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Discussion Starter #1
Hi can anyone tell me what the boost preassure is for a standard 1996 1.8t 150bhp motor,only getting 5psi now and severe power loss,reluctant to rev obove 4k,will however rev higher if you hold it ,turbo can be heard to spool up but has no affect on performance,any help on this would be much appreciated.
P.s there are no codes in the memory
Thanks
 

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I've had a LOT of trouble with my vacuum lines; I've found one broken vacuum hose or broken one-way-valve after another. You should definitely look into this.

Also, replace your Diverter valve; don't even bother checking if it's broken, because the stock DV is a piece of crap to start with. Go with a Forge or a HyperBoost; they're both very good and neither is made of plastic like the stock valve is.

EDIT: I'd bet money that your DV is broken anyway, because if the turbo spools but no power increase is felt, the prime culprit is a DV that's stuck in "blow-off" mode.
 

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Discussion Starter #5
can the missing 2 psi really make all the difference ,as the car feels like its only got about 90-100 hp max ,really slow and reluctant to rev obove 4k!
 

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1.8taeb said:
... only getting 5 psi at the moment.
Car is flat,reluctant to rev over 4k (will red line if you hold it) ,no missfires and no codes ,bought car as project with cam chain tensioner fault and worn cam bearing on one inlet bearing journal.
Fitted S/H cyl head (stripped/ground in all valves) new tensioner ect ,car starts and runs smooth just has lack of power ,seems like air mass fault ,but changed that ,made no difference ,one thing i did notice when i had VAG 1551 was fuel adaption keeps rising,only way to reset is to disconect ECU ,when re started rises up again,also exhaust fumes smell eggy ,am thinking too rich ?
Any help on this would be much appreciated...
Like Dan said, boost pressure should be 7 lbs on an AEB.

Please give more detail on rising fuel trims:
What are the values?
It "keeps rising" how high?
When you say rising, I assume you mean going positive - or are they increasing in the negative direction?

Increasing positive trim means that the O2 sensors *think* you are running too lean, so the trims increase beyond normal to compensate.

Somebody double-check my logic here:

I believe you may have a major boost/vacuum leak. Under no boost (closed-loop operation), it turns into a vacuum leak. A vacuum leak introduces unmetered air into the system. This causes the O2 sensor to read "lean," so the fuel trims go positive to compensate (because of the closed-loop feedback).

The leak is post-turbo-outlet, so it turns into a boost leak under boost, so you don't get full boost, and it runs rich, but you're open-loop so there's no feedback and the trims don't compensate, so it stinks and has no power, not only because the boost is low, but because it's running stinkin' rich.

In summary, I think you have a boost leak between the turbo outlet and the intake ports. Check all vacuum connections to/from the manifold, check all the turbo and IC piping and all joints, check the infamous "L" hose, etc. And since you replaced the head, check your intake manifold gasket area. IIRC the bolts only take 7 ft-lbs torque, if those are over-torqued or unevenly torqued you could have a manifold gasket leak.​
 

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Discussion Starter #8
1.8t Boost Pressure

Hi made up a boost leak detector yesterday and the only leak i could find (using soapy water as a leak indicator) was very slight from 2 of the injector seals .
Could this be enough to loose boost preassure (2psi) ????
Also i can both suck and blow through the DV vaccum pipe ,is this normal??.
Found when this pipe is plugged the vaccum goes up substantially ,and when i road tested the car although the boost had not increased the car was more responsive and revved up to about 5k freely .
Could this DV be part of my boost /vaccum leak??
Please help have posted this on the forum also .
Thanks Neil
 

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Discussion Starter #9
1.8t Aeb Boost Preassure/ Dv

Hi i am looking for a lack of boost pressure and performance on my 1.8t aeb motor ,when testing the DV i found that i can both suck and blow through the DV vaccum pipe ,is this normal??.(got nothing to compare with)
With the the DV vac pipe plugged the vaccum when measured goes up by about half again ,on road test this increased the throttle response,but boost pressure remained @ 5psi .
Any info on this much appreciated.:confused:
 

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The way Internet forums work, you don't start a new thread, you post updates to the original thread.

Merged.
 

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Pull your fuel rail and CAREFULLY clean the injector seals with your favorite alcohol-based solvent. You don't have to be very gentle with the kind of solvent, because the injectors ARE exposed to gasoline, after all.

Use Q-Tips to clean the inside of the injector housings. No-name cotton swabs are not recommended, as they have less cotton at the tip and they may cause damage if you push them too far in.











:D
 

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I would try replacing the DV first. You shouldn't be able to blow or suck through the DV's vacuum hose.
 

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Somebody double-check my logic here:

I believe you may have a major boost/vacuum leak. Under no boost (closed-loop operation), it turns into a vacuum leak. A vacuum leak introduces unmetered air into the system. This causes the O2 sensor to read "lean," so the fuel trims go positive to compensate (because of the closed-loop feedback).

The leak is post-turbo-outlet, so it turns into a boost leak under boost, so you don't get full boost, and it runs rich, but you're open-loop so there's no feedback and the trims don't compensate, so it stinks and has no power, not only because the boost is low, but because it's running stinkin' rich.

In summary, I think you have a boost leak between the turbo outlet and the intake ports. Check all vacuum connections to/from the manifold, check all the turbo and IC piping and all joints, check the infamous "L" hose, etc. And since you replaced the head, check your intake manifold gasket area. IIRC the bolts only take 7 ft-lbs torque, if those are over-torqued or unevenly torqued you could have a manifold gasket leak.​
There is a broad range range of engine operation when the turbo is producing boost, but the system is still in closed-loop: when the "part-throttle" mode is indicated on measuring block 005, field 4.

I think it is more likely that the leak is vacuum-only: in other words the leak is located "behind" a check valve, or is pre-turbo.

...actual fuel trim data would be nice... :poke: :lol:

Clogged injectors aren't very common -- i'd suspect a bad MAF sensor first.

also, the "eggy" smell may mean a failing o2 sensor, clogged cat, bad gas, or fouled plugs... it's hard to tell with the data we've got.
 

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...actual fuel trim data would be nice... :poke: :lol:
Ditto. I wasn't sure if "fuel adaptation keeps rising" meant bigger + numbers or deeper - numbers. Sounds like the DV is shot, but the trims would help narrow it down.
 

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Discussion Starter #16
Thanks for the info guys,much appreciated,will try and scan this weekend and get some fuel trim figures for you to check.
P.s got myself another DV to play with ,this one is from a 2001 golf 06A145710N,I CANNOT SUCK OR BLOW THROUGH THE VACCUM CONECTION ON THIS ONE ! so it will be interesting to check the results at the weekend.
Thanks again everyone for your input
 

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Thanks for the info guys,much appreciated,will try and scan this weekend and get some fuel trim figures for you to check.
P.s got myself another DV to play with ,this one is from a 2001 golf 06A145710N,I CANNOT SUCK OR BLOW THROUGH THE VACCUM CONECTION ON THIS ONE ! so it will be interesting to check the results at the weekend.
Thanks again everyone for your input
He said he can't suck or blow. Huh, huh, huhhh, huhh, huh.:D
 

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Discussion Starter #19
Right today i replaced the DV that has made a slight improvement .
Also removed the injector plastic guides ,cleaned and coated in high melting point grease to seal the threads,cleaned injector "O" ring seals.
Checked the fuel trim using snap on solus scanner data as follows.
(vag calls it learned value for mixture formation )
MVB 008 COOLANT TEMP 81C IDLE SPEED 840 (BEFORE DV REPLACED)
1 2 3 4
1.46ms 0.7% 0.0% ACTIVE


MVB008 AFTER ALLOWING TO IDLE FOR 15 MINS WITH NEW DV.
1 2 3 4
1.80ms 0.0% 0.0% active


MVB008 AFTER 5 MILE DRIVE.
1 2 3 4
1.80ms 1.5% -1.5% active

MVB21 LAMBDA
1 2 3 4
840rpm 0.95ms 85c closed

MVB009 LAMBDA
1 2 3 4
860rpm -1.5 to 4.6% 0.080 to 0.865 v 1.5%
Vaccum measured with gauge 18 in.Hg @ idle.

Have also just realised after checking,the head i have fitted is from a APU engine and has smaller ports than the original AEB head ,i realise this is not ideal ,but i could either change the manifolds to suit or open blend the inlet port to match the mainfold,not so bad the on the exhaust as the step is the other way i.e small into big.
Does anyone know if the cam profiles are the same between the AEB & APU motors ,could this be my prob??????.
P.s still only getting 5.5psi boost pressure max.
Any help much appreciated on this as im really running out of options now!!.:confused: :confused:
 

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Discussion Starter #20
Oh forgot to mention my MAF readings , the max reading taken @ redline isbetween 87& 95g/s vag.com says that for a std 1.8t you should get around 120g/s what do you all think of my figures??
 
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