Technical MAF problem ? No power, where are horses? JTD 115

[momoto33127]

Hello,

First, sorry for my bad english, I'm french...

I have a problem with my Stilo 1.9 8V JTD 115 with 310 000km, I haven't power...

I have power problems since I have the car, the 0 to 100 is done in 16-17 seconds

I tried to loosen the necklaces, I change a hose of the turbo (the one coming out of the intercooler), I try injector cleaners, nothing helps, or very little
I tested the injectors with the return in plastic cups, there is a maximum eccart of 12% , so it's good ?
My idle is very stable (between 848 and 852rpm)
The stem of the wastegate moves freely over several millimeters
No particular smoke, Only when I put the foot on the floor while being in neutral, when the engine arrives at 5000rpm big black cloud ca repaint the ground, but it is one of the rare case where it smokes


A few days ago, I condemned the EGR valve with an aluminum plate but this one did not resiste with the heat, so I put a flange for the JTDM (with holes in it), and I put another MAF sensor I had at home (a Chinese thing) and I unplugged the battery for 1 hour.
Since instead of having the turbo that starts to "well" push to the 1800rpm it grows rather 2200tr / min

So I gave the original MAF (bosch) but not much change, I put my plate(I redid a brass plate this time, the brass holds the heat better) instead of the flange of JTDM, it has not returned either as before ... I unplugged the battery 1h, nothing ... So basically, I returned to the normal configuration (just an aluminum flange and the original MAF sensor) and yet I did not get the turbo at 1800tr

I even had mismatches with the original MAJ, I made the decision to unplug it, and the car responded without clashes

I bought a new bosch MAJ sensor, I mounted it earlier, unplugged battery 1h, I found a lot of power, but still above 2200tr, before that, I do not have a lot, the car is soft under the 2200

I have a hole between 2800 and 3100rpm~

The pressure of my turbo is ok...

No error in MES...

This is my logs in attachments

yellow = RPM
grey = % accelerator
green = admission pressure goal
light blue = admission pressure measured
Orange = MAF goal in mg/i
dark blue = MAF measured in mg/i


We see that the measured airflow is half the objective... It's normal ?

A friend with a fiat grande punto 70ch jtdm sticks me behind in terms of performance ..
Another with a Citroen C4 90cv HDI 200 000km exceeds me very widely while they are cars with a relatively close weight...

Thank you!

 

[Ralf S.]

The JTD has nearly a million different hoses on the intake side, so it's very possible you have an induction leak.

The first thing to do is to remove the under-tray (if you have one) and check the tightness of the clamps on all the hoses. The main ones are the ones on the turbo and the MAF into the airbox... but there are hoses to the intercooler and out of the back of the airbox too. Make sure they're all tight.

You already have a new MAF and a new MAP sensor (the one on the back of the inlet manifold).. so that's good... and the EGR is blanked off, which is also good.

But while you're here... remove the throttle body and clean out the inlet manifold. The EGR valve feeds soot from the exhaust into the intake manifold. The engine breather also blows oil into the intake manifold. They end up filling the manifold with a kind of tar... so even though the EGR is now blanked, the manifold might still need cleaning. When you fill the engine oil, only fill it about 80%. This reduces the amount of oil vapour that is vented into the manifold in future.

You also need to look at the turbo boost valve. This is an electric motor which is under the left headlamp (inside the bumper, next to the airbox). It assists the turbo to make boost... and gets some air under light pressure from the turbo boost solenoid at the front of the engine. The valve is connected to the solenoid by a blue pipe, if yours is original.

The valve gets covered in dirt and water, especially if the wheel arch liner is damaged.. so it can get corroded connectors or just fail. Or the blue pipe may have a split in it and might be losing pressure. Check that the pipe is good. I don't know how to test the valve .. I just replaced mine, even though it's not very cheap.

Some people move the valve to a location behind the headlamp, to better protect it.. but on mine, the valve didn't look like it was getting wet/dirty... so I left mine where it is.

The airbox has a little vent box underneath.. but I don't think this does much... I've run mine with and without the box and it doesn't make any difference.. so I refit the box and strapped it to the airbox.


Ralf S.

 

[momoto33127]

Thank you for your answer,
My intake manifold is clean, I cleaned it 1 month ago and today I just spent a cleaning product for 2 hours, the result is really not bad (in attachment)

Thanks to this cleaning, I gained a little nervousness after the 2200 rpm but it did not change anything before this diet


This weekend I will take a look at N75 valve(especially since I no longer have the engine protections under the car), I will also test driving without the exhaust line to see if it would not be my catalyst that would be clogged

 

[Ralf S.]

Good work on the manifold. Having a clean manifold isn't *essential* but if it's full of oil and soot, that can clog up the MAP sensor on the back of the manifold.

There's a small gallery where the MAP sensor connects to the inlet manifold, so it can draw in any oil and soot and eventually become contaminated.

Interesting theory re. the catalytic converter... especially since you wrote that the aluminium EGR valve blanking piece got too hot. It'll be interesting to see what bypassing the cat' does.


Ralf S.

 

[momoto33127]

Hello,

Today I inspected all the intake circuit and clean the air filter, tighten the hose clamps, check the turbo (the "games" (I don't know the translation)? are perfect)
I tested to ride without the line (I just left the precatalytic), I gained 4 seconds on the 0 to 100 km / h. No more holes in the acceleration, but it still remains slow below 2000 rpm

I put the line back, and the holes did not come back!

The values on MES during the test without the exhaust line are better, the differences between measured and required are lower!