No Boost at all....need help

[andyg plym]

my homefry aby coupe is not boosting at all, it is also driving very badly. boost gauge stays in the minus section all the time
will idle at minus 8 bar then when drivin only rise to 0 bar before boost cut cuts in, idles very badly too (isv swapped and known to be working). dont even get mecanical 0.4 boost when wgfv dis connected, stays under 1 bar!

today merlin (thanks for the help mate) put a code reader on and came up with no relevent codes. we manaed to do a pressure test and couldnt find any obvious air leaks although we only went upto 0.5 bar (boost guage registered 0.5)

checked already:

all vacuum pipes replaced (all way back to ecu)
intercooler - mark h mod fitted
maf fine (taken out my avant and no fault codes given)
wastgeate freed up and working fine
ecu map sensor
wgfv swapped for known working unit


got a larger zorst manifold on (in prep for rs2 turbo)
and stock k24, recirc valve is plumbed in the bottom hose by intercooler (tried reverse orientation too - no better) and the port that vents back to maf is left open (souldnt make a difference to holding boost?)Maf moved to pressure side (not my choice but it worked on car before i had it)

you can hear air escaping when driving,then it misfires badly, not like a vaccum hose leak,its more serious then that.
Also on idle car only revvs to 5000rpm and wont go above.Checked throttle body hose and seems fine no cracks or splits.

is there anythin else to try?

[k.alle]

Have you had a look at the cats?

If they collapse you'll get close to no boost and wont rev high at all.

[andyg plym]

3" zorst turbo back no cats just 1 backbox

[k.alle]

Oh I see... your issue sounds tricky to say the least!

[andyg plym]

i know! its really upsettin me!

[frazz]

Alrite Mate,
What about the inlet manifold gasket, if its leaking it will suck in to much air and make it run like a bag of crap, try abit of carb cleaner or brake cleaner while its running if the engine note changes, its leaking

[Jamo]

The port that vents to maf is open????????

Are you saying your PCV system is open as this would be an air leak

[andyg plym]

yes jamo open, previous owner put breather on rocker cover end pipe. no maf pipe at all

[newsh]

If the PCV is disconnected make sure the pipe underneath the inlet manifold, near the throttle body, is capped off, its a smallish pipe maybe 6 or 8mm bore that normally goes to the PCV system via a one way valve and the carbon can valve. Also make sure the 20mm one on the side of the MAF hose is blanked off too.

[andyg plym]

i wondered about that one,is that the one that goes to a blue sensor? i read an old post of yours newsh saying how pcv needs to be blanked

[merlin's S4]

If the PCV is disconnected make sure the pipe underneath the inlet manifold, near the throttle body, is capped off, its a smallish pipe maybe 6 or 8mm bore that normally goes to the PCV system via a one way valve and the carbon can valve. Also make sure the 20mm one on the side of the MAF hose is blanked off too.

Should have thought about this earlier! Makes perfect sense with the symptoms we were getting earlier. Not only will this leak but it will also allow unmetered air in on vacuum.

[andyg plym]

just blancked it off......will report later bit akward,covered in cuts....

[s2_bo]

Good luck Andy, hope this solves it although i doubt it somehow..


P.s. have you check that the ECU is ok?

[andyg plym]

blocked off pipe, still no difference. ecu was opened yesterday,cecked small pipe and fine,nowt loose.


any more ideas peeps?

[220bhp]

My guess is one of two things, I have had this problem twice ,first time it was the front knock sensor , second time it was the MFTS.
My car is a 3b, hope this helps,