misfire - hesitation - bad idle
 

ive had this problem for about a month now and very close to taking it to subaru for a diagnostic, but first wanted to check a few things it could of been so tried taking off maf with engine running and cuts out so not that, had a few weeks with crap 95 ron fuel (couldnt get my usual 99ron) so went back to 99ron and reset ecu but not that, been suggested its probably the lambda sensor so want to disconnect it to see if it looks black and clogged up but cant work out how to undo the plug and dont want to damage it, also today checked the ht leads all seem ok and took out all the plugs and was no damage but were quick black so must be running rich but my also tried to check the gap on the plugs before putting them back, what should the correct gap be? if gap is too small will it cause the engine to stall? as its struggling to stay ticking over now...

what year and model is your car

its an impreza turbo 2000 uk 97 facelift

Goujon

I'm having very similar problems on my 97 car. Although i have Apexi ECU rather than the Subaru one.

My lambda and MAF sensors seem to be working OK. My plugs were 0.8mm which is what Subaru workshop manaul says, changed them to 0.65 as recommended on Scoobynet, made the misfire a whole lot worse. Have changed them up to 0.9mm and I still have the problem but its less apparent.

My car is running really rich, plugs very sooty.

Currently I'm looking into the coolant temp sensor, my guage reads temperature fine and the Apexi controller shows a sensible water temp but I've seen something that says there are 2 temp sensors. Don't have this confirmed yet but the advice is if ECU thinks engine is cold it'll keep adding extra fuel, hence running rich and errativ problems.

I have added item in that I recently replaced plug leads with aftermarket ones that were a present, although now I've investigated they might be worse than old factory ones.

Apart from that I'm head scratching, have you got any further?

hello mate, i had i mobile diagnostic guy come to me as i wasnt able to drive it due to it being so bad it would of been dangerous to drive as kept wanting to stall and revs wouldnt hold much past 5000 plus the hesitation. anyway he checked the fuel pressure which was fine then connected it to the diagnostic tool which said no volts from lambda sensor and fault with maf also 4 stored faults of maf. so i got a new lambda sensor which did nothing, i did an ecu reset and checked the codes which showed 23 (maf) and 17 (4th injector) so got a 2nd hand maf and a set of injectors, i put the maf on and started it and it runs fine now so i did another ecu reset then checked the codes and its clear now so i didnt bother getting the injectors changed. its been 2 weeks since i did this and still seems to be running fine, i also fitted a bracket to the induction kit as i had it loose before which i think caused the maf failure with all the movement.

was it missing badly and have trouble starting

Induction kit on 99/00 is def a no no due to the chocolate MAF. I'm from WGC as well mate. I have a X reg Mica red scoob with gold wheels, may see you around ;)

hello mate, yeah might see you about only trouble is this morning i had a front end smash and did the bumper bonnet passenger headlight, foglight and indicator and bulb holder, luckily i had a spare old bonnet and bumper so theyre on but still need to replace the lights asap...

Oh dear hope you get it sorted, get yourself on flea bay quick ;)

yeah got most of it sorted today, got the spare bonnet and bumper on and cracked foglight and indicator just need to get the headlight off ebay now then ill get a new bonnet bumper foglight and indicator when i can afford it but itll do for now.

kevin wrx

it was running rough like it was misfiring and would start but would tick over so low after about 2 minutes it would cut out unles you kept the revs going to run it also if you tried to rev it up to full it would get to about 5500 - 6000 rpms then want to go back down again also hesitation low down revs but the replacement maf seems to of solved the problem i also put in a new subaru lambda sensor to which made no difference to the problem so it was the maf. i even checked the ecu codes then reset the ecu after because i was showing 23 maf and 17 4th injector but the codes cleared after i put in the maf so must just of been that... whats up with yours what problems are you having?

Disconnecting the maf when it's idling to see what hapens does nothing, it's a myth you sometimes see on here.

And yes, induction kit with a 99/00 maf is likely to prove terminal to the maf and maybe even the engine:(

yeah when i disconnected my maf the engine cut out so the ecu didnt learn how to run without it, but the maf was the problem so i dont believe that works to, ive got a 97 with induction kit but not the crap oiled paper type like k&n which ruin the maf ive got a blitz metal mesh which is dry... apparently the delicate circuits in the top of the maf get damaged easily from vibration which causes them to fail mainly, i didnt have the bracket to hold it in place on mine so it was loose and moving arounf which probably didnt help so got a bracket in now, so why is it bad for a 99-00 to have an induction kit for the maf what about dry types like mine arent they ok?