Help needed

[Coffee76]

Hi all,

Help needed, as said in my introductory post my 147 diesel is off the road at the moment I suspect a manifold air pressure issue, any advice on where it is located or pics would be appreciated.

Cheers

Shane

[Evan Bottcher]

Hi Shane,

I've cleaned the MAP sensor (manifold absolute pressure) on our 2.4 JTDm a couple of times.  It definitely seems to affect the low down responsiveness if it's clogged with soot.  No idea if it'll fix your problem however, there seems to be a range of minor problems that can affect these diesels with similar symptoms.

The attached image came from a google search and is from the alfaowner.com forum, a british website which has lots of info on the modern Alfas.  This is of a 1.9 JTD like yours it appears to be in a very similar spot to on our 2.4 - with the plastic top cover off it is at the top rear left of the engine on the inlet manifold.  It has an electrical connector which you unclip using a flat screwdriver and the connecter will then pull off.  There should be one torx screw holding the sensor to the inlet manifold, then you gently twist the sensor out from the manifold.  It has a plastic snout/cage which I believe holds both a temperature and pressure sensor.  Ours has been heavily coated in soot in the past, I've used electrical contact cleaner to wash it clean, then reinsert it and bolt it back up.

Seemed to make a good positive difference last time I did it, unfortunately due to the turbo and EGR valve the inlets of these get sticky and sooty which leads to a build up all over everything inside the inlet.

P.S.  Remember I'm not an expert, no warranty on my advice.  If you're uncertain, call into an alfa specialist (one of our club sponsors) and get some advice.  Cleaning the MAP sensor will only take them five minutes.

cheers,
Evan.

[Coffee76]

Thanks mate appreciated and no warranty implied  will let you know how I go on the weekend !

[Craig_m67]

I have a 1.9JTD
Why do you suspect manifold air pressure issue... Sounds like an error code?

What are the symptoms?

Easy things to check for are split boost hoses. There are two, first goes from the turbo under/along the back of the radiator to the charge cooler. the second goes up inside/along the LH wing and into the plenum. Both of mine spilt independently, due to age and have been replaced.

Check the MAF is operating, there is a noticeable difference in driving when it's disconnected. Unplugging it will flag an error, however it goes away after five starts with it plugged back in.

Check that the MAP isn't gunked up as Evan suggests, it's located on the back of the plenum held in by a single screw/bolt

Check the operation of the EGR valve and that its not gunked up as well. Unplug it and you will get an error like the MAF which will clear later, again it should make a noticeable difference to take off. You Can also take it off for cleaning, four bolts from memory into the plenum and two for the metal hose - don't loose the metal gaskets (ask me how I know)

The later engines (yours) have swirl valves in the plenum which cake up with soot and crap too. Eventually these need cleaning or replacing as the soot wears/grinds them up. 

Removing and cleaning the EGR valve, MAP and plenum is a good step if you are brave/can be arsed. You can't really clean the MAF sensor (top of the air box) best just to buy an OEM!! replacement. 

Only other thing to check is that the vacuum actuator for the variable vane (stuff) in the turbo is operating, you can see the little rod move a half centermeter or so when the engine is started (by somebody else). The vacuum actuator is just behind the radiator at the top with the rod going down into the turbo.

My money is on a split hose, air leak etc.
I've noticed no difference between the high performance fuels, I do add a bit of oil to the fuel (like a two stroke) every ten or so tanks as it seems to quieter down the clatter, injectors or pump maybe, dunno, but it does work


I've never had a MAF, MAP or EGR issue with my car (180,000ks).. Just two split boost hoses, the lower one was a bugger to diagnose (I'm lazy, meant bending down) and a dodgy aux belt tensioner which made it sound like a bag of spanners

Having driven Alfas for 27 yrs, I do keep MAF, MAP, EGR, aux & cam belts and a waterprump in my preventative maintenance kit  - I need to reorder the tensioner and idlers as these are all consumables that are easily replaced (with a little courage, help etc). I recommend EB Spares UK for bits for this model, they always have it and quickly.

[Coffee76]

Thanks Craig, the MAP sensor was clogged like you wouldn't believe wil post pics later, disconnected it to see it run without and made quite a difference, cleaned put back in and tried again, a little better but not much. Yes did get an error code, couldn't be arsed trying all the other stuff haven't got time, so can anyone recommend an alfa mechanic near Wetherill park ?

Also thanks for the help guys really appreciated, Evan the pics pointed me in the right direction !

[Coffee76]

Ok so MAP sensor is clean, now get a motor system failure warning and a marginal improvement, looks like a trip to a friendly mechanic !

[Coffee76]

So $286.00 dollars lighter and one clean EGR Valve, unsure of why it was so expensive, given all they did was clean it and apparently put a panel over it ?? not sure what he did here.

[Craig_m67]

Did it solve the problem ?

[Coffee76]

Did it solve the problem ?

Yes it did ! In fact I didn't realise how much pick up the little beast has ! So it has obviously been a issue from the start, I just presumed it was a diesel and had no guts ! I am now happy with my Italian mistress ! She is expensive ..... But pretty !