Shudder under heavy throttle?

[dean.ryan]

My WRX has decided that it's going to shudder under heavy throttle. Any suggestions on cause / fixes?

My blow off valve did crap out the other day, may that have something to do with it?

[Timmah]

Unplug AFM, see what happens?

[dean.ryan]

Will do it tomorrow, I know an engine check light will come on for sure.. :-\

[dean.ryan]

I just noticed a crack in a fuel line just before the fuel filter, fuel lines are pressurised aren't they..? so could it being starved of fuel be the problem?

I can rev it right up to redline without it shuddering, it's just under load it shudders?

[kamineko]

lol, time to replace those lines, but really, leaky high pressure fuel line = fuel everywhere = death in a giant fireball so since your still typing its unlikely

after unplugging the afm (good luck with that) i might expect a spark problem. what model wrx is it?

really tho, 'shudder' isn't descriptive enough for an internet diagnostic. save yourself some grief and find someone clued up to ride passenger

[DRFVDR]

could be a slipping clutch as well

[Guest]

like a missfire or whole vehicle vibration

[Jakee]

How many RPM are you giving it heavy throttle at?

[dean.ryan]

 Ichi Ban said:

like a missfire or whole vehicle vibration

Does seem like it might be misfiring, time to pull out the plugs and have a look.

And Jakee: Anywhere from 2.5k upwards, when the boost starts to come in, boost gauge doesn't flutter up or down if that helps

[Jakee]

 dean.ryan']

[quote name='Ichi Ban said:

like a missfire or whole vehicle vibration

/quote]

Does seem like it might be misfiring, time to pull out the plugs and have a look.

And Jakee: Anywhere from 2.5k upwards, when the boost starts to come in, boost gauge doesn't flutter up or down if that helps

Well there goes my idea. Ichi Ban, take it away.

[dean.ryan]

I noticed that after turning my boost tap down, it happens less. Would this be because it's not using as much fuel (dodgy line).. or could the boost tap be bung?

Time for a mofo of a service I think. Get rid of boost tee and new bov

[Swindog]

Take the tap out put it back to stock and have a look.

Pretty hard to diagnose but could be a dodgy plug or lead or intermittent fuel pump or afm. its not throwing a cel (i take it?)

if your bov crapped out it wouldnt cause it to surge, it would blow back and upset the turbo quite abit, youd hear that though it sound like a muffled noise emitting from the pod or filter box area.

[dean.ryan]

 Swindog said:

Take the tap out put it back to stock and have a look.

Pretty hard to diagnose but could be a dodgy plug or lead or intermittent fuel pump or afm. its not throwing a cel (i take it?)

if your bov crapped out it wouldnt cause it to surge, it would blow back and upset the turbo quite abit, youd hear that though it sound like a muffled noise emitting from the pod or filter box area.

What's a cel?

[Jakee]

 dean.ryan']

[quote name='Swindog said:

Take the tap out put it back to stock and have a look.

Pretty hard to diagnose but could be a dodgy plug or lead or intermittent fuel pump or afm. its not throwing a cel (i take it?)

if your bov crapped out it wouldnt cause it to surge, it would blow back and upset the turbo quite abit, youd hear that though it sound like a muffled noise emitting from the pod or filter box area.

/quote]

What's a cel?

Check Engine Light

[DRFVDR]

Clutch slippage,less boost =less hp =less stress on clutch = less slippage

Just an idea

[dean.ryan]

I know it's been a long time since I replied, ECU threw an error 32 or whatever it is for an O2 sensor, once again a pick a part job. I hate being poor...

Now it's gone and blown an injector. Injector on cylinder one crapped out and now working again, not giving it very long before it goes again. Reccomendations for a set of new injectors?

[Swindog]

440s.

[Joker]

knock sensor may be have a fun time on high load/boost

[WRXONP]

Sounds like spark blow out - because of saying more boost makes it worse

Check what plugs are in it - what condition they are and what gap - - also doesn't happen to be a v1 or 2 does it ? Could well be cracked coils if it is

[dean.ryan]

In regards to new plugs, just put a brand new set of Irridium tipped plugs in, so shouldnt be that. Have replaced the 02 Sensor and now runs fine