Audi 90 with aan engine problem, cutting fuel

[KimiTG]

hello .. I'm working on one project, audi 90 coupe with aan engine from the Audi S4. the engine is loaded and everything is done. I have one big problem that solves for a month. my audio works nicely at idle throttle. in first gear all goes well, but when in the second, third, fourth and fifth gears under load ECU cut fuel ... nice start but after a time at about 3000-4000 rpm simply disconnect injectors. When that happens I put off the throttle again back and add gas. My audi then raises rpm , and after 3-4 seconds, back down. It is constantly repeated, when it's hot and when it is cold ... diagnosis does not occur any error, at that point the pressure turbo is 0.85 bar and 3.7 bar fuel pressure ... help please

[martinws]

Sounds like a boost cut. No fault codes at all?

[ManiacuV6]

What spark plugs do you use ?

[Tonks4x4]

Agree with a boost leak. Or N75 has been replaced and is using a manual control set too high.
Or ECU map sensor is too small?

[rynaqui]

Does it judder violently when it cuts? Does it cut every single time? Have you checked the MAF? This is on stock turbo? Could be as mentioned above a bad map sensor..

[KimiTG]

no fault codes at all.
im using original spark plugs from the auto data
the engine is stock,map sensor is original too,n75 is stock as well.
it dosent studder it just disconects straight away same as you turned it off by key.
it happens every single time in 2nd,3rd,4th and 5th,in 1st never,MAF is checked same as all other sensors,no fault codes,all sensors are changed with new ones and it still happens.It is a stock turbo,stock engine,no customs. We even tried a new ECU and the thing still cuts out.
Could it be because the engine is out of a car with a automatic gearbox,does it need any addaptive ECUs

[KimiTG]

no fault codes at all
using original spark plugs from auto data
n75 is stock like all other sensors,all sensors a changed with new ones,ECU map sensor is original,and we used a another ECU from a good working audi
it dosent judder,it just cuts out and it does cut out in all gears except in first gear,turbo is stock and maf is checked.
could it be because the engine was from a car with a automatic gearbox,does it need any additional ecus or moduls.

[KimiTG]

read forum

[rynaqui]

What about the fuel pump and injectors? Are they in good condition? Also coil pack and wiring..it is less noticeable in 1st gear I imagine as with most problems related to a car behaving like this because of less load.

What about the downpipe?

[Pirvu Eugen]

Boost leak or MAF, MAF plug or wiring.

[KimiTG]

no, not MAF. MAF sensor is a new purchase, contact wires were cleaned and not break ... I've checked everything. I really have no idea anymore

[KimiTG]

fuel pump is also new, injectors are tested and in good condition. coils and wires were inspected, POS (Power Output Stage) have been changed. what is it Downpipe? Perhaps it will help if I tell you that a car going without interruption when I unplug the turbine, when I'm driving as atmosferic engine. Then everything is fine

[rynaqui]

My knowledge is very limited, someone with more experience would be able to tell more or less what is the cause of your problem. By turbine you mean the turbo itself?

Could be related to the downpipe as mentioned or the exhaust manifold, turbine housing etc..someone else may be able to help further as I'm not the right person for this

[KimiTG]

I just made it that you are the right person for these things. really have no idea anymore

[driftin jo]

Surely if the ecu was cutting due to a boost leak there would be a code .
How do you have the ecu wired ? The ecu needs constant power to keep the codes.
If you are removing all power from it when you turn the ignition off you will be clearing the codes, just a thought, as this is a transplant.