I have been having boost issues for nearly 10 months now. What happens is when i reach 4000-5000rpm my boost runs up to around 15psi and then instantly cuts out to a constant 0psi and the revs dont build up, literally like hitting a brick wall.
I have had a new MAF, tried a 2nd hand boost solenoid, had all the hoses checked and some replaced, different actuator and its really annoying me now, car wont even push over 110mph. I have been told to block the vacuum pipe to the actuator and take it out and if it doesnt boost up properly then it could be the turbo. Any ideas guys??
Also the car is a 98 uk turbo saloon, will the turbo be the TD04??
Sorry for the long essay, any help would be gratefully received.

Mat.

 

Hi Mat,
It sounds like "over boost" which is causing the "fuel cut defender" to come into action and this is what makes it feel like it's hitting a brick wall .
I've discussed this a few days ago with another member (Lummox), heres the link (hope it works);

https://www.scoobynet.com/general-te...preciated.html

Do you have a "boost adjuster"? manual or otherwise? When my car was doing this I removed an after market boost bleed valve (adjustable brass type) and this sorted my problem. Also maybe worth checking your boost solenoids pipe work, paying particular attention to the bottom pipe which should have a small "pill" inside it. If the pills not in there or the wrong size I've heard that it can cause over boosting to.
Also if you do a quick search there is a guide to cleaning your boost solenoid correctly and things to look out for which may help you narrow down your fault search.
Goodluck, hope I've helped, Gareth

 

Hi GMballistic, thanks for the reply.
I dont have a boost adjuster or any thing like that, only mods to the car are baileys DV, manifold, decat and 3" straight through system all of which was on the car when i bought it. It ran fine for a few months then suddenly decided to go like this.
If it is overboosting, what can i do to cure this??
Also after looking at this link...https://www.scoobynet.com/technical-...-solenoid.html
i stupidly havent tried it with the plugs connected, i will give this a go but i take it i squirt it into the top pipe on the 2port type like mine too??
Thanks
Mat

 

I had the same problem on my car. Turned out it was the crappy baileys dump valve, it coudnt keep up with boost changes etc. I binned it and ran no dump valve, works perfect now

 

Interesting...Could you hear any noises from this?? I would of thought you would hear the air escaping from it. Guess its worth a go, time to source a standard re circ valve.

 

Didnt hear the dump valve as such, more the lurching of the fuel cut. It was really bad in first gear. And if you're running more then standard boost this just makes it worse. Turns out the DV i had just couldnt cope, i recon it was so old the spring in it had gone, could press it down with 1 finger.
After going to no DV everything went ok. Not had any issues so far, and feels a little quicker, but thats probably all in my head

 

my 99 wrx was having boost issues. the boost was sometimes good then fairley poorand was acting hesitantly. I was getting a knock sensor and map sensor fault. so i took a fantastic bit of advice off of this forum and cleaned my boost solanoid and tubing which it is connected to it, with carb cleaner. my car is running sweet as a nut now and the boost is so smooth and responsive. so i would recommend that. so thanks to all that recommended it to me

 

Ive tried cleaning out the boost solenoid, and it hasnt made a difference. Going to re fit the standard re circ valve back on when i get one and see if that makes a difference. If not then i guess its big money

 

I'd definately go back to the standard recirculating valve and see if this cures the problem. I did wonder with mine before I solved it whether it might be possible that the actuator on the turbo was sticking open/closed and causing me problems. This might be totally in the wrong direction but it's one more thing to throw into the mix. Hopefully not going to cost you big money but nobody said owning a Subaru was cheap

 

vta's dont even do this ? having no dump valve is not good at all as it leaves 2 much air in the plenum for the turbo to boost efficiently and lag will be an issue , a fuel cut defender allows you to go above the factory fuel cut safety feature on standard subaru ecu's u can pick them up for 50 quid s/h nowadays wha happens is u go above 1.2 bar of boost and bang , a sore chest and fuel cut sometimes the ecu will retard the timing and cause u to be in limp mode (( 0.5 bar of boost , 8psi ) but mostly just gives fuel cut , you are overboosting , make you actuator rod longer 1/2 a turn at a time until the fuel cut goes away , also try connecting the two green connectors underneath the steering wheel and turn the ignition on but dont start the car u should then hear the boost solenoid ticking like mad if it dosnt click ( clean it properly ! ) if it still doesnt click the get a new one , this is mostly caused by overfilling the car with oil , it will and is well known to cause overboost due to the higher oil levels the oil manages to work its way to the compressor outlet nipple on the face of the turbo and clogs up the boost solenoid hence causing overboost then fuel cut due to the boost solenoid being clogged with oil it cannot bypass the exhaust gases away from the turbine and weeeeeeee! its damn fast lol! but aint good if ur cars not tuned to run high boost , failing all this u might be missing the brass restrictor pill in the hoses coming from the boost solenoid as missing this pill can also cause boost issues like overboosting being the main one , hope this helps m8

 

Well thanks for the input fellas, appriciated.
I have had another actuator fitted and played with at my garage and that didnt make a difference either. I have just bought another standard re circ valve to try. I removed the baileys one and can push the spring in with my finger fairly easy, is this normal or should you not be able to move it by hand. Also will i be needing any other different pipes to re fit the standard item back on??
Thanks
Mat

 

anyone know if i should be able to move the spring in my dump valve by hand??

 

yeh u should they are quite soft so the vac can actually pull them shut , u will need the two small pipes for each side of the standard dv to refit it they are only bout 2 inches long dont remember the diameter though ? and they have the squeze clips , not jubilees

 

have read all advise here and will try to adjust the actuator rod , but i have a forge d/v and have recently fitted boost guage and boost controll valve which i set to 1 bar to be safe !! ran sweet for 1 day then next day the brick wall thing so hav now got it set to .75 bar n seems fine now so am asuming its fuel cut off????but am gonna throw a paddy , I WANT 1 BAR lol

oh yeah just incase it helps am in a L reg waggon with a sti red top v 2 engine implant ??

 

Right, jus put the standard re circ valve on and the problem is still there! Im fuming! I really dont know what to do now.
Even if my car is over fuelling, what can i do about it? why is it doing it?

 

Does this only happen when trying to go above 110mph, or does it happen in 3rd and 4th gear to?

 

Happens in first, second, third, forth and fifth....It wont then pull past 110mph and revs will hardly build.

 

same symptoms as mine , having mine remapped soon to cure it hopefully.

dan

 

Fair enuff mate, but the way i see it there is something mechanicaly/electrically wrong and i would prefer to fix the existing problem rather than "mask" it.

 

am currently isolating a customer car with the very same problem except in a bugeye wrx. there are no check engine or whatever and subaru dealer cant even find the problem. I will try this weekend replacing the throttle body as i would suspect the TPS sensor is failing hope this cure my problem as well

 

ball172: check your fuel pumps. i have recently replace my customer walbro fuel pumps with a stadard sti pumps and its now reving all the way to redline. There is still slight hesitation so will replace his sparkplugs

 

i am having same troubles but changed plugs and 1 faulty coil much better but still has slight hesitation how would i get hold of details of pipes and where they go and what should be in them ie valves etc

 

after replacing the sparkplugs its now running smoothly with the new sti pumps will now go to the dyno to have the A/F ratio check and hopefully get it remap again

 

Fair play mate, i have checked the coil but that seems fine. Had the garage check my plugs when then done a pressure test and they said they seemed ok and fairly new. I could check my fuel pump but tbh i think its something more than that, i do tend to run my car on less than quarter fuel for alot of the time! hmm