Low Boost Problem

[rs200]

first sign of problem was ... in one second boost gauge rise to -0.5 before was -0,8 on idle...

it was strange to me but, car go well , few days pressure didn't drop to -0.8 (still 0.5) and now came boost problem...

one more strange thing is that digital boost gauge in dash is always around 0.5 ,0.6, 0.7. even when go to boost.

my secondary boost gauge is on 1.5 bar but on dash 0.7 - in this rear moments engine go well.

what part of engine give information to boost gauge on dash?

[newsh]

I think maybe you have a leak in the boost line to the ECU. Dash guage gets its signal from ECU..

[rs200]

I check all boost line on car... before 8 month I put all new boost line.

the problem is in that engine in one moment have boost and in the nother not ,0.2 bar of boost:corey:


any advice???

[rs200]

now I have problem with other 200 20v (stock)...

well they can't produce more than 0.4 bar

NO fault codes
NO boost leak
GOOD N75
GOOD MAF
ALL air pipes are new and good
NEW BOV
perfect ECU 100% OK
wastegate OK


they want to produce 1bar if I block pipe which go to waste gate , but then comes a fuel cut...

what can cause that problem? only 0.4bar???? why?
please help ... HELP...

[prj]

Do output test of N75.
Pressure test intake.
Pressure test intake with bypass return disconnected.

[rs200]

N75 have 32.2 ohm , and thew work ok... 100% sure. and 100% OK.

I done boost leak test and all ok. they hold 1bar with no problem. if I understand you , you sad that I do boost leak test with disconected BOV?

thanks Dmitry

[prj]

Is it a BOV or a bypass?
And you don't test N75 resistance, that's fairly useless. Do output test in vagcom.

[rs200]

I dont have VAG COM... I know that is a problem.

but I put my N75 from my car which are 100% OK... and it have same problem...

isn't BOV or bypass the same thing? BOV are NEW.

[prj]

No...
A BOV vents to atmosphere, a Bypass recirculates air back in front of the turbo.

If you don't have vag com, stop wasting time
Probably there is a code/intermittent code in the ECU.

[rs200]

so you wan't to say that VAG COM can detected something that blink code can't ?

if I put the car on blink code - they give me 4444 - no fault code detected...


OK.. than it have NEW bypass

[prj]

Yes, but you can not do N75 output test.
It does not have to be the n75 itself, it can be the wiring.

[rs200]

I check all wiring from N75 to ECU and fuse box, whole electric circle are good.. everithing is perfect..

[prj]

If your car was perfect, then ECU would not be in limp mode.
Either that, or there is no signal going to N75.
Do an output test and you will know.

If the wire has 1 or 2 strands connected and the rest broken, then resistance will be still close to 0, because the current of the tester is very low. But N75 won't work.

[rs200]

the problem is not N75 or something conected with him...

all wires are good and N75 do "klik" when I disconect him , and one more time "klik" when I conect him.

what else can produce this issue of low boost?

thanks Dmitri for help, you are always here when I need something, or have some problem... for me you have special place on that forum. but N75 is not a problem it this case..

[prj]

Clean TPS connector.
But you should have a code, if it was TPS.

If all else fails, take a digital oscilloscope (USB scopes are not very expensive) and monitor N75 duty.
You will then easily see if the issue is because ECU is in limp mode, or there is some other fault.