Problem with version 7 STi boost control

[ben-jamminn]

Put a boost gauge in my new car today, I\'d been wondering why it seemed sluggish and I now see it\'s only reaching 0.5 bar max boost (which I assume is wastegate pressure?)

I checked line between compressor and the \'tee\' to the wastegate actuator and the restrictor pill seems to be there.

Next i removed the vac line to the wastegate actuator, drove down the road and proved that it\'s not a mechanical/turbo issue as the boost went past 0.5 (took foot off gas at 1 bar as I guess the pressure would have kept rising to whatever the turbo is capable of flowing)

I guess that only leaves the boost control solenoid, is there a way of testing the function of it?

Another thought I just had, when I got the car it would hesitate a bit between 2nd and 3rd gear but after cleaning the MAF sensor this has gone away, could it be that the ECU has \'shut off\' the BCS due to the dirty MAF, and needs to be reset?

Hope someone can help

Ben

[G-unit]

0.5bar is limp mode so try a ecu reset and check codes

[ben-jamminn]

New age Impreza\'s don\'t have the plugs under the steering column do they?

I disconnected battery for a few mins, took for a drive and boost is back to (what I assume) is normal, 1.1 - 1.2 bar

Should be interesting to see if it reverts back to limp mode..

It was a re possessed car so it would have spent a while in the impound yard then a while at turners etc, maybe the fuel had gone a bit bad or the muppets had put 91 in it, causing det, which is why it\'s gone into safe mode?

Ah well I\'ll see how it goes over the next day or too

[ben-jamminn]

To update;

Hasn\'t gone back to limp mode, but boost doesn\'t come on very smooth, car seems to bog down a bit around 0.5 bar, almost feels like the brakes are coming on! i.e boost is still increasing but feels like car is slowing down? then it suddenly spikes up to 1.2 really fast.

So far I\'ve:

Cleaned MAF sensor

Replaced air filter

Reset ECU (well, unplugged battery for 10 mins, I hope that resets it..)

Replaced spark plugs

I hope some of you knowledgeable people can help!

Ben

[Guest]

Just disconnecting the battery may do it but when its off hold the brakes on for 20 seconds it will completely drain the power out of the system.

[ADIKT]

I think you need to disconnect battery and press brake peddle in to reset ecu correctly

Edit #tooslow

[ben-jamminn]

boost lines seem to be correct, pill is on the compressor side of the waste gate tee, How do I test the solenoid?

[Pappu1]

As a quick test maybe borrow a Tap and set it to say 18-19psi an see if that makes a difference in the way boost comes at all

Also any exhaust leaks

How is the condition of the turbo intake pipe any leaks there

Air filter?

What Bov?

[chappell943]

Sounds like the ECU is disabling boost control because of det, if someone in your area has a tactrix cable then you could plug the car in and easily find out if its an ecu issue or faulty solenoid etc.

[ben-jamminn]

Had the ECU scanned today, no codes. Kinda gutted I was hoping it would have found something.

My mate that scanned it reckons it\'s a missfire, need to establish whether its spark or fuel related

[ben-jamminn]

OK thanks, thats something to consider trying

[Marky]

Close gap up on / replace the plugs (does no harm to do with a new car anyway), also try it (as has been said) with a boost tap and see if problem persists

If problem goes away with tap: ECU or boost solenoid problem (either ECU is retarding boost due to knock or mystery problem, or solenoid is sticking closed)

If problem stays: Not either of those look towards misfire / something else at fault

Trial by elimination

[ben-jamminn]

Plugs are new, I replaced them last weekend with NGK Platinum\'s

Yeah I need to try and find a tap, any of you other Christchurch guys have one?

Thanks

[Marky]

Bunnings - outdoor irrigation section - 50c for an adjustable nozzle piece hahaha

On a more serious note I\'ll have a look round the garage

[ben-jamminn]

hahaha reckon I could set up a sprinkler while I\'m at it?

Ok thanks!

[ben-jamminn]

Still haven\'t tracked down a manual controller yet but I did drive to Ashburton on the weekend, which was the first open road drive I\'ve had on the car.

On passing lanes etc, I noticed the boost fluctuating, hitting peak around 1.2 bar then dropping back to 0.5 then back to 1.2 again, this cycle would continue until i let my foot off the accelerator. All the while the car was surging with each onset of boost, although the RPM remained constant. This also happened in all gears. I think this is the symptom I was seeing earlier (boost hitting peak then dropping right off) only on the open road I was on boost long enough to see the pattern re occur, rather than around town where you can\'t stay on boost as long.

So fluctuation, I take it the wastegate must be opening and closing? I\'ve pulled off the BCS, connected it to 12v and it clicks as it should, I read on an american forum that connecting the 2 green plugs under the steering column puts the car into \'test mode\' and cycles all the sensors, I did this but was just getting constant power at the BCS, is this right? The american forum said it should cycle..

This problem is so frustrating! an STi should be a pleasure to drive but at the moment it\'s just a pain in the ass haha

[chappell943]

Just saw you were in Christchurch, I have a gfb atomic boost tee if you want to try it out and see if that fixes the issue? I also have a tactrix cable and I could check if there are any memorized codes (even if no cel).

[ben-jamminn]

OK cool! I\'ll PM you

Cheers

[Pappu1]

 chappell943 said:

Just saw you were in Christchurch, I have a gfb atomic boost tee if you want to try it out and see if that fixes the issue? I also have a tactrix cable and I could check if there are any memorized codes (even if no cel).

had to be said - this guy is a legend!!!!

yea that tap ought to sort boost and decide what the matter is...

[boon]

Dodgy BCS seems somewhat likely to me...

[ben-jamminn]

Yeah that\'s what symptoms point to although I removed it and tested with flying leads off the battery and it cycled (clicked)

What else goes wrong with them? Does the shuttle itself start leaking or bypassing?

[boon]

 ben-jamminn said:

Yeah that\'s what symptoms point to although I removed it and tested with flying leads off the battery and it cycled (clicked)

What else goes wrong with them? Does the shuttle itself start leaking or bypassing?

As I understand it the solenoid is triggered in order to build boost i.e the duty cycle increases to keep the wastegate shut by allowing the boost from the feed nipple on the turbo to bleed to the intake instead of pressing on the wastegate actuator. If the BCS can\'t keep up with the duty cycle required I believe it\'s designed to fail shut so that in a failure situation you\'ll get wastegate pressure instead of freeboosting.

[ben-jamminn]

Thanks to Chappell943, he lent me a GFB manual boost controller fitted and set to 1 bar and now the boost fluctuations have gone ;D

However I still have the surge/hesitation at part throttle as boost starts to build (0.5 bar approx) i.e speeding up to merge into traffic, accelerating out of roundabouts etc..

I\'m thinking misfire? (although plugs were replaced 3 weeks ago)

Is it possible that the factory BCS was going mental because of the miss (causing the boost fluctuations) and now that the BCS is bypassed the boost is remaining constant although the miss still remains?

Happy to hear your thoughts..

Ben

[Marky]

Misfire maybe (just gap the plugs tighter, have a look and see if one looks different to the others while you\'re there), AFM fault also maybe, intake leak maybe

The factory boost control isn\'t closed loop - the car doesn\'t monitor and change the BCS frequency to maintain a certain PSI level - it either pulses if things are happy, or as has been said just does nothing as a fail safe to drop boost if there is anything bad going on (like CEL sort of issues that the car actually knows about) - though a bad miss could sound like wicked knock and make it pull boost (I don\'t know if subys do this as a last resort?)

Does boost sit dead level when this hesitation occurs, or does it flicker (hard to spot tho) - if it still has the factory exhaust it\'s hard to hear if it\'s a misfire I guess

[titian]

 ben-jamminn said:

Thanks to Chappell943, he lent me a GFB manual boost controller fitted and set to 1 bar and now the boost fluctuations have gone ;D

However I still have the surge/hesitation at part throttle as boost starts to build (0.5 bar approx) i.e speeding up to merge into traffic, accelerating out of roundabouts etc..

I\'m thinking misfire? (although plugs were replaced 3 weeks ago)

Is it possible that the factory BCS was going mental because of the miss (causing the boost fluctuations) and now that the BCS is bypassed the boost is remaining constant although the miss still remains?

Happy to hear your thoughts..

Ben

Could be your knock sensor...Despite no code...They can cause this surging/power loss / missing ;)

http://www.clubsub.org.nz/forum/index.php/topic,33060.0.html

Couild be ;D