Hi just joined and might be abit of a long post.
Ive had my scooby for about a month and a half now upgraded from a type r, when i first got it the down pipe was knackerd and that was it.

It just had the standard pipe cat an all as far as i recall because i only drove it for like a week while it was like that it was all ok boosted fine but was boosting abit late because i was loosing everything in the down pipe but asides from that was all fine.

Well i finally got a HKS down pipe decat with a 3" top bit (very technical i no) and got that fitted and ever since then its had an issue where if i floor it the boost gauge goes to like 1.1 or 1.2 like its over boosting but it also feels like your driving through trickle or something because power basically comes in and out like hitting a rev limiter in a diesel or 8v car.

I take my foot off as soon as it does it dont want to damage it but the strange thing is is that it doesnt do it and will pull and rev fine all the way to the redline if i use half 3/4 throttle and don't just mash it in but soon as i use full throttle it just dies again does it in all gears.

Ive been around forums i read various post of things that sound close but not quite the same asides from that its fine ideals smoothly no heating issues dont smoke no real turbo lag no strange noises or anything.
Wondering if it might be because i out a decat on and it dosnt like it or something else because im sure it was fine before and ive had a compression test no leaks or anything.
It will some times pop back fire after it does its strange dieing thing.

Its a 1995 JDM import has the closed deck block td05 turbo z4 ecu and asides from the down pipe and the rest of the exhaust sytem which dosnt look standard but i didnt fit it neither did the guy before me i always run it on premium as well its all standard.

sorry for the long post but wanted to add as much info as i could.
Hopeing someone might have an idea because even though its old i like it but am tempted to go back to a type r that never put a foot wrong.

(wondering if i should spend the 100 or so on a new bit of exhaust with a cat but every scooby seems to be decat with no problem)

(also heard that it might be a fuel cut but have no idea because ive never had that happen so dont know what a fuel cut feels like)

 

i'm not expert but it sounds like youre over boosting and the fuel cut is kicking in. If you have removed the cat and replaced it with a 3" exhaust then the turbo has less restriction and can flow more gases. Owning a subaru is a little different from owning a Honda tin can, if you want to play around with it and change the exhaust, air filter, boost pressure ect then you MUST get a remap.

I changed my up-pipe on mine from a standard one to a stainless steel one and now i get boost spikes. But ive had the car on a dyno and checked the fueling which at the moment seems ok, but it will be getting a tweak in the near future.

 

Google fuel cut defender

 

I had this problem. Faulty coil pack. Could be cracked.

 

cheers i havent replaced anything else done and only got decat because it was cheaper but mabey if i put a cat back on it might sort it i would get a remap but from what i have read u carnt do it to the older cars like mine.

or if i get a fuel cut defender and fit that will that sort it because i dont floor it much very rarely because its my only car aint too good on fuel so i try to drive it abit steady but dont wanna damage anything from over boost.

the one thing i dont get is loads of people seem to fit decat to these seems to be the first most common thing but never get a remap a friend of mine had a uk turbo and decat and was fine dont no if it was a 2.5" or 3 but i dont wanna have to shell out like 500 to get a new ecu then the remap on top dont no if the z4 ecu makes any diffrence heard it was abit better then the normal on for the older cars.

can i check the coil pack myself or does it have to go to a garage for it

 

I took mine out myself, found a dodgy plug aswell it had been glued on because the clip had broken. Sometimes they have hairline fractures in the pack. Mine was letting water/condensation in whilst it was stood, after half an hour it cleared because of the heat from the engine drying it out. Also check the pack nearest to turbo if you don't have a heat sheild it can damage the pack. Change your plugs aswell.

 

also when the it over boost its only for a second then it starts doing that thing and the boost drops back to normal or just below normal

 

i think mine is missing the heat shield from around the turbo i have one around the fluids but thats it
dids yours stop doing it after it had been on for a while because i think mine gets worse the longer i drive it

 

Yeah but that's because it was condensation.
How violent does it cut and is it always the same? Revs etc..

 

its bad say you wanna pull fast and give it a boot soon as u hit about 4k it will do it and will lose nearly all power and just jerk like there is something stopping it its the same in all gears at any revs while the turbo is on soon as u boot it it will happen makes over taking a pain but like i said not if u do it smoothly thinking mabey giving a FCD ago because i assume thats what it feels like because it feels like basicly something is holding it back like when u hit a puddle at speed.

I had a mr2 turbo which i decat and had no problems but that had a fuel cut defender and boost controller all set up so dont no if that made a difference (mr2 was too scary for me)

Otherwise i assume that im gonna have to put the cat back on it which is a shame.
i will check the coil pack as well but everything is expensive right at the time when i have no money.

 

id like to no if i can remap mine or not carnt find much info on it even with google

 

theres a rolling road 50 mins away form me costs 40£ to use its a subaru specialist do you think it would be worth asking them if they canm put it on there and takea look

 

I thought mine was over boosting at first, it was really violent sometimes but sometimes it was more stuttering than violent.
Yeah stick it on rollers and see what they say, they should check it over anyway.
Plugs aren't that expensive.
Think you have to buy a license to map it?

 

Have you tried cleaning the boost control solenoid?

http://www.scoobypedia.co.uk/index.p...ontrolSolenoid

 

cheers for all the help much appreciated
got my booked in for a diagnostic hopefully can sort it

 

Z4 ecu should be 0.9 bar, fuel cut is 1.2 I think?

 

yh seems to hit that 1.2 when it dies and sometimes it will back fire massively then die if i floor it as well