dear all,

ive has my 93 WRX for just over 12 months and its always had the same problem. Randomly, it won't boost over 0.5 for about 30 mins then hey presto back up to 0.8???

I bought the car completely standard ( de restricted) and it did it then (fine on the test drive...) the only mods ive done are: a K&N panel filter, Forge VTA dump valve, 3" decat straight thru exhaust (LOUD! ha ha ha) its ran on V-power all the time.
Scooby clinic, Foresters (local to me), have had the car and can't find a thing wrong with it, no fault codes showing, no leaks etc.
Ive had new plugs, coil pack, air flow meter, boost solenoid, ECU, knock sensor, O2 sensor yet for half an hour or so every week only 0.5bar .
Ive tried a bleed valve ( set up for a max of 0.8bar) from the actuator to the compressor to by-pass the boost unit on the wing and it boosted smoother but 3 days later.....0.8 on the standard boost gauge but you could tell it was only 0.5 someone please help

 

you could have a blockage in your boost solonoid or restrictor in the bottom pipe of the boost solonoid..basically buy some brake cleaner..blast it into all the ports of the boost solonoid and the pipework(especially the restrictor as mentioned) Oh and dont forget to connect the green connectors under the steering collumn and turn on ur ignition..this should set ur solonoid clicking its head off..give ur brake cleaner another good blast into the solonoid ports then leave it for a while to dry out.
Other than that, you could have a leak in your intercooler pipe(even a small pin ***** hole) or a leak in your boost solonoid pipework so give it a thorough inspection in the light of day
Sy

 

This may sound a little obvious but, is there a problem with the boost gague you are using? If a place like Scooby Clinic cant find a fault. Is there a noticeable difference in performance when the 0.3bar reduction is in place? Do you hear any noises like gushing air? (had a DV stick open on me on ocasion due to the spring becoming less springy).

 

i use to have this problem on my MY03 wrx... some ppl say it;s because of bad quality fuel.. and the ecu detects detonation... thus lowering the boost to save the engine.. some say the solenoid... well i have no idea..
but after i installed a boost controller.. the probelm is resolved..

 

If your gauge says 0.8 bar then the car is boosting to 0.8bar.

I'd check if the car is pulling timing. Possibly some detonation?

 

cheers guys for your answers.

ive cleaned out the solenoid, vacuum pipes (restrictor one too) multiple times over the year ive had the car and its still them same. the intcooler and pipes were swapped for one from a perfectly working 93wrx yet same problemIt'll boost nicely at 0.8 all day long then suddenly 0.5....an hour later it'll be back at 0.8......strangley when the car goes back to normal it boosts the best it ever does
I run the car on V-power from a busy garage, ive tried Millers octane booster every so often but suprise suprise....randomly 0. bloody 5 bar!!!

would a remap cure it????

thanks again

 

I had a similar problem on a MY99 - changed allsorts, and nothing made any difference. As you say, every now and again, and without reason the boost would drop off.

I eventually fixed it (short term) with a Manual Boost Controller - at the time the best £20 I had ever spent. I later replaced the MBC with an Electronic Boost Controller and never had the boost drop again....

 

GWS73.

Thanks for that mate.

Ive fitted an old bleed valve form the actuator to the compressor vacuum hose so the solenoid is now redundant.
It boosts to 0.8 but sometimes the standard scooby boost gauge says 0.8/0.9 but you can feel its only 0.5, as you know yourself theres a big difference.

what MBC did you use and how did you fit it???

 

Had the same problem with my94 classic and it turned out to be a faulty boost gauge causing boost problems ! also if you have a fully decated exhaust from the turbo back , surely you need a remap to run a decat downpipe as fueling and timing will be wrong with the standard map , maybe that could be causing it ?

 

It was just an eBay special. The fitting instructions were supplied - basically 2 pipes (IIRC) one to the actuator and one to the turbo (I think... ) which left the boost solenoid redundant. For the sake of £20 it might be worth trying one - just don't get too giddy turning the boost up!

 

iv got a dawes device, which i did have fitted on my car...taken it off now as iv since had a remap... You could raid your piggy bank if you can spare £200 for an esl chip (enduring solutions) as andy can set the map up to your cars current spec & mods fitted.
Other than that, you should find out what your fuel cut is on your car..(think it'l be about 12 psi) and stay safely below that wen setting up your bleed valve/mbc.
i would say 11psi would be plenty taking into account your running on a standard map.

 

would also check your turbo actuator, possibility that it is sticking slightly open thus reducing your boost pressure although your boost gauge would say your running more boost

 

have a friend who is also experiencing these problem in a sti 02 . have try replacing the fuel filter n check the pump as well as cleaning the solenoid n replaceing it to no avail. anyone has any ideas on these matters?

 

I had same problem on my 94 wrx it turned out to be an intermittent fault on the boost solenoid till it eventually went then I found what was doing it. It wasn’t much fun in the wet when your boost suddenly shot from .5 to 1 bar on a roundabout

 

Cheers for the replies guys.

Ive changed the boost solonoid 3 times,cleaning them out with brake cleaner evey time, replaced the vacuum hoses.
I have'nt tried replacing the actuator as you guys mentioned that it may stick sometimes. I thought it could'nt be that as when its at 0.5 its exactly 0.5 not under or over. Its as if something is holding it at 0.5 then 30mins later tadaaaaaa 0.8. Im going to try an ESL chip to see if that overides whatever is making it play up occasionally and have more fun

On the other hand could it be picking up a bit of det thus reducing boost then det goes away the hey presto back at 0.8.
While I think about it, when I had the 3" de-cat fitted it did the 0.5 thing three times in 20 minutes??? then it went back to normal (well....playing up once a week!)

 

hi,

i had a similar problem with my 93wrx too when i 1st get my car. it running on 0.5bar which show no error code. my mechanic then helps me to instal one MBC and it was running happily on 0.9bar.


but then....it overboosting now.....so my mech helps me to remove the MBC and test-run. it still overboosting. running on stock boost n it can raise up beyond 1.2bar with full throtle...the ecu boost cut is at 1.2bar.

anyone experience this?

 

Dont think it will be det to be honest as the early ecu's are very slow to increase timing etc if it has detected det and pulled timing.

Something else I have thought of, do you still have the standard TMIC?
I had a problem once where the hose connecting that to the throttle body would move under boost and leak out air, but as soon as you lifted off the vacuum created sucked it back into place, took a bit of head scratching that one!

 

yep,

still got the standard TMIC, no leaks, all clips are tight, no movement anywhere.

When I brought the car and the problem happened, I took it back to the guy who imported it and had booked it into Frankenstein motorsport in Leighton Buzzard.

The report sheet said "checked all circuits and live data, found knock sensor pulling timing and lambda not correcting. replaced knock sensor and lambda sensor, road tested boost at 0.8bar. all in order"

Ive also forked out on loads of new parts including replacing the above

im wondering why would it do the 0.5 thing 3 times in 20mins when I had the decat downpipe fitted?

spoke to Adam at scoobyclinic who stated a remap would cure it, hence my question about an ESL chip

 

When you swapped your cat for the decat pipe, did you notice any rattles or bits falling out of the catalyst? If the cat was breaking up, could that cause your symptoms? I just wonder, as the decat downpipe symptoms seem to be the only solid clue.....

 

If your boost gauge is a pneumatic device, if it tapped into the inlet manifold and correctly calibrated it will give an accurate indication of boost. If it reads 0.8bar then unless its stuck I'm not sure why you think you are intermittently running 0.5bar.

If you have tried an MBC and the problem remains it also indicates the problem may not be boost related as you have taken the solenoid out of the control circuit (the only thing remaining is the actuator, so you could check that for play).

If your IAM drops due to det you will feel a loss of power. If no more det is sensed it will rise again within a few miles. The IAM has to drop to very low values before it pulls boost (it will pull ignition then richen the AFRs first). I've seen cars with similar problems before, in most cases the daughterboard has resolved it indicating it was a management issue.

 

The boost gauge is the standard JDM wrx one above the stereo in the bank of 3 gauges. Its plumbed in via a T-piece from the manifold ( standard Subaru plumbing and pipes)

When I first used the MBC the boost gauge would always say 0.8/0.9 but occasionally you could feel that it was'nt boosting that much. One time it was saying 0.8 but it was slow so I quickly changed it back to the solonoid to control boost and it now said 0.5 on the gauge

everything bar the turbo and actuator has been changed....complete wing boost unit thingy, ECU, 3 solonoids, vacuum pipes, air flow meter, O2 sensor, plugs, coil packs, knock sensor. Ive lent a td04 from a wagon WRX that I might fit just to eliminate turbo/actuator from the equasion.

If it was any other car it would have been sold by now but I love it really and when its working it knocks the socks off my old celica GT4

 

Are you running a U8 ECU?

 

i didnt know jdm's had boost guages as standard...mine didnt as i had to fit em via a pillar mount

 

Its the standard ECU that the car came with, when I swapped it for one of a working 93wrx it did the same thing???

The boost gauge on the car is in a bank of 3 just above the stereo....I thought that the early imports came with these?

 

Would get rid of the VTA dump valve and go back to standard recirc dump valve do a search there have been lots of probs with these .

Mark

 

If boost gauge is reading what it should if things are correct and you are not getting the same results in the real world the, problem is a leak in the in- between of the two or there abouts? Mechanical(not electrical) gauges tend not play up.

 

Guys,

Ive had the bleed valve on the car for about a week now (actuator to compressor, by- passsing the solonoid and set up for a max of 0.8bar)
and so far so good..........

When I used the bleed valve last time I connected it to the actuator to the subaru compressor vacuum hose with the plastic reducer in and it did the 0.5bar thing

Ill get a proper boost controller on it as soon as ive forked out the cash for two new rear arches ........ahhh imports, don't you just love them. Bloody rust.

thanks for all your replies guys

 

I've done similar to you, that is I fitted a MBC, dawes type to fix a problem with the Boost Solenoid. Its been fitted for a good while now with no problems. In fact spool up is much improved. I've not set it any higher than my chip dictakes, so I can't see any problem in keeping it fitted indefinatly.

 

since iv had my esl chip fitted iv gone back to my original boost circuit(connected through boost solonoid pipework) However im missing my ealier spool up which i acheived with my hybrid dawes mbc...So me thinks it wont be long before i go back to using my mbc once again

 

Just thinking.......

If I get one of those ESL chips can I use my MBC or does it need to use to original boost system ie:solonoid and wing mounted stuff?