Miss accross the rev range

[Pappu1]

All of a sudden while stopped at lights the car started to shake

Sounded like a miss from the exhaust note

Boosting it seems to run fine ish and pulls ok ish

If u hold gas steady and most rpm under 4 u can had a distinct miss

On higher revs its too noisy to pick the miss

Anyway opened engine bay and no apparent hose or leaks

Engine shaking hard at idle

M guessing it's dud spark plug

Or if I'm unlucky then a coil

Any quick way to test - it's coil on spark v7

What u guys think

Grrr bad time to be having issues as need the car to be running

[Guest]

is it all the time or only when hot?

[Pappu1]

Hmmm just started today on way home

Defenately was warm when started

Drove fine and the while stopped at a set of lights all of a sudden started missing

I reved it and seemed fine but Na it was defnetly missing on low rev and idle

Boosted it to see if hesitated but seems to boost fine

Maybe pull was not as strong as per butt dyno lol

What's it got to do with warm bro?

Hopefully not any bad news

[Guest]

should pull all your spark plugs out and give them a clean.that shacking could have been running on 2 cylinders or something.

[Pappu1]

That's what I'm thinking

Altho sparks were chNged like 1000k ago so not sure whey Wud die so quick

[Guest]

are they good branded ones or shit,cause running high boost on shit plugs isnt a good idea.my gtx used to fail plugs after a week on 16psi.the plugs would be completely burnt out

[Pappu1]

 sti8u said:

are they good branded ones or s***,cause running high boost on s*** plugs isnt a good idea.my gtx used to fail plugs after a week on 16psi.the plugs would be completely burnt out

hmmthey were copper ones ngk..

i thought that wud be fine

the car does hit peak of 22ish so yea bit more than stock and douing abt 35kw@w more than stock..

i wud have thought the copper plugs be fine on that..

was ur one burning out due to too rich (or lean lol whatever makes more sense)

it does not seem to mis on decelration... ???

[Guest]

oh copper ones should be okay.i was running the cheap as one.for 1 they were cheap and easy to get from my old work.,it was running a tad rich,but its sweet,it had a chippd ecu so more fuel no boost cut ect.plugs would last say thursday and theyl be fucked by he next thursday.

owell way to go check your coils.leads and plugs,mayb one of the leads is lose on the plug

also did you make sure all the plugs were gaped to the same size?

[Pappu1]

coil on spark bro so no leads as such

i gapped them to 0.76 wich i suppose are in range for wrx

yea hoping its bad plug hehe

[Pappu1]

update...

this morning on the way to work - stopped at the local postshop for a min..

came back and started car - started running nice and sweet

NO miss or anything and boosting fine as wel

3k down the road it started missing agin..slowly at forst and then bad just like it was before..

grrr...

anyone wana take a guess..... ???

me theory is coils are not seated properly on the sparks and perhaps missing cue to no spark..

if soark plugs had gone than it wudnt have become fine suddenly - all the violent shaking the car does when missing may have jerked the coil in place...??

or u think its some connectors that loose.... ???

[soopersubaru]

 pappu said:

update...

this morning on the way to work - stopped at the local postshop for a min..

came back and started car - started running nice and sweet

NO miss or anything and boosting fine as wel

3k down the road it started missing agin..slowly at forst and then bad just like it was before..

grrr...

anyone wana take a guess..... ???

me theory is coils are not seated properly on the sparks and perhaps missing cue to no spark..

if soark plugs had gone than it wudnt have become fine suddenly - all the violent shaking the car does when missing may have jerked the coil in place...??

or u think its some connectors that loose.... ???

Either an un logged airflow sensor issue (most likely,I.E. Violent missing below 3-4k rpm) or a knock sensor fault.

Get the fault codes read?

Had this similar issue on a BF 5 only logged on the CE system when the vehicle was driven with the CE system active (two Black connectors joined)

Also caught out a knock sensor fault in this way.(occasional stumble/miss at cruise)

Computer did not bring up or log CE at all even though missing below 3k was very apparent, Until i drove with the wires connected when the fault occured.

You may have to drive until the fault occurs with a diagnostic computer connected to identify.

Wont be a coil / ignition issue issue. Platinum plugs are also worth the extra dollar! coppers do fail sooner!!

[Pappu1]

I did a scan and no fault codes came up

Hmmm will try another afm

[WRXONP]

all your inputs look about right ie air flow vs throttle position etc. if all is good i would look at sparks or coils . easiest way is pull the plugs one by one and look at them. the spark plug tells a story of how it runs . and as per what Alex said. the copper ones Are cheap. around 4 buck each at trade. and if your gtx was lunching plugs in a week your s*** is seriously f***ed man. detonation much ? i run bkr6e in mine on 20 Pound and the plugs are fine. i just had some in for 5000km and replaced. old ones still fine but when i change oil i change plugs as they Are cheap. but back to op . pull the plugs man. you'll see which ones miss firing. it will be black and others won't be. . . let me know man.

[Pappu1]

cheers bro..

yea hoping to do that..

i think its a loose connection hehe (hoping anyway)

no wonder ur car is running so well - seeing that u service is so well etc...

[WRXONP]

yeah man always do regular services etc. it could be a dud coil as some times some people don't realise its missing through the whole rev range as subarus have that rumble - beat

[Pappu1]

yea man .. same here.. regular servicing..

have some spare coils which will try ....

[WRXONP]

yeah man pull the plugs and read the story ha ha ha

[soopersubaru]

Wont be a coil, or a plug, or a connector!

Sensor issue, as it is RPM related!

do a diagnostic check....well, worth the money to know for sure.

[Pappu1]

Have done scan and no codes came up

It keeps missing up high in rpm as far as I can tell

Well after 5krpm it's kinda hard to tell but is fairly sluggish so assume still missing

Will do afm clean as well

And worse case will Try swap with a known good afm and updae

[soopersubaru]

As i said earlier you may have to connect the diagnostic computer and then run down the road to find the fault.Sometimes the onboard computer fails to log the fault.

But the diagnostic computer will log, Even a partial fail of a sensor.

Hi rpm miss also? you did not mention that earlier!

Looking more like a knock sensor than AFM, as AFM does not get looked at by the onboard computer when boost is present.

Using 98? plug gap around 0.75 mm?

[Pappu1]

plugs gapped to 0.76

i ran car with logger and it didnt get much knock.. on full boost and no knock - been tuned for that tho

will put on a knocky tune and run again just so i can confirm the knock sensor picks it

have a afm lined up to try (known good one from my brothers car)

hmm i didnt know it didnt look at afm when on boost - does it only look at map when on boost?

[soopersubaru]

Afm plays a part across the range with the standard computer...To a lesser extent above 3500 or thereabouts.

Fuel pressure? rising with boost? Could be the sluggish effect above 3500.

Make sure you re boot the computer when you swap out the AFM with a known good one.

[cuscogtb]

Did you end up fixing the problem?

[WRXONP]

if its running a cylinder down through the whole rev range its pointing at coils and plugs

[Pappu1]

 WRXONP said:

if its running a cylinder down through the whole rev range its pointing at coils and plugs

running a cylinder down accross the rev range -- correcto..

i changed all the sparks and coils yesterday and same problem..

got depresed thinking if had broken a piston ring as bad black/blue smoke when running ..

anyway, im going to individually remove wire to each coil wheil running and see which one makes no difference..

hopefully that tells me which one..

what are the symptoms of a broken ring land?

if one of the injectors is not firing will it have same missing accross rev range?