Turbo Pulsing

[jwbailey05]

Hey I have just gotten a 2004 WRX from my uncle. It runs great except
the turbo constantly pulses. It is most noticeable driving at a
constant speed and then slowly accelerating over 3 thousand rpms. It
sounds like maybe the waste gates are letting air our prematurely but
I have had a few people look at it and they can't seem to find
anything wrong. My uncle had some after market modifications done to
it including some exhaust work, and a new up-pipe and down-pipe along
with a GReddy system installed. I have heard that the GReddy doesn't
work well on that year of WRX and have recently uninstalled it and put
in a stage 2 engine management system in it. I think the problem has
to be mechanical because the turbo still pulses with the management on
or off. If you have any ideas or further questions please let me
know. I would really appreciate it. Thanks a lot.

 

[Mk IV]

(e-mail address removed) scribbled:

Hey I have just gotten a 2004 WRX from my uncle. It runs great except
the turbo constantly pulses.

What exactly do you mean by 'pulsing'? You hear it? Feel it?

 

[Joe]

(e-mail address removed) scribbled:


What exactly do you mean by 'pulsing'? You hear it? Feel it?

You hear it and feel it. I can hear the air going into the turbo but
then being let out too soon followed by air going back into it. It
will do that a number of times even when my foot is accelerating at a
constant rate. You can feel it by being pushed back into your seat
and then not being pushed back into your seat almost like I was
pushing the gas and the letting off and then pushing and letting off.
I hope that helps. I know the descriptions may be a little tuff to
understand. If you would like me to try to describe it better please
let me know.

 

[Mike]

Do you have a boost gauge on it (if not put one on its a easy job) - does
the pressure stay constant or does the pressure surge during the symptoms.
What pressure is the turbo producing?
Does it have an aftermarket blow of valve?, some require adjustment that
could result in the symptoms you describe. If you do, disconnect the small
vacuum hose to it does the problem persist?
Cheers
Mike

 

[Joe]

Do you have a boost gauge on it (if not put one on its a easy job) - does
the pressure stay constant or does the pressure surge during the symptoms.
What pressure is the turbo producing?
Does it have an aftermarket blow of valve?, some require adjustment that
could result in the symptoms you describe. If you do, disconnect the small
vacuum hose to it does the problem persist?
Cheers
Mike

I don't have a boost gauge but I do have an access port that lets me
read how much psi is being given from the boost. I ran it on the
interstate at the boost is surging and dropping by about 4psi every
time it pulses. It does have an after market blow off valve. Its a
GReedy. I think I am going to get rid of that and go back to a stock
04 valve because I have been told by a few people the GReedy boost
control isn't good on the 04 model. Have you heard anything about
that?
Thanks
Joe

 

[Joe]

I don't have a boost gauge but I do have an access port that lets me read how much psi is being given from the boost. I ran it on the interstate at the boost is surging and dropping by about 4psi every time it pulses. It does have an after market blow off valve. Its a GReedy. I think I am going to get rid of that and go back to a stock 04 valve because I have been told by a few people the GReedy boost control isn't good on the 04 model. Have you heard anything about that?

Thanks
Joe

 

[Mike]

What is the maximum boost pressure you are getting?
Mike

 

[Joe]

I can get up to 17psi maximum but once the pulsing starts is will drop
down to 13 or so and then back up.

 

[Mike]

Hi
If you want to know if the electronics are the culprate then there is one
test you can do the will eliminate them.
disconnect the vacuum hose conected to the wastegate.
BE AWEAR ONCE YOU DO THIS THE COMPUTER CAN NO LONGER CONTROL BOOST PRESSURE!
and this is also the reason to do this. It also requires the driver to
control bosst pressure with the throttle.
Try to fight the temptation to see how high the boost presure will go, it'll
probably exceed 20PSI
The computer does have one last resort to prevent overboosting & that is to
cut the fuel but its best to avoid this.
If the surging stops then the problem was most likly electrical, maybe a
faulty air temperture sensor or boost pressure sensor or solinoide valve
controlling the waste gate. There is one other possibility that I just
thought of & that is the ECU is detecting detonation, what otane fuel are
you using?
If the problem continues then its most like something on the inlet side
leaking air like the blow-off valve or impingin airflow like a clogged
filter or obstruction.

 

[Joe]

Thanks a lot, ill try that and then let you know how it goes.

Thanks
Joe