I've been trying to tackle a boost problem and having little to no luck.
Car is a 98 s70 t5se


So far I've replaced all the charge hoses. Turbo (downgraded to a 15 that I had) Put on an mbc. Changed Vac lines. Cleaned Maf. Replaced Intercooler with a used one.


When I disconnected the wastegate vac line it improves abit but not like it should.


I get abit of boost only at low speeds and its not much. Faster speeds it seems like no boost at all


The only thing on the turbo that I reused was the cbv diaphragm but when I checked it, it looked brand new. I do have another one but haven't tried it yet.


The car revs freely in neutral to redline so I don't think its the cat?!


I'm at my wits end on this and have had the thing apart numerous times looking for anything that might be leaking since it must be a major leak since the boost is so low. Would a cbv cause major boost leak (with it having a tear in it? The spring in it or something?


Also the car idles and drives fine otherwise. Only code is evap.

 

I read a thread not long ago on here where the issue turned out to be the catalytic converter. He ended up replacing it and the problem was solved.

I was wondering if that could be related to oil getting pushed into the cat. I read lots of the turbo threads with oil in various parts of the system. Oil will kill a cat.

A new cat is pricey at almost $200 for the unit plus O2 which should be replaced. Believe it or not, O2's degrade with time and should be replaced. With that said i never do it until a code is thrown.

 

I haven't ruled out the cat. Hoping it isn't.
I replaced the diaphragm today and pulled all the ic hosing off and
replaced some of the vac lines again.
I took it for a drive but was hard to tell since it was raining
and didn't really get an opportunity to step on it since there was
too much traffic.

 

That was me with the cat issue. Just unbolt the 3 bolts at the downpipe and pry it loose with a pry bar or something. You dont have to disconnect the cbv (I have a crack in my cbv hose at the connection to the cbv, no apparent issues). Just pry it out enough to have a gap between the two. Start your car up, laugh at the ridiculous turbo noises and drive it around the block, see what that does. Mine would rev fine in neutral too but my case was an extreme one and the car struggled to get past 50.

 

you were correct and it was the cat. When they replaced it they came out with a handful of or ceramic parts that broke apart from the it. Now my turbo is spooling and things are back to normal.