ok ive had a problem with running cold for about 3 weeks now. when starting the car it will idle very high then settle, this is kind of normal. but if i try and drive it will kangaroo everywhere at low revs. if i hold the accelerator at around 1.5 rpm then you can hear the engine struggling to run and sounds like it firing all at the wrong time. if i rev the engine higher then it will rev up fine and sound ok. soon as it warms up its drivable but not 100% sometimes it will jerk and not run smooth though.

so far i have changed

oil twice, once to 10-60w then back to 0-40w
oil filter
fuel filter
coolant
coil packs
spark plugs

reset ecu about 4 times and never get anything wrong come up.

tonight i changed the plugs and coil packs, went for a drive and still same at cold but not as bad, maybe because weather was better and was -1C last time i took it out, so car was naturally hotter before i started. everytime i got to 4rpm then the car seemed to kick me back and sounded a bit like the turbo overboosting. only happened on full boost though. only thing i can think of is that i decided to change my pfr6b plugs for some pfr7b. has anyone else done this and noticed they didnt work properly??

also i thought it might be the maf sensor that playing up and causing all my problems. i unplugged it and connected the 2 black wires and it came up with the code straight away. does this mean that my maf is ok? is there a way i can test it properly??

another thing i thought of is that it might be my dumpvalve as its only a cheap one. so i bunged some more washers in it to try and tighten it up but then it didnt open much at all, so i take it that was fine. ive reved the engine with bonnet up and can see at stood still it doesnt open until you give it a good rev around 3rpm i would guess from throttle position and noise of engine.

 

when you say the code came up straight away do you mean the code for the MAF?? afaik the maf can cause all kinds of issues when running, also, have you checked the gaps on the plugs? if they are new they might not be gapped properly. If you are getting a code for the maf then change it, if its that it will make a world of difference. Need a bit more info really, what you checked and what you have done, dont use any oil thicker than 10w40, when i got my car, i got with the assumption the engine was blown cos it sounded like someone banging 2 pans together, turned out the oil which was 15v50 had blocked the cam followers and caused upset, cleared as soon as i flushed it and filled it with 5w30, but thats too thin! 10w40 is the stuff to use.
However, oil and filter wont make a difference to the general running of the car, you are looking at fuel air and spark, and the related items.
Saying all that, if your getting a maf code, its a simple fix. Have you tried resetting the ecu?? the other way to test, not a sure fire way, but you can unplug the maf when the car is running, if it stalls then its either ok or just going, if it carries on running as it was then its cak.

 

if it's missing when its cold, it could be the ht leads dirty, take em off and clean with thinners,

 

from my understanding its an early car with coilpacks, he says he has changed them, so it wont have HT leads. if its throwing a maf code, then thats the only way forward at this time.

 

fair enough

 

it only threw the maf code when i disconnected the maf. i was trying to test if the maf had gone caput. im not sure how you test it so i thought ok ill unplug it and see if it still runs ok. car started up and reved it a bit and didnt stall.
then i plugged the maf back in and it still came up with the maf sensor was gone. i reset the ecu and it says the maf sensor is ok now.

yeah i had the problem with the plugs last year. somebody told me to buy pfr6b-11. but that caused the car to do what it doing at 4rpm because of the gap size. i got some pfr6b instead. the plugs i have used now are pfr7b, same plugs just a colder version im told so they can stand more heat. just thought of them as an upgrade.

but i do remember that last year when i changed plugs i left the maf sensor out by misstake when putting back together, didnt notice any difference till i got to about 4rpm then and it juddered around like and idiot and engine light came on.

could my maf be broken but it doesnt come up with a code for it? anyone else had a broken maf? what can i test?

 

i changed oil from 0-40w to 10-60w about 3 weks ago, this made the problem 10 times worse so i changed back to 0-40w thinking it might have been the oil. this didnt help me at all and problem was still there.

 

If its more noticeable when cold it 'could' be down to the lambda sensor. My MY99 would splutter at low revs when cold and drive O.K when warm. If I applied the throttle lightly when cold it would be fine, but any further and it would jolt quite badly. Do a search, there should be a link for a cheaper universal sensor as Subaru charge £130, many people used universal with no problems. Good luck

 

Did you gap the plugs? or just put them straight in??

The maf sounds abit dodgy to me, do a search on here theres a diagnostic somwhere. With the use of a multimeter you can check the voltages/ resistance at the maf to see if its goosed.

What year is the car? Early mafs cost a mint bought new!!!

 

Theres a tell tail sign of a knackered lamba...mpg! If its gone the ecu doesnt get a reading so for safety it overfuels.

 

i didnt gap the plugs no. i just put them straight in. last time i changed plugs i just put them straight in and it was fine.

dont think its lamba sensor as it does the same when warm just not as bad, its pretty much undriveable when its cold. havent driven it far enough to know if its doing alot less mpg. dont wanna knacker it too much and it always drinks loads anyway on boost.

a garage has told me it could be a pipe loose or split so said to get a can of easy start and spay it around all the inlet hoses, if the revs pick up then it will be that hose that is dodgie. gonna give it a go tomoz

 

Get them plugs out and gap them, 0.7mm

 

how do you change the gap size on pfr7b? the problem was there before i changed the plugs though. BUT i did notice that the old plugs had different gap sizes? does this happen due to wear? only very slight but i could see it with my eye.

 

depends how good ya peeper are, the gap needs to be 0.7mm, if its 0.5 or 0.9 it could give you problems, are your eyes that good that you can see a difference of 0.2mm?????????? Get a gapping tool from halfords or your local car care

 

i think the gap on the old plugs might be pretty big actually and i noticed that it was the back 2 plugs that where larger than the fronts. also my coil packs were alot more warn at the back than th front.

i have seen the gap tool that measures the size of the plugs but how do i adjust the size if its too large?

 

Spark plug maintenance tools

The bottom left of the Pocket Multi Tool has 2 slots, insert the bottom electrode of the plug in the correct size slot and open or close accordingly

 

Some gap measuring tools have a adjusting tool built in to allow you to increase or reduce the gap. If they are to big you could gently tap them against something solid but do be gentle as there is no point closing them up to far.

 

ok cheers ill have a look in halfords for one tomoz and get the plugs out again. if this doesnt help then ill be back on here screeming i spose.

 

is it normal for mgk branded spark plugs to come with the wrong gap sizes though?

 

Just take your time. There is no point rushing in and making a bigger mess of it. I had to do that tonight as I am taking the inlet manifold off my STi and trying to get to all the bolts for the A/C is a pain so I decided to have a break and start again tomorrow before I really made a mess of it.

 

im not really rushing into stuff. im trying not to drive the car at the moment cos i dont want to cause damage, getting lift to work and stuff. just asking people and trying to do one thing at a time.

somebody said coil packs, so i checked them and there were large black spots on the back 2 and front 2 didnt look alot better some got some new ones. plus thought i would do plugs at same time.

its going to a speialist next week if i cant get it sorted, but dont know how much its gonna cost hopefully nothing as its a friend of a friend.

its going into these guys MSP | Motor Sport Partnership | Subaru Motorsport Construction and Servicing and i know hes pretty busy at the moment so its just a question of when i get it back and working. but really nice bloke and should get it fixed.

 

Generally, if its plugs or coil packs, they tend to show their weakness just as you're coming on boost when there most underload. This does'nt seem to be what you are describing, if i have understood correctly, you are saying it seems to run rough when trying to rev up from idle.
If this is the case i would firstly check, as you mentioned, all hoses for splits/cracks.
Then maf, then lambda.
And as you asked, the answer is yes, you're maf can be broke witout necessarily showing up on the fault codes.........Unfortunately.

Good luck.

 

is there a way i can test my maf?

yes when cold it idles very high then settles. when driving between 1.5rpm 3.5rpm the car will jult around like an idiot. and struggle to rev. if i rev higher and nearly wheel spin off and keep the rev high then its fine.

when cold if i apply the accelerator and hold around 1.5rpm the car spits and splutters and shakes and normally wont even go to those revs and just stay around 1rpm and shake. if i rev higher then its ok. just anything under 3rpm it wont run.

i left the car for ages after work today running to warm it up so i could drive home. i noticed that after warming slightly the revs would go to 1rpm then i heard a electronic click noise and the revs raised to 2rpm for about 10 seconds then back to 1rpm. then after 5 seconds or so a click noise again and it raised to 2rpm. this repeated for around 5 minutes till i got bored shouted at the car and just juddered my way home.

 

one more quicky, the guy at MSP | Motor Sport Partnership | Subaru Motorsport Construction and Servicing told me to check for leaks in pipes and seals. use a can of easy start and spray onto them to see if engine speed increases. it was dark tonight when i tried and ill have another go tomoz but, i sprayed around and nothing seemed to happen, so i sprayed in the air filter and yeah they went up. i sprayed around intercooler pipes and nothing happened so i sprayed on front of intercooler (fmic) and nothing happened. should the engine speed increase from going through intercooler? if i have a split intercooler pipe then will shuving easy start down it make the revs go up?

 

No the revs won't alter unless is gets fed into the engine, the front of the intercooler is merely where air is forced through for cooling purposes, its the pipes on either end that go through the centre of the ic that feed the engine (unless you had a split in the intercooler that is).
Remember you need to check all the small bore tubing, not just the large pipework. Also around the inlet manifold where it mates to the cylinder heads to see if you have a leaking gasket.

 

if i have a split intercooler pipe then will shuving easy start down it make the revs go up?[/QUOTE]

Yes!

 

ok cool. just thought spraying it on the front of the intercooler would be where air is sucket from and therefore easy start would go straight to engine and revs would go up. same as air filter did.

ive just got myself a boost gauge off ebay aswell so hopefully that can tell me a bit more.

i will get a volt metre from work on monday and check out the readings from the maf aswell. apparently you can see if theres a problem that way. hopefully ive just split a bit of silicone though. seems wierd how its only on lower revs that its not working. would have thought that higher revs would make hole larger and not run as well.

 

sound like the plugs, have you gapped them correctly yet?

 

ok i went for my MOT today and it wouldnt even pass an idle emissions test. last yeah it didnt pass a full test so he did it a bit dodgie for me. today it wouldnt go under 0.950 on CO levels. he couldnt do me a dodgie one as the ministry had been round. so i can either get it sorted or wait till hes willing to do it a bit dodgie for me.

i dont think its a spark problem as it feels like the car is boosting all over the place. i had the problem with the gap sizes last time i changed them and it actually miss fired and you could hear the engine making noise with wrong gap sizes. this time its like its going on and off boost if i floor it. stood still it will rev right up fine. accelerating slowly it will go all the way through fine. its just if i nail it.

im getting a boost gauge so see what that tells me.

anyone had a faulty lamba sensor before? or co in the manifold? what can that cause? would that explain my high emissions? but they have always been pretty high i get around 8.2 CO on full revs.

 

have a check of your coolant temp sensor too, that can cause high emmisions, the lambda does the same too, but to be honest, i am not sure about the rest of your problems. the idle air solenoid can cause some weird problems, but mine has descided to not work and my idle is all over the place, and it doesnt rev very well.