Changed the battery on my99 impreza, started it up and when warm the revs would hunt on idle, which i was told was down to the MAF sensor, bought a new one yesturday, reset the ECU with the connectors under the dash and run car. now the hunting on idle has gone and its running rough on idle when left ticking over for about 3 - 5 minutes, its as if its only running on 3 cylinders, as soon as i pick the revs up its perfect. I changed the plugs today because i thought this could be the fault but its still the same. I done a compression test just incase but that hit the correct readings, i also swapped the coil pack with one i have spare. checked the ECU for faults but is all clear, ive replaced vac pipes incase it was sucking air in but still no joy, now i just dont know where to look next as nothing has been disturbed apart from the battery, could it be a faulty MAF

Can anyone help as i was going to take the car for a remap next weekend but dont want to do it if there is a fault with the vehicle

 

Anyone??????

 

Does sound like the MAF.

 

Have you driven it much since the ECU reset?

 

Had a replacement maf today fitted it and run it for around 70 miles, still exactly the same. Going to have a good look over it tomorrow. Any ideas where start and what to check first ?

 

Replacement MAF or brand new?

Graham

 

brand new

 

update........just pulled a vac pipe off the manifold while engine was idling to check for any splits where i fitted them and found when the vac pipe was remove and the inlet manifold was sucking air in, the engine run sweet and idled perfect as soon as i reconnected vac pipe it started running like a sick pig again. I removed the air filter to see if maybe that was retricting air but made no difference. strange!!!!!!

 

Stripped manifold Off and found the rubber intake pipe that goes on to the turbo inlet has gone all soft and breaking up and sucked in, going to order a new pipe and see of this sorts it out.