Car Jerking on Boost
 

Hey guys.
My MY99 WRX is due for a service but just in the last few days it has been revving very jerky when it comes on boost. Im a bit worried so I wont be driving it until my mechanic gets back from holidays and can look at it.

Any ideas? Could it be misfiring? Bad plugs? Coil pack? Vacuum leak?

Im not hugely tech savvy when it comes to cars so any suggestions would be great :)

if its just starting doing it overnight, its more than likely poo fuel.
if its been slowly getting worse it could be a number of things and your mechanic is the way to go.

spark breakdown

Dont rule out the good ol craptastic my99/00 AFMs.

[QUOTE]Dont rule out the good ol craptastic my99/00 AFMs.[/QUOTE]

x2 I had the same problem and it was the AFM.

I was told by several mechanics while waiting to get the car to Subaru that the problem was most likely to be a dodgy fuel pump / fuel filter / spark plug / ignition leads / vacuum leak / boost leak.... subaru replaced the AFM and all was well.

Yeah sounds like it could be many things. Specially a vacuum leak as its happening when it comes on boost. AFM shouldnt be ruled out and yes, crappy fuel could be a possiobility making for dodgy combustion. So many things it could be, good luck finding it!

Not wearing thongs when it happens are you? Cause sometimes that can happen when the heal gets a bit caught on the floormat ey. when it hits the full boost.

[QUOTE=atz 242]Not wearing thongs when it happens are you? Cause sometimes that can happen when the heal gets a bit caught on the floormat ey. when it hits the full boost.[/QUOTE]

he could be wearing a thorong when it happens. or is that a throng? or a sorong? or a sarang? oh i dont bloody know but he could be wearing one

Air Flow Meter +1
does it also stutter when you are trying to cruise?

Actually it does stutter sometimes when I'm cruising. Only started happening recently too in the last week or so.

Does it happen when you are sitting at about 2500-3000rpm and just going into boost from there? especially in 3rd or upwards?

Because mine has just started doing the same sort of thing a couple of weeks ago and mine had a service only about 2000kms ago.

And mine is a 2000model.

At first it felt like it wasnt getting enough fuel, but the more it happens the more it feels like its go in and out of boost, I found if i put my foot into it a lil more it helps :)

Dont mean to Hi-jack your thread, but it just seems we may be having the same problem so no need to start a new one.

[QUOTE=kinga86]Actually it does stutter sometimes when I'm cruising. Only started happening recently too in the last week or so.[/QUOTE]

You can pretty much bet that its the AFM. Get a new one from Subaru. Not expensive for My99/00 models. Its might just save your engine

sounds like the same problem j-rad :(

Dang...Oh well, atleast I now have some sort of an idea on what it probly is.

Now, is this job something I can take to my trusted local mechanic? Or is it a job for a subaru specialist? eg: needs re-tuning etc?

Cheers

surging
 

Wrxstasy (Jaime) has a spare afm,if you want to pm him,he might even let you try it to see if that is your problem.

same thing
 

i had the same problem and was told i was running more boost then the mods can handle, i had ma boost controller looked at and it was faulty, tuned the boost and everything was ok.

[QUOTE=j-rad] I found if i put my foot into it a lil more it helps :)
[/QUOTE]

Be VERY careful. If it is the AFM, you could be driving a time bomb as it could be leaning out you car.

Get an aftermarket ECU and do away with the crappy old AFM. Mine cost me an engine rebuild! :(

Got my car fixed today along with a service. Turned out to be a faulty lead. 4 new genuine subaru leads and OMG it runs soooo well. Very smooth, revvy and powerful :) And it sounds better than ever!