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Discussion Starter · #1 ·

I'm having some problems with my 155 Q4.
The turbo kicks in around 2800 rpm as it should be.
Problems start around 4500 rpm when the engine starts to work heavy and the sound from the engine gets harder. This repeats at around 5500 rpm. It seems as the engine starts to work against it self....loosing alittle bit of power as well.

:confused: What can this be???
There is a system to prevent "misfire"(don't know the english word for it). What does it do first??? Lower the ignition, raise the fuelpressure or lower the boost???

The car might be chipped and not correctly mapped afterwards....we are checking that possibility too.

all help is welcome, this is starting to get on my nerves........ :mad:


56 Posts
Hi ,
Andreas is explain me problem.
I understand, your turbo is work very good condition ,especialy start 2800 rpm .
You must check some value first.
You drive a turbo car and spark -air and fuel value more important another cars.
When you install original eprom ,
you must check spark - fuel and air value again .
Check on the turbo label for the connected correct turbo.

First ,
You can change spark timing a bit little use with variable timimg sensor.It is place on the left side engine ,
if you look the engine front side placed right side engine and connected exthaus cam.You can make re spark timing correct value with use timing light gun.
This is make advance or retard spark timing.

You must connect a pressure gauge between fuel pipe and enjectors .You must read 2.5 bar fuel pressure ,if not correct ,you can adjusted it on the fuel pressure device.

You must connect a boost meter on the intake manifold,use with a T pipe .
You must read maximum turbo pressure 0.8 or max 0.9 bar on the boost .

So ,
where is come noise in to engine ? could you check it ? when you press accelerator on idle (no gear,no on the road or when no load) can you hear same heavy sound in the engine compartment ?
I mean ,,Q4 is use electronic boost control device ,its name is pieerburg ,if you dont use your car on the road ,when you press accelerate ,,turbo isnt activity ..


Discussion Starter · #3 ·
sometimes one oft the two small vacuum tubes at the small cylindric vacuum reservoir, fixed at the black front sheet metal, just above the turbo gets off by itself (easy to find). Check this!
Maybe it's easy like that?!

CU, Spike

Discussion Starter · #4 ·

Changed the airfilter and the plugs on friday. Took it for a spin and it felt alot better. Engine wanted to pull alittle more and revved just alittle bit more.
Also it didn't seem to work against it self as much as before.

On saturday, we checked the fuelinjectors...nothing wrong.
We also connected a turbopressure gauge to the car and took it out on the freeway.
It loaded around 0,6 bars and the pressure was constant.
The hard noise during acceleration, is probably due to the poor exhaust or a poor fastening of it.

Q: what is the correct boost pressure for the -93???

I'm gonna check the vacuumtubes today after work.

We came to the conclusion that I do need an Ignition adjustment and probably a new exhaust as well(the old one has been tampered with and repaired with some welding)

Updates will come as soon as I know myself...

Tom C, Sweden

56 Posts
I know nominal pressure is 0.7 between 0.8 bar and maximum is 0.93 bar ..
A idea ?
Could you record your cars voice ? and than send me via email?
I can listen it my alfaromeo service .


Discussion Starter · #6 ·
I will try and record my car.
But that will have to wait for a little while.
Right now I'm moving to a new home and I will be busy for two weeks forward.


Discussion Starter · #7 ·

Got the original chip in today and took it for a spin.
It feels like the car can pull a little further now and the problems at 5000rpm is gone. Turbo spools up around 2800-3000rpm.

I can notice some "twitchin" during acceleration(like an ignition problem maybe). Maybe just some clogg, beacuse the engine goes better and better as I USE the car.
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