unsteady boost and high mpg!
 

Hi, when in forth or fifth gear as the boost comes in it rises to 18 psi then drops off to 11psi then keeps on rising and falling, it never really settles.

I dopt think its fuel cut because it doesnt feel like its hitting a brick wall when it happens. It feels like its kangarooing!

I have cleaned the boost solenoid out with the green and black plugs connected, but when i turn the ignition off the solenoid keeps clicking, is that normal?

also the its using alot of fuel at the moment!

Its a MY00 UK turbo with centre decat 5 inch exit backbox and a bailey dump valve?

Any help would be appreciated!

i also am having same trouble, i will be looking at coil packs on mine also have u unpluged the green and blk plugs as the only connected for fault test and ecu reset

yeah i unpluged them after cleaning the solenoid, that was the only way to stop it clicking!

I also changed the MAF and lambda sensor as i had high o2 reading and the scan tool said there was a MAF problem.

Boost leak somewhere maybe?

Coil pack aswell as said above

Ive checked all the vac pipes for leaks and they seem fine, i put a new silicone intake pipe on as the oem one was split at the bottom causing it to leak!

Is there a way of checking the coil pack?

my 2001 wrx bug wagoon is doing the same! ive been pointed in to the direction of my waste gate not closing properly! im going to try changing my actuator on the turbo! ive also had a new lambda fitted due to it failing the emmissions, it lowered the emmissions still failed test though due to them being slightly high!

Saying that I cnt really see a coil pack making ur boost fluxuate like that, id still double check ur vac pipes, only needs to be the smallest of slits/holes! Sounds stupid but if u have done anywork on the car recently double check it all, I forgot to plug my maff in on an old puma after striping that! Cldnt work out why it was running like a pig lol

fuel pumps too guys, low fuel pressure at high rpm and boost

The only work ive done on it recently is replacing the inlet pipe but i double checked i replaced everything!

That was about 5 weeks ago. the problem with the boost has only been there for a week or so!

I'll have to check all the vac pipes again!

Would the restrictor pill cause a problem if there wasnt one fitted? When i bought the car it had a manual boost controller on it but i took it off and put it back to standard but there was no pill!

Maff maybe? Not to sure about the restrictor pill, ain't really read alot into them, I'm still learning about imprezas myself, im guessing it wld have happened as soon as u took the Mbc off if it was the pill tho

A my99 uk car will have a 2 port boost solenoid fitted as standard,a 2 port will not be able to handle boost correctly with the restrictor pill removed.You need a 3 port fitted and mapped to be able to run with no pill,check and see what is installed on the car.;)

It has a 2 port fitted.

I replaced some of the vac pipes today, warmed it up and took it for a drive, now it will only boost to 10 psi!

Its no where near as quick as it was but at least the boost is steady!

How can i increase the boost back to 15 psi?!

I have this with my bugeye. My mapper has got rid of most of it by changing the boost correction tables during a mapping session. We will be refining this when I fit the larger turbo but it became apparent after fitting a better flowing exhaust so I assume it was down to the boost control not reacting quickly enough to the turbo spooling up.

When you changed the vacuum hose did you remove and refit the brass pill that it is the pipe that runs from the boost solenoid to the wastegate. It is the size of the hole in this pill that regulates the amount of boost the car will run with a 2-port fitted otherwise you generally run wastegate pressure (which for a newage WRX is 7psi).

Ive just been out and looked at the old vac pipes and there was a pill in one of them!!:Whatever_

Just fitted it back on and it now boosts properly but still rises and falls in forth and fifth gear.

Could it be a problem with the pill being the wrong size?

The pill is fitted between the turbo nipple and the T-piece that connects to the actuator and BCS, is that in the right place?!

I can't be 100% but it sounds like the right place - I have a 3-port so no pill fitted any more:wonder:

Does it have an induction kit, decat and/or freer flowing exhaust - if so the actuator or boost control might not be reacting quick enough as the turbo is spooling up quicker. I bigger whole in the pill will reduce the fluctuation but at the cost of max boost.

When I had my car mapped the problem cured be corrected with tweeks to the boost correction tables provided we kept max boost to 1.3bar or below, @ 1.4bar it became more difficult yo control.

I'm sure someone more experienced can shed more light on this.

It has standard air box and filter fitted.

I have put a centre 2.5" decat and a big bore backbox with a 5" exit.

What size would i have to drill the pill out to?

Sounds similar spec to mine when it started. I wouldn't know about the pill size TBH, you need one of the experts to come on and talk more. FB Tuning is the guy who does my mapping.

i have an avc-r to control my boost, no resitcer pils in any of the lines,

Yes that is the correct place for it on a std 2-port BCS-equipped car.

could be that its mentioned, but I once fitted a #¤&#¤% big turbo on one of my cars, and had the same problem. Turned out the boost control valve could not ventilate the excess pressure once boost came on.

a restrictor did the trick, but note that a restrictor can increase your boost pressure.

try swapping out the bailey dumpvalve for an original and see what it does..

you are describing a boost leak and my money is on the dump valve