Hi,

I'm having a problem with hitting fuel cut at the moment. The problem has just appeared today, as I discovered when trying to overtake a lorry on the motorway. As I accelarated in fifth, boost came on very aggressively then the car hit fuel cut.

It seems the problem appears in all gears, so it doesn't seem to simply be a case of boost creep in 4th and 5th as is generally the norm when this happens. I'd just filled up with v-power, but I dount this is of any relevance. The weather is also quite mild at the moment, albeit very wet and rainy, so I don't think it's down to lower temperatures.

The car is an STI Version 3, standard other than a Hayward & Scott Up-Pipe, Magnex back box, and a silicone turbo inlet. Had I just fitted these parts, I could have understood, but they were fitted months ago and I have never had a problem.

The car was recently serviced, and I changed the plugs from pfr6b's to pfr7b's, and swapped the airfilter for an STI item in the standard airbox. Not sure if either of these could be relevant, but thought it best to mention anyway.

Car runs fine otherwise.

Help!

 

It could be the silicon hose's one of my clips worked loose several months down the line, felt like hitting a brick wall at around the 3k mark.

ray t

 

Thanks ray, any idea which hose it was?

 

on mine (my00) it was the big one just to the front and left of the intercooler (looking from front of car), the threads on the clip had worn and if you tried to tighten it anymore it would jump allowing the hose to expand under boost pressure then dumping it to atmosphere. It was confusing as you could drive it around "gently" and all seemed fine. But check all your clips it only takes 1 of them to let it all go.

ray t

 

hi i am haveing the exact same problem. i have been told so many different thing that it could be, please take a look at my post
https://www.scoobynet.com/general-te...ease-help.html
if you do find out what it is then please please let me know.
i have had this problem for 4 months now
kind regards david

 

I have seen suggestions that it is because the air is colder and denser, hence higher boost in winter....

 

I know colder weather can have this effect, but as I said it's been mild so can't be down to that.

 

the hose to the intercooler is a good one to check, mine does it at times as someone above mention the jubilee clip jumps back if it is to tight and this is what has happened on mine, so what happens sometimes when you boot it the pipe pops off the intercooler and then when you lift off the vacuum pulls it back on again

 

i had the exact problem last week it did my head in. i sprayed the maf and cleaned the boost solenoid with carb cleaner tuesday and everything is fine mate. try that. do a search for cleaning boost solenoid. i took the elbow thatcomes of the air box off so i could easily access the pipes on the solenoid.

 

I'll give the solenoid a clean next week and see if that helps. I've not checked to see if there are any rampaging hoses so will take a look for thsoe tomorrow. Fingers crossd it'll be an easy fix!

 

The boost solenoid mentioned in one reply above, is this controlled by the ecu to create the correct boost pressure? Not that familiar yet.
i'd be inclined to check the vacum hose from that to actuator for lose connection, hole or collapsed section.
also check the actuator is still in good order and not just holding shut creating infinate boost.
cheers

 

Sounds like the wastegate isn't opening - and agree with the checks in RR's post above.

 

I had initially thought it could be actuator related....

When I put my foot down, boost builds very rapidly and feels stronger than ever before....then *bang*, it hits fuel cut.

How can I check if the actuator is faulty?

 

if you can get hold of a air compressor you can blow air in to pipe leading to it.
ony need about 8 psi to see it move. don't blow 90 odd psi or it will blow
if it is faulty you will feel air venting out a very small hole meaning the diaphram has gone.
you might be able to use a foot pump with football adapter to aply some air pressure. very crude i know but if it works!!!!!!!!!!
just looking for it to move gently.

 

just another thing,
does the solenoid on the subarus intruduce boost gradualy via ecu and valve. or is it full boost all the way to peak pressure.

worked with some cars that the ecu controlled/overide the boost pressure if it felt the engine was to warm. fail safe
cleaver stuff

 

Right.....

I've checked all of the small vacuum pipes from the wastegate and solenoid etc, and all seems to be in order. I cleaned the solenoid using carb cleaner this afternoon too and it's made no difference.

The only thing I haven't done is tested the wastegate, as I need to get a pump of some sort to get air into it.

Something else though....

Over the last week I've noticed the car's exhaust sounds quite a lot louder and "burblier". I had the exhaust checked at the garage and it's definately not blowing anywhere......could the increased boost have knocked the insides out of the cat? Any other suggestions?

 

if you cant get air to actuator. try blowing or sucking on it to see if its air tight. should not be able to do either.

 

sorry mate i forgot to mention. when i cleaned the boost solenoid i also sprayed the maf sensor with carb cleaner 2. try that mate

 

I'll check the actuator tomorrow....seems the likely culprit. If it's not that then I haven't a clue what could be causing it

 

I've been out having another poke around....and thought I'd replace the actuator hoses just in case, as they were starting to feel a bit brittle.

The short one which attaches to the actuator nipple had a tiny hole in the side....so this seems to have been the cause of my overboosting. Put everything back together with the new hoses and it's back to normal - no fuel cut.

Thanks to everyone for your help...it's much appreciated.

Cheers,

Brian.

 

Well.....after a day of not hitting fuel cut, my problem is back

I pressure tested the actuator and found that the hose was leaking slightly due to a poor seal on the actuator nipple. This was remedied with some better clips and I heated the hose up to make it slide all the way onto the nipple. I then tested it again and found no leaks.

I took the car for a run and straight away it hit fuel cut again

I'm starting to think my catalytic converter has broken down, leading to a "de-cat" scenario which is causing my overboost problems. The exhaust seems to be getting louder and burblier by the day, but is not blowing from anywhere. Is this possible?

 

Do you have a boost guage and what numbers are you getting?
Does this happen in second???? Third, Fourth and Fifth???

 

I don't have a boost guage so am unable to tell what I'm hitting, but presumably it's simply producing as much boost as it can before the fuel cut (not sure what pressure fuel cut is on the version 3). It does it in 2nd, 3rd, 4th and 5th. 1st gear seems to be too short for the boost to get high enough to hit fuel cut.

It's certainly running higher boost than it was before....it breaks traction very easily in 1st, 2nd and 3rd, and "sounds" like the turbo is working a lot harder. I'm driving it very tentatively at the moment as I'm terrified I'm going to cause serious damage. The engine let go at this time last year so I don't want to end up in the same situation again.

 

The fact you are getting boost cut in second indicates that the actuator is staying closed for whatever reason and from what you describe, it rather sounds like you are getting massive overboost due to closed penny valve.
So that leads to the waste gate actuator. Is it in good condition and properly attached to the bracket? Is the pipe work to the actuator in good condition? Trace it right back.
If there is nothing obvious then it is a matter of checking out the boost control hardware.
From what you describe, it does not sound like a desintigrated catalytic convertor but more that the WG is not openning.

 

Using a GBE valve it would be possible to replumb your pipework quite easily and determine if that brought it under control.
See what progress you make and I will loan you a GBE valve if that looks like being the way to go.
running a turbo car without a boost guage is a bit like flying blind.

 

At this point i would,
Run a pipe direct from intake to actuator. to determine if your boost solenoid is the problem. ie stuck shut.
you will only be running at actuator pressure then. which is low.

also if it over boost again in that state you will know then the actuator is not opening.......

 

The actuator appears to be in good condition, and moved quite freely when I applied pressure using the pump.

I'll double check tonight if it's hitting fuel cut in second gear. I thought it was but now you've mentioned it I'm starting to doubt myself. If it was only happening in third and above, would this suggest something else?

Is a GBE valve a manual boost controller? I have used these on an evo and a starlet turbo that I used to own which started hitting fuel cut due to free-flowing exhaust being fitted and found them quite effective.

Thanks for all the help so far.

 

Rapid Rabbit's suggestion is a good one too.
The GBE is a manual boost valve. Cheap and effective. I can loan you one to try if you wish to avoid an unnecessary purchase.
To hit fuel cut in second indicates there is no control whatsoever on the wastegate. ie it is firmly shut.

 

I've just driven the car home tonight, and it doesn't hit fuel cut in second, only 3rd, 4th and 5th. So does this mean that the wastegate is fine?

Should I now be looking at the boost solenoid, and possibly cleaning it again more thoroughly?

Thanks for the offer of the GBE Vlave Harvey....where about are you based?

 

Send me your postal address via e-mail and you will get it on Tuesday.
I am Darlington. harveysmith1@btopenworld.com