159 2.4 JTDm engine issue

[Alfa-mad]

Hi guys, I joined in 2017 when I got a 159 2.2 selespeed but ended up selling that before anything major happened. Instead, I got myself a 159 2.4 JTDm with QTronic which is just so much more enjoyable to drive and the exhaust note is actually not bad at all, especially when on boost.

Anyway, I've been getting an issue especially when the car hasn't reached running temp, that when cruising around 50kph which is in the vicinity of 1500rpm, the engine gets jerky and hesitant. Full throttle there is no issue and once warmed up it goes away.

So I thought it was a good time to take off the EGR and see whats happening and turns out the intake manifold is full of gunk, no surprise there. The EGR itself was quite clean inside, just a very thing carbon coating but no chunky buildup and the valve operation was smooth.

Looking at the throttle body though, it was definitely suffering from a build up of carbon and oil deposits. So much so that even when you moved the butterfly open about a quarter, there was enough gunk causing a restriction that I thought this had to be cause. Once I cleaned up the throttle body I also could see inside the intake manifold and there is easily about 1cm thick of carbon coating the walls. Some had come loose when I removed the throttle body so I loosened as much of it as I could and vacuumed it up. Taking the intake manifold off is a job for another day.

Once I put it all back together and went for a test drive, sure enough the jerkiness and hesitation had disappeared, it was smooth driving so that was solved.

However, the engine clearly had another issue where it accelerates very slowly, transmission won't kick down and I can barely get boost pressure. At first I thought perhaps I didn't tighten something or forgot to plug something in but a double check revealed that wasn't the case.

The issue was one little flexible pipe at the back of the engine which must of been bumped off when I was taking off the EGR. Once I put it back on, car is back to normal making boost etc.

But this leads me to some questions that I'm sure an Alfa guru lurking here might know the answer to. I've posted pictures to show what I'm talking about.

In this first attached pic, the arrow is pointing to the tube which was detached, but what is the black plastic box that it attaches to? I've also traced its path in red so we can follow it on the other pics.

[Alfa-mad]

And in the next attached pic, you can trace the red pipe which ends at I think the camshaft position sensor housing? Any ideas there? And if so, why would unplugging that tube cause the limp mode?

[Alfa-mad]

And finally in this last pic, I've also traced the other pipe using an orange line, this goes from the same black plastic box below the EGR, all the way to some kind of valve above the radiator, does anyone know what that does?

[Alfa-mad]

Here is a pic of my EGR valve, the inside was nothing of note but the gasket looks like aftermarket restrictor plates I've seen but this one looks like factory gasket. But this engine is the slightly improved version in a 2009 model so its possible the took a leaf out of the aftermarket and changed it.

[Alfa-mad]

And here is a pic of the entrance to the intake manifold. A bit hard to see but there is so much carbon buildup, I'm going to do the whole manifold removal and clean in about another 20 thousand kms which is when I'll also change the cam belt and water pump etc.

[bazzbazz]

And finally in this last pic, I've also traced the other pipe using an orange line, this goes from the same black plastic box below the EGR, all the way to some kind of valve above the radiator, does anyone know what that does?

That is your Boost Control Solenoid.

[bazzbazz]

In this first attached pic, the arrow is pointing to the tube which was detached, but what is the black plastic box that it attaches to? I've also traced its path in red so we can follow it on the other pics.

I think you will find that's the Vacuum Reservoir

[bazzbazz]

Here is a pic of my EGR valve, the inside was nothing of note but the gasket looks like aftermarket restrictor plates I've seen but this one looks like factory gasket. But this engine is the slightly improved version in a 2009 model so its possible the took a leaf out of the aftermarket and changed it.

The aftermarket gasket is a plate that blocks off the whole EGR and has 4 holes in it (in addition to the bolts holes) to allow a minimum of exhaust gasses to re-enter the manifold.

Like this -

[Alfa-mad]

Cheers for the info about the vacuume reservoir and boost control solenoid. It never crossed my mind to be that since the way its plumbed seems to be a bit make shift, I would of expected a more streamlined design but then again, most cars I've had haven't been transverse layout.

Regarding the restrictor plate, i assumed that was factory but you're saying that is actually an aftermarket one? I didn't think it was as the quality is OEM, very good.

[bazzbazz]

Aftermarket = Updated part.

[Domenic]

Bazz,

It's not an aftermarket part. It's an original Alfa Romeo part from the factory.

[bazzbazz]

I DID correct myself stating UPDATED part, sorry if I wasn't clear.   

[Winno]

Any EGR plate which doesn't block 100% is delaying the inevitable. But you'll then need a TAFMET plug-in module to trick the ECU or remap so you don't get errors.