Problem Coming On Boost

[mad032]

I recently blew my intake manifold appart and have sine had it welded back together and i have fitted it and the car starts perfectly but when the turbo starts to spool it stutters and wont build up any boost even if i hold the pedal down it wont pick up. i know this isnt the greeatest description but i dont know how else to describe it.

Cheers Ryan

[Sandeep]

have you done a boost leak test?

[mad032]

yep i have been right over everything to do with vacume.

any ideas how to check a cooler fo blockages? i did find bits of rubber from a perrished wastegate vac line in the plenum.

[RBwhatever]

If there's a vac leak it'll hunt at idle.

If there's a boost leak, it'll lose boost and splutter and backfire and run rich, and just accelerate like a bogged down dog.

(I keep a copy of this so I don't have to type it everytime)

You can do a leak test.

What you'll have to do is,

1. take your pod and AFM off.

2. use a baked bean can (full) and put it into your rubber intake pipe (assuming its still the stock one).

3. tighten up the hose clamp onto the tin creating a seal.

4. Open the throttle body with a brick on the accelerator pedal, so you can read pressure on the boost gauge.

5. take a hose that is plumbed into your intake between the turbo and the plenum or off the plenum itself.

6. Get an air compressor and pressurize the system through the hose and get someone to read the psi on the boost gauge. you only need about 5psi. you can use the compressors at the servos.

7. Listen for a leak. And use the soapy water in the spray bottle to find exactly where it is if need be.

It is easier to find a boost or pressure leak using this method because the car is not running and is easier to hear and locate.

[mad032]

Thanks mate i will see how i go. You say that it will cough and splutter carry on but berfore boost will it drive ok? mine is fine off boost asin accelarating up to 4k

[RBwhatever]

Yeah it runs fine off boost till 4000 odd rpm or so. Its when there's enough boost to open up whatever(usually a intercooler join) it is and leak out pressure.

Boost bleeds off and it runs rich and just feels like it doesn't want to accelerate.

If you've touched you IC piping recently, then there's a good chance the piping connections aren't on properly or weren't done up tight enough, so it blows open under boost. Otherwise a joiner may have a split in it.

[mad032]

positive that the plumbing is good, we have come up with another theory, that maybe the fuel pressure reg isnt working becoz its possibly leaning out as it comes on boost. We did a bit of a test today and if i let the revs creep up slowly to 4500k then give it a bit it isnt as bad but if i nail it at 3k and let it try and wind up it hates it. Any thoughts on this.?

by the way the pump is all good as it is a 5.7ltr pump and yet to check the filter

Edited November 6, 2007 by mad032

[RBwhatever]

Your fuel reg can still be good.

You say you have a 5.7L pump, is that from like an SS commy with an LS1?

Your pump might not be up to scratch. It might not be able to keep under a sudden demand. Ah I dunno

[chrisd1]

check intercooler as stated, also AFM, if that fails, it sound slike fueling problem...

[bubba]

I thought those genIII pumps were notoriously dodgy.. at least that's what I've heard from my mates with SS utes.