[andykao]

So my OG 9-3 is stuck at base boost (i guess), there's not too much power when i floor it and the turbo gauge will only go halfway.


When i got the car, it was stuck at base boost - diagnosed a bad BPC valve, changed it with a new one and i got full boost.

MAF was cleaned about 2 months ago, also change the DIC with a new one, spark plugs and also new vacuum hoses. Boost was fine, i had full boost, but didn't drive the car too hard for a while (only city driving). Last weekend, when i tried to drive it hard but it won't boost.


I tested the BPC and it's ok (shows 7 OHM resistance as it should and the air passes through it as it should). Also removed the hose from the wastegate to see if that works and it boosted into the red, hitting fuel cut. So i guess the wastegate works fine. I also tried resetting the ECU (pulled battery for about 24 hrs, pressed the brake pedal). Nothing works.


I won't know what to try next or what should i look for. I don't have open sid, ordered a USB cable (obdlink) a few days ago, still waiting for it to arrive. I have a bluetooth reader, i connected to the ecu and i don't get any codes or anything else. The car runs fine, idle is fine.


Any input would be appreciated.

 

[Mort]

Don't forget if you have an auto - boost is limited in the first and I think second gears. Not 100% sure about manual versions. But I'm guessing you already know this, about boost levels in gears etc.

 

[jakejm79]

Mort is right and boost is also limited in 1st and 2nd with a manual. Actually if the ECU is unable to figure out what gear it is in (often due to ABS sensor/module problems) you will get base boost only - though often the ABS warning light or CEL would be on.

 

[andykao]

no warning lights, no codes, even tried the bolt mod - still the same thing. car's a manual, i used to get almost full boost in 2nd.


does anyone know a good way to test the BPC valve? It shows 7 ohms resistance and i can blow through it, but i'm not 100% sure it works properly...

 

[mr rx-7 tt]

How do you know if the MAF is bad and how did you clean it?

 

[wulff2210]

Hi my OG 9-3 aero will only hit base boost, and i tried pulling wastegste hose off the bpc, does it mean my wastegate is bad?

 

[Mort]

Hi Wulff, There could be a number of reasons why you are getting limited boost. Is your 9-3 Aero a manual or AT?
Remember you only get limited boost in 1st and 2nd. It would be a good idea to check your vacuum lines, and if you have an ODB2 reader check for any error codes. Failing that - There are some standard checks people run through. I think the 'Bolt' method is the most talked about.

 

[wulff2210]

Hi Wulff, There could be a number of reasons why you are getting limited boost. Is your 9-3 Aero a manual or AT?
Remember you only get limited boost in 1st and 2nd. It would be a good idea to check your vacuum lines, and if you have an ODB2 reader check for any error codes. Failing that - There are some standard checks people run through. I think the 'Bolt' method is the most talked about.

Its a manual im getting limited boost in 3rd too, and i did check the vaccum Lines and replaced a bad one, i did Also replace the bpc valve

 

[BobSaabit]

Wuff: Are you saying that you pulled the hose off the wastegate and it stayed at bast boost? With the hose off, the ECU is out of the picture in terms of controlling boost. It would tend to indicate a wastegate issue, although a significant tuning issue could also just make engine performance bad and unable to get to boost.

Does the wastegate move if you grab it and try to move the rod back and forth? It should be closed when the engine is off or at idle. I'll ask the standard question about "have you replaced the vac lines; is the DIC good; are the plugs fresh and gapped .9mm, was it running well previously", but the next thing I would be doing is pulling the downpipe off at the turbo and visually checking the wastegate operation.

Three nuts, the top two are not bad, the bottom one is a real PITA (13mm or 1/2" very short arm wrench needed, or maybe a fine tootl ratcheting open or box end). A small MAPP gas torch will help a lot with all of those if they've never been off and/or some penetrating oil, or the parrafin trick, etc. You might want to to undo the clamp (a bolted bar underneath on the downpipe, bottom side detach) to move the pipe off the turbo.

 

[wulff2210]

Wuff: Are you saying that you pulled the hose off the wastegate and it stayed at bast boost? With the hose off, the ECU is out of the picture in terms of controlling boost. It would tend to indicate a wastegate issue, although a significant tuning issue could also just make engine performance bad and unable to get to boost.

Does the wastegate move if you grab it and try to move the rod back and forth? It should be closed when the engine is off or at idle. I'll ask the standard question about "have you replaced the vac lines; is the DIC good; are the plugs fresh and gapped .9mm, was it running well previously", but the next thing I would be doing is pulling the downpipe off at the turbo and visually checking the wastegate operation.

Three nuts, the top two are not bad, the bottom one is a real PITA (13mm or 1/2" very short arm wrench needed, or maybe a fine tootl ratcheting open or box end). A small MAPP gas torch will help a lot with all of those if they've never been off and/or some penetrating oil, or the parrafin trick, etc. You might want to to undo the clamp (a bolted bar underneath on the downpipe, bottom side detach) to move the pipe off the turbo.

Yeah i can move the lever on the wastegate, i just replaced the spark plugs and the car deffinetly runs smoother but it didnt fix the boost issue. Just tried the bolt mod it didnt do anything (maybe a little improvement in low end torque). Maybe i Should try removing the downpipe next?

 

[wulff2210]

Yeah i can move the lever on the wastegate, i just replaced the spark plugs and the car deffinetly runs smoother but it didnt fix the boost issue. Just tried the bolt mod it didnt do anything (maybe a little improvement in low end torque). Maybe i Should try removing the downpipe next?

Wuff: Are you saying that you pulled the hose off the wastegate and it stayed at bast boost? With the hose off, the ECU is out of the picture in terms of controlling boost. It would tend to indicate a wastegate issue, although a significant tuning issue could also just make engine performance bad and unable to get to boost.

Does the wastegate move if you grab it and try to move the rod back and forth? It should be closed when the engine is off or at idle. I'll ask the standard question about "have you replaced the vac lines; is the DIC good; are the plugs fresh and gapped .9mm, was it running well previously", but the next thing I would be doing is pulling the downpipe off at the turbo and visually checking the wastegate operation.

Three nuts, the top two are not bad, the bottom one is a real PITA (13mm or 1/2" very short arm wrench needed, or maybe a fine tootl ratcheting open or box end). A small MAPP gas torch will help a lot with all of those if they've never been off and/or some penetrating oil, or the parrafin trick, etc. You might want to to undo the clamp (a bolted bar underneath on the downpipe, bottom side detach) to move the pipe off the turbo.

And yes i pulled the wastegate hose off of the bpc valve

 

[jvanabra]

Are you positive you are removing the correct host from the solenoid? IMO, the "bolt mod" is the good answer here, since it prevents a boost/vacuum leak which could introduce other issues.

 

[Mimmi]

Have you checked that wastegate rod is connected to WG?

 

[wulff2210]

Are you positive you are removing the correct host from the solenoid? IMO, the "bolt mod" is the good answer here, since it prevents a boost/vacuum leak which could introduce other issues.

yeah, im pretty sure it was the correct hose it even had a W on it

 

[wulff2210]

Have you checked that wastegate rod is connected to WG?

not exactely, but when moving the rod i could definetly feel the tension increasing

 

[jvanabra]

yeah, im pretty sure it was the correct hose it even had a W on it

I wouldn't 100% count on that - someone could have put them back in the wrong place. I would trace W to its destination, which should be the wastegate actuator.

But, truly, you should disconnect the C hose (verify it ends on the Compressor housing) and zip tie a screw into it. That way you aren't introducing an air leak, which could be damaging to the engine or turbo. All you're doing is preventing intake pressure from acting on the wastegate actuator so it remains at rest. Be aware you will have uncontrolled boost, so be gentle on the go pedal.

If you still show low boost, you have an air leak somewhere (external, or into the evap system, etc.), some element of the turbo is damaged, or (really unlikely) a serious engine running issue.

Edit: If you have a Mityvac you can do a pretty good test on the WGA - put the Mityvac into the W line, and make sure it holds both pressure and vacuum. Under pressure, you should see the wastegate rod & swing valve move (and stay put under constant pressure).

 

[wulff2210]

I wouldn't 100% count on that - someone could have put them back in the wrong place. I would trace W to its destination, which should be the wastegate actuator.

But, truly, you should disconnect the C hose (verify it ends on the Compressor housing) and zip tie a screw into it. That way you aren't introducing an air leak, which could be damaging to the engine or turbo. All you're doing is preventing intake pressure from acting on the wastegate actuator so it remains at rest. Be aware you will have uncontrolled boost, so be gentle on the go pedal.

If you still show low boost, you have an air leak somewhere (external, or into the evap system, etc.), some element of the turbo is damaged, or (really unlikely) a serious engine running issue.

Edit: If you have a Mityvac you can do a pretty good test on the WGA - put the Mityvac into the W line, and make sure it holds both pretty and vacuum. Under pressure, you should see the wastegate rod & swing valve move (and stay put under constant pressure).

okay, i will try plugging the C with a screw. When doing this should i just keep the bolt mod on the car aswell?

 

[jvanabra]

I like one test at a time, but no, they shouldn't interfere with each other.

 

[wulff2210]

I like one test at a time, but no, they shouldn't interfere with each other.

I tried pluging the C and still had low boost

 

[jvanabra]

Then you're probably into a turbo issue (like a wastegate problem), maybe a clogged exhaust, or some sort of deeper engine issue. An engine issue is a real stretch as you'd likely have CELs if something was that messed up, but still on the table. I'd start with a Mityvac test of the WGA as above.