optimus

Hi everyone,

Just wanting to make sure i'm going to be checking the right things and if there are any other pointers.

Car is a 1995 wrx saloon, standard bar an vta dump valve (arc one fitted from japan) and a decat downpipe (fitted by me) the rest is standard, no ecu or airbox upgrades.

The car has this issue where it only boosts to 0.5/0.6 bar pretty much all of the time which although i presume is 'safe mode' the car still drives nicely pulls all the way round the revs and doesn't cough or splutter etc

However...every now and then it will burst into life and jump to 0.9/1 bar (which i believe is standard) and then for the rest of its life its back to 0.5/0.6

Things i have checked:

cleaned and tested boost solenoid
checked majority of intercooler/turbo hoses
replaced dump valve with a known working vta (haven't yet found a RC one)

things I intend on checking:

wastegate
fit a manual boost controller


is there anything else i should be looking for? I've got this weird theory in my head that the wastegate flap could be jammed open but if this where the case would it hold 0.5 or would it just loose all boost?

I'm also assuming that if it were to be in 'safe/limp mode' the revs would be restricted not just the boost? not cel lights are coming on...

I'm not mad at the ol girl yet because it does drive perfectly well it just clearly not running 100% right!

Thanks

r1c

iTrader: (9)

Vac pipes, restricter pill, air leaks. It and it you have no fault codes?

optimus

i've checked that there is a restrictor pill in there and given the whole lot a good clean (although i haven't pulled it out to see if its correct but the car doesn't give off the impression that someone would have tinkered with that)

vac pipes are the majority these the ones on top of the manifold where the boost gauge goes into etc and the ones in/out of the boost solenoid? If so have checked these.

and fault code wise none , it did have a speedo fault code when i first had it which i sorted by fixing the speedo and resetting ecu.

Its not even like its really intermittent its pretty much never working and then one corner or straight bam you get full power for a few wonderful seconds!

thanks for your reply

rb5 stu

You cant fit a decat downpipe and not get it mapped. the car is prob trying to protect itself from overboosting.
You need it mapped.

optimus

Hi while I appreciate its not good to have a decat without a map in my experience these older cars can run without a cat and have no serious Ill affects besides a bit of overfueling?

It's not hitting boost cut otherwise I would have thought a. Fuel cut would have come in and B. It would have mentioned excessive turbo pressure on the cel? Plus its only seeing a maximum of 1 bar if it's lucky through creep which is below the threshold I believe?

I don't think its over boost that's causing this issue as it was an underlying fault before I fitted the decat.

Thanks for your reply :-)

JDM_Stig

iTrader: (3)

I ran a FCD on my decat`d 95 wrx on a Z4 ecu with no problems.

r1c

iTrader: (9)

Do you have a decent boost gauge fitted?
As you are getting actutor pressure it sounds like a control issue if some sort, do you have access to a vac pump, ie Mityvac or similar?
Your waste gate must be working as your getting pressure.
Are 100% your vac pipes are good? It's the main cause of turbo faults and very easy to miss!

optimus

It's a brand new Tim boost guage so not of defi quality but not an eBay jobby either I'm sure its right?

I've got access to a workshop so sure there must be some guage there I can trial?
But as I'm trying to learn so if I'm getting that 0.5 the rest of the time that would suggest actuator pressure therefore it's working and its something else?

If I were to fit a mbc that would bypass the electrical side of boost?

Thanks everyone I do appreciate it

r1c

iTrader: (9)

You could but make sure you start of with the mbc, at the lowest setting and work up, it's a good diagnostic tool, but once fixed id remove it and go back to your solenoid. It will only rule out a faulty solenoid or electrical circuit fault, you really need to rule that out, also check actuator operation, using a mityvac or similar.

r1c

iTrader: (9)

How does your boost gauge behave when driving?

optimus

It moves from vac to pressure normally and holds at 0.5 quite comfortably when you are on power it doesn't skip around or is that not what I should be looking for?

Cheers

r1c

iTrader: (9)

Have you checked the actuator movement yet? You could have a weak actuator spring, is it always .5 bar?

joz8968

iTrader: (13)

Why not temp. disconnect the electrical connector to the BCS? Then, if the boost peaks or holds to whatever psi/bar rated spring is in the w/g act., you'll know you could have an issue with the ECU's signal or the BCS itself.

Then, I'd also rule in/out all the vac lines to/from the BCS, by simply temp. connecting the comp's outlet nipple directly to the w/g with a short piece of vac hose....

Depending on what boost you get to see during both of these tests, should hopefully steer you to either a ECU/BCS/MAP, vac line/s, or actuator issue. It'll give you some idea of the area to concentrate on.

Probably, lol.

If all the tests still yield a boost pressure of 0.5barg, then chances are it's the w/g at fault in some way e.g. spring, rubber membrane, rod/flapper linkages or whatever. (Or indeed the turbo, itself).