S40 T4 power/boost/hesitation issues. How did you solve?

[VectorBr]

Since we know our T4's engines are fussy and there are so many threads from different users about power loss / hesitating / boost issues on S40 T4's, I think it would be great if we share our experiences about this in one thread.

The idea is to tell what your car is (or was), what happened (the symptoms) and what you did to solve that. Feel free to add pics or talk about other's cars. Let's build a knowledge base..

My T4 is a 1998 model, and I'm having the hesitation / hiccups issues under WOT. First I thought that was a ignition problem, but it was not solved after a new spark plugs kit and coils change. After that I checked for boost leaks and found only a small leakage on the hard hose that goes from inlet to brake (vacuum) system. I don't know if it can affect the car's performance under load, and it's not solved yet.

Now I'm pointing at the fuel pump or the FPR direction, since I'm getting problems in hot starts and the car got more than 80k miles with standard pump / FPR.

Well, it's in a performance garage right now so they can test the rail and pump pressure, filter and FPR appropriately.

BTW, STFT is always negative (between -20% and -5%) and LTFT is positive at +3.8%
Besides that, there are no codes stored, at least accordingly to my OBDII torque app.

[VectorBr]

Just an update. After the tests:

We discovered a loose clamp inside fuel pump, and besides that, my fuel filter was mounted inverted, so the filter element inside was shaking, therefore blocking the fuel. That`s why sometimes acceleration was good, other times was not (losing power and hiccups when WOT).

Fuel pump itself is in very good condition, 150 lph at 4 bar.

Spark plugs and coils are brand new.

There are no more leaks (except the one I mentioned, the hard hose that goes from inlet to brake (vacuum) system). It`s now fixed.

And after tightening the clamp inside the pump and replacing the fuel filter, now my T4 pulls very very hard again as it should be. No more hesitations.

[mitchyboy01]

Originally Posted by VectorBr

Just an update. After the tests:

We discovered a loose clamp inside fuel pump, and besides that, my fuel filter was mounted inverted, so the filter element inside was shaking, therefore blocking the fuel. That`s why sometimes acceleration was good, other times was not (losing power and hiccups when WOT).

Fuel pump itself is in very good condition, 150 lph at 4 bar.

Spark plugs and coils are brand new.

There are no more leaks (except the one I mentioned, the hard hose that goes from inlet to brake (vacuum) system). It`s now fixed.

And after tightening the clamp inside the pump and replacing the fuel filter, now my T4 pulls very very hard again as it should be. No more hesitations.

Very interesting. Do you mean the in-tank filter (on the pump) or the external filter?

[VectorBr]

Originally Posted by mitchyboy01

Very interesting. Do you mean the in-tank filter (on the pump) or the external filter?

External filter... was mounted in the wrong direction! Incredible how them could do something like that

[960kg]

It is very very easy to do that!.......and the reason being my `98 T4 external filter was replaced by my self and it WAS the wrong way around but did not suffer any running problems and it should not on any X40.

But the arrow on the filter should face the front and the reason some are facing the wrong way is because when underneath upside down the fuel lines from the tank go around in a circular fashion they do not go direct to the front as there is another FPR at the rear and to enable it to be fitted correctly the fuel lines are coiled around ....so one has to follow these coils and sometimes the filter IS pointing the wrong way but is still in the direction of fuel flow.......

Hope you followed that!........you can still put in the wrong way and it will cause no ill effects except that it may not filter as good as it would the correct way!

It will be the incorrect spark plugs that caused your hiccups at WOT.