only had the car a few weeks,but it's getting noticably worse.
Starts and runs perfectly from cold,but after about 20 seconds tickover drops to 500rpm and starts missing.
nightmare to drive around town (chugging,coughing,spluttering) but as soon as its on boost it clears and takes off perfectly.As soon as you let off the throttle it misses again.
It's completely standard and has covered 80,000 miles.
I've only tried new spark plugs at the minute as funds are a little stretched and i can't afford to throw parts at it.
Any help much appreciated.

 

Not sure if this will help, but mine did this after I put a recon. head on. The idle was set too low.
Get the car to normal operating temp, switch off all electrics and disconnect the idle control valve (white connector on top of the unit to which the throttle cable goes to).

Then screw/unscrew the white plastic nut through which the throttle cable goes until you get the car to idle at 850/900 rpm. I find it's worth giving the throttle pedal a little push after every adjustment. Note, a tiny amount of change on the plastic thingy can make a big difference so go slow.

If that doesn't cure it, I have no idea - sorry.

 

it sounds like your fuel presuer regulator or could be your idel speed control valve if it was runnig at 500 rpm it would sound like its runing on 3 because you havent got engough revs to make four cylinders

 

the ldle speed control valve may be sticking or failed,common problem on cozzies,is sits in the throttle housing and is held in by 2 screws its about 2 inches long and about an inch in diameter and has a connector pluged in the top and has a stainless body.
remove the connector,take out the two screws and pull the valve out of the housing,it may be stuck in tight but it will come out
when removed examine the end part as it may be dirty.simply wash the end part in petrol until its clean also look down into the throttle housing and make sure theres no bits of subaru,s in there
before you reinstall the valve put a small bit of vasiline on the o-ring to ease instalation,then bolt and reconnect up and see what happins.
to check if the valve is working,before you install it plug the connector into it and turn on the ignition you should see the end part move

 

Mr Frog.. much as i hate to say this, that is a bad thing to do for many reasons...

The first part was correct, but to adjust the idle speed you must ONLY use the idle speed control screw located unbderneath the throttle body at the front. using the cable as you have done alters the TPS signals relationship between on and off throttle which can cause numerous running and fuelling problems.

Hope this helps.

 

thanks guys,i'll give it all a go,see if i get any joy.

 

Think it's sorted.seems to be the throttle position switch.
Fingers crossed though,it might just be luring me into a false sense of security before rearing it's ugly head again!
Thanks for your help guys.

 

Stu, makes sense, good job you are here to keep an eye on what I say. Dare I ask how both are adjusted then ?

 

Boo Hoo Hoo,still no good.
Throttle position switch sorted the tickover but it's still missing driving at low speed and hesitates when you put your foot down till it's on boost.

 

hi sound s like your over fueling thats why it runs shit befor you get on boost but when yuor on boost it fine its got to be your littel blue sensor on the back of head you know the fuel collent temp sender if its geting a fulse resistence then the car would run quite bad until you get high in the rev its worth checking out the conecti0on as they short out and casue this problem out of the blue

 

Still no good.Removed and cleaned the idle speed control valve but made no difference.tested it whilst out and the end didn't move at all when switching the ignition on/off.rooted through the service history,it's had a lambda sensor and air bypass valve fitted recently.also found records for its last tune at interpro 2 months ago making 219 BHP and 218 lb ft so it obviously was running sweetly.

 

maybe phase sensor check gap

 

where might i find that mate?

 

its in the dizzy i think the gap should ne 0.75mm i think im not sure maybe sum 1 can correct me

 

i see that you said the idle speed control valve didnt move with switching ignition on and off,i dont think this is correct.it should get a pulse initally when you turn the ignition on.get some one to turn on the ignition and then quickly disconnect and reconnect the plug on the valve,you should here and feel a click from the valve body.if not disconnect the plug on the iscv and check for 12v between an earth and one of the recessed pins in the loom plug with the ignition on,it may time out after a few seconds so you may need the engine running to be sure.if that checks out try for continuity in the other recessed plug pin all the way to pin 34 on the ecu main plug connector located behind the glove box (its the lower box the upper red one is the abs control computer).i think you may have a problem with this valve not working and its causing a rich run after you start the car and poor idle when warm and closed throttle

 

Mine did the same, in the end it was the MAP sensor. It has a little bit of oil and it damaged the diaphram inside causing it to miss like a bitch untill it got to 3k then it would be ok.

 

makes sense mate,I'll test it again tomoprrow.thanks for your help, it's much appreciated.

 

yeah give it a try migh be no harm just to eliminate it if it checks out,then try the map sensor as MR COSSIE 4X4 sugests as they can also cause problems like the one you discribe and the best way is to swap with a good one.just make sure the pipe that feeds manifold air to the sensor is not blocked or full with bits of subaru,s

 

hello bro, its possible that you may have a air leak, either the inlet manifold gasket OR the plenum chamber gasket, there is a test you can do, which hopefully somone else can clarify, but this is a common problem and I have just traced a fault on mine to the plenum chamber gasket leaking.

 

just cured same problem on mine with the help of a chap from this site, it wasnt the plenum gasket it was the mixture, co screw on the ecu, you need to adjust it mate. I assume your on L6 or L8, problem solved.

 

cheers boys,not had chance to check yet but i'll keep you posted.

 

been playing with the idle speed control valve again.tried unplugging it and plugging back in as suggested and it does nothing,there's nothing pulsing from inside the body of the valve or anything.checked the feed to it and all is fine so i'm gonna try a new one tomorrow.call me stupid if you want but the sensor on top of the intercooler clicks when you turn the ignition on,i'm assuming this is normal.

 

the amal valve yes it should click

 

thanks mate.seems to me that it must be the idle control valve.hope so anyway,starting to drive me nuts!

 

My new control valve is winging it's way to me as we speak so hopefully should be sorted soon.missfire is a lot worse on damp mornings,do you reckon i've got an electrical problem as well or is it all linked?

 

steviep i know you checked the feed to the iscv but did you make sure that u have continuity between the other pin in the plug connector and pin 34 in the big plug that goes into your ecu,thats the signal to the ecu which controls the valve by earthing it at a high rate of pulse,if that wire is broken between the plug at the valve and the ecu your valve wont work.
you can also check the valve by connecting a 12v supply and earth to the pins in the valve itself and just breifly touching them to try and pulse the valve .
hope it all works out for and it may help cure your second problem
but we.ll wait and see