Boost Issues?

[mmcd87]

Hi,

The peak boost level on my '05 WRX PPP has never really been consistent in that sometimes it would hit it, sometimes it wouldn't and lately it seems to be getting slightly less than usual... The car typically used to hit 1.2 bar, occasionally 1.25 bar in the higher gears, but its more like 1.15 recently.

Fuel hasn't changed (Tesco 99) and it still seems to drive fine otherwise - I'd have thought I'd be getting more boost in the colder months if anything! I'm reading this off the OEM Lamco boost gauge, which also seems to be working as it should.

The cars fully serviced with only 30k miles. I've tried an ECU reset with the same results.

Any help appreciated.

Thanks in advance.

[fildigger]

Vacuum leak!!

[stuzzer]

try cleaning the boost control solenoid by the drivers side front strut. The more gunk you have in there the more erratic the boost will be. A quick squirt of brake/carb cleaner through it should clear it out.

[ScoobieWRX]

Sounds like two good bits of advice... Check for Boost/Vacuum leaks, EBCS cleanout.

If the above doesn't work then you could be looking at something a bit more serious like a failing EBCS or MAF sensor.

If the EBCS is failing then rather than pay for another OEM 2-port get yourself a Prodrive or Perrin 3-port EBCS for similar money but your engine will need some remapping to compensate for the overboost you'll get as a result. Don't get a 2nd hand 2-pot EBCS when new 3-ports are very reasonable money.

Difficult to diagnose a MAF that's only just starting to fail but as it gets worse your car starts to run differently/rough at times, stumbling, erratic/oscillating cruise at low revs, dodgy idling, boosting issues etc...

My guess is the advice you've already had should hopefully sort it.

[mmcd87]

Thanks for the help. Seems a lot flatter today (not much over 1 bar...) at that was at -2degC.

Is there any more likely hoses I should be looking at? The car 'seems' to drive/idle/start/stop fine otherwise. I cleaned the boost solenoid around a year ago but I guess I should look at it again.

[ScoobieWRX]

If you don't clean your boost controller out but once a year i don't hold much hope out for your MAF sensor either. I suggest you take it out and have a look at that too.

I bet the resin covered sensor is absolutely covered and caked in black crap. Use brake cleaner like holts and spray it on to the sensor. The pressure from the jet of solvent alone should be enough to get the crap off and leave the sensor sparkling without touching it.

Brake cleaner evaporates very quickly so shouldn't leave any residue behind. That may well be the answer to your current woes.

[mmcd87]

ScoobieWRX said:

If you don't clean your boost controller out but once a year i don't hold much hope out for your MAF sensor either. I suggest you take it out and have a look at that too.

I bet the resin covered sensor is absolutely covered and caked in black crap. Use brake cleaner like holts and spray it on to the sensor. The pressure from the jet of solvent alone should be enough to get the crap off and leave the sensor sparkling without touching it.

Brake cleaner evaporates very quickly so shouldn't leave any residue behind. That may well be the answer to your current woes.

I cleaned the MAF when I cleaned the solenoid. Both were fine. I've only done under 10k miles since then but I take your comment on board. I've got a K&N panel filter in it so probably worth checking the MAF for that now you've mentioned it.

[mmcd87]

Update. I've cleaned the MAF and although slightly smoother the performance is still not completely there. I'll try the EBCS at the weekend. Anything else worth looking at? Thanks

[ScoobieWRX]

Hoses/piping to check:

• Turbo to intercooler
• Intercooler to throttle body
• EBCS to Turbo Inlet vacuum hose
• EBCS to Turbo (including T-Junction vacuum hose containing restrictor pill)
• Inlet manifold to head joins (where you can)

The best way to check these is to get a spray bottle with a weak solution of soapy water, spray all the joins and watch for bubbles when you manually (via throttle on throttle body) rev the engine to induce a little positive pressure and Air Bypass Valve (BOV) actuation.

You'll soon see if you have any boost leaks. I'm about to make up an apparatus to use on customer cars that uses compressed air to fill the whole induction system with air under pressure specifically to check for boost leaks. Saves having do it with engine rpms which isn't ideal.

Are you using a bog standard TMIC with the standard OEM BOV?

If not it could be that your aftermarket BOV has a weak spring or is not adjusted up far enough if adjustable. Very common issue with a lot of aftermarket BOVs.

If you have to the standard BOV can be easily modified to run with an FMIC in non-recirculated configuration and is the only one i would recommend to use unless you're running big power.

I hate aftermarket BOV's and they can cause so many issues.

ETA: It's a shame you're so far away otherwise i would get you to pop over here and let me plug in to see if there is anything untoward going on that would flag up on the laptop. I'm in Scotland weekend of the 24th Feb if you're anywhere near or can get to Pitlochry, if that's any help.

Edited by ScoobieWRX on Friday 10th February 14:31

[mmcd87]

ScoobieWRX said:

Hoses/piping to check:

• Turbo to intercooler
• Intercooler to throttle body
• EBCS to Turbo Inlet vacuum hose
• EBCS to Turbo (including T-Junction vacuum hose containing restrictor pill)
• Inlet manifold to head joins (where you can)

The best way to check these is to get a spray bottle with a weak solution of soapy water, spray all the joins and watch for bubbles when you manually (via throttle on throttle body) rev the engine to induce a little positive pressure and Air Bypass Valve (BOV) actuation.

You'll soon see if you have any boost leaks. I'm about to make up an apparatus to use on customer cars that uses compressed air to fill the whole induction system with air under pressure specifically to check for boost leaks. Saves having do it with engine rpms which isn't ideal.

Are you using a bog standard TMIC with the standard OEM BOV?

ETA: It's a shame you're so far away otherwise i would get you to pop over here and let me plug in to see if there is anything untoward going on that would flag up on the laptop. I'm in Scotland weekend of the 24th Feb if you're anywhere near or can get to Pitlochry, if that's any help.

Thanks for the tips - I'll give them a go.

And thanks for the offer regarding the diagnostics but it's a bit far south for me. I've plugged the car into ecuExplorer and no fault codes are displayed. Might look into the readouts a bit more to see if anything can be read from them.