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156 jtd 2.4 turbo problem

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jtd turbo
3K views 27 replies 17 participants last post by  rmfrance 
#1 ·
Hello all Alfa owners,I just registered in the hope of advice for my 156jtd 2.4.Best car iv'e owned and enjoy driving it.Great on diesel.I had it serviced recently and the mechanic remarked that the turbo was slow coming in,but when in, took off.He admitted not knowing much about turbos.He thought it might be a valve?
It used to kick in about 1600 revs ,but it is now just over 2000 revs before it happens.Any help greatly appreciated.
Regards
 
#15 ·
Thanks all for welcome.To Bezste and jasons the car is Jan 2002,140bhp.The MAF hasnt been changed since ive had it,about 2 years.I read somewhere on this site that the MAF can be unplugged to prove a point.
I'm an Electronics man but reasonable mechanically.Seen the day of feeler guages in the tappets,change brake shoes/pads,oil but thats it.
The mechanics I know, admit of knowing little about Turbo.And I read Arnold Clark Aberdeen,has given up Alfa agency.Hence turning to you experts who are pointing to same thing,MAF.
Is it easy to get at and buy and fit if it's the culprit.?
Iv'e to check hoses yet as advised by Lotgrace Tradin.
Will close this now before computer decides to shut down again

Thanks
 
#16 ·
It could be vacuum related. The wastegate (open the bonnet and look straight down between the engine and the radiator) is vacuum operated and the vacuum pipes are pretty small. Might be worth tracing those back up and over the engine (under the cover) to check they are still intact.
 
#17 ·
It does sound like the wastegate actuator to me... open the bonnet & look at the front middle of the engine - there's the turbo. The actuator is the thing just in front of the turbo, which controls a lever on the turbo itself dumping unwanted boost into the exhaust. If it's badly adjusted (or not working) it'll drain power. Try moving it by hand - you should be able to (cold engine (not running) advisable as it's hot & dangerous otherwise).

Any warning lights on? A split boost hose will throw the engine warning light on, and spit oil out from the leak too, so very noticeable.

Welcome... and keep us posted.
 
#18 ·
I would definitely change the MAF. I think it should be compulsory to get a new MAF when you buy a secondhand 156 - it gives you a much "blanker" sheet to start with when you're troubleshooting all the other problems!

Don't bother disconnecting the MAF to see if it makes any difference - that doesn't work on the diesels!

I drove around for the first 6 months thinking "well this diesel is okay but nothing like as quick as my old 146 Twin Spark". Then I began to read the forums and decided to put a new MAF in - WOW:) After picking it up from the dealers I couldn't beleive the difference.

Half way down the road I actually pulled over, got out and checked they'd given me the right car back! Honest :eek:
 
#21 ·
Don't bother disconnecting the MAF to see if it makes any difference - that doesn't work on the diesels!
You're wrong there, depending on the problem with the MAF it can make it a lot better. If the MAF has properly failed, then disconnecting it will be a big improvement. If its just slightly misreading at higher revs, then as you say you won't notice any difference.

The thing to remember is that if the actuator is faulty its not replacable on its own......its a new turbo/actuator assembly that will be required !!!!!!!!

Lee
I think member 'darrude' on here managed to fix his own sticking actuator. Plenty of grease and a hammer did it! :eek: :lol:

If you're thinking about replacing stuff like that, a DIY fix is worth a try and will cost you nothing :)
 
#19 ·
simple (not conclusive) vnt test.
watch the actuator as someone else starts the car, you will see it pull within a second or two, also when they turn off you will see it release.

If it is stuck, a, it will not move/very little, b, you will lack power up to 2500rpm which is when the turbo will get spinning without the aid of the VNT.

AMF sounds goods also, but start with the cheapest as paddy and others have said, and check the actuator movement.
 
#27 ·
Hello again, I finally got back to this site to thank all inputs.
After getting service and MOT this month found a Turbo man/Garage only 4 miles from me hidden in the countryside.
Bingo! Plugged his test box in and suspected MAF.(Bezste & jasons thoughts)
Went back 2 days later to get it fitted.
Changing it was reasonably easy but he moved/knocked the elbow top of radiator and caused small leak.Have to go back and get fitted which is a push in with o-ring.
However leaving garage to go home!!!
J---s,,I thought when I bought the car it responded, but this is something else.It's instantaneous in any gear(and any revs it seems) when pressing your foot.Whoosh.Foot off.
Thanks all and happy new year.
Peter
 
#28 ·
Could this be a clue as to the weird behavior of my newly-acquired 156 2.4 jtd M-Jet? Just back from the Alps (love that ski-flap...) and noted during long mountain climbs a sudden surge in power as I hit 3000rpm, accompanied by a brief but embarrassing cloud of smoke.
The turbo is new, having been replaced for the previous owner by the official Alfa agents where I purchased the car - they told me that the problem turned out to be 'a valve', but they did the turbo anyway...
I'd appreciate any insight here, being new to all this !

Cheers
 
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