the car and vents open. Do this process for 10-15 mins and when you think all air is out of system then re-fit header tank cap. Have a watering can at hand as you may require to top it up during bleeding. It will overflow but dont worry.


Only real problems Legacy's give are , Air Flow Meters, Knock sensors, and Lambda Sensors (O2 sensor). Hope this helps mate, keep us informed on how you get on.

Clean MAF Sensor

Check for vacuum leaks

Check Air Idle Control Solenoid,
if you have one

Clean throttle body plate

Hi.it sound a lot like a ignition coil coils tend to do that if its got a crack it Swell when the temperature rises

its gonna be your clutch i had the same problem, when i floor it the rpms would go high then drop and take off i replaced it and it runs fine know

sounds like you have a very dirty mass air flow meter. invest in a new one and be sure to clean the throttle body with an appropriate cleaner and tooth brush.

Try changing the air flow meter this sounds like yours is faulty.

Have you put the OBD scanner on it to find the problem. That would be a good place to start. the computer should have stored a code with the problem.

Since the problem obvasly was not solved, try replacing the fuel injectors, as most of the time this is what causes these symptoms.