Hi all,
I've just got hold of an old XM petrol turbo. Yellow check engine light is on all the time. It used to go out after warm-up and a bit of harsh driving, but now it's on all the time.
My Gunsons fault code reader tells me that there is a problem with the 'Turbo pressure valve' which I take to mean the wastegate.
The car lacks the power it once had, and I've noticed that there is a slight ticking blow from the exhaust manifold. Also looking from underneath I can see that there is a slight crack on the exhaust side of the turbocharger housing. It doesn't seem to be blowing there (no soot or gas leaks), but I don't like the look of it in any case.
Any turbo heads out there have any suggestions??
Turbocharger blues
Moderator: RichardW
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philhoward
Hi Alex, Have you checked to see if the wastegate actuating lever is free to move? If it has seized the wastegate will either stick in the closed position therefore causing an overpressure fault (not good for the engine) or if seized open will make the car feel sluggish due to poor boost pressures. What does the turbo boost gauge do when you accelerate? If the needle buries itself in the red, then you have a potential overboost problem, but if the needle seems reluctant to move at all then suspect a wastegate that's stuck open.
Good luck
Good luck
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philhoward
Alex,
I've had a look through my series 2 manual but can't find any injection system which controls the turbo. Certainly my 2.5TD has a purely mechanical turbo. The turbo wastegate is operated by a mechanical arm which in turn is actuated by a diaphragm linked to the downstream pressure. There's no electrical connections at all.
Read about my woes here:
http://club-xm.com/forum/viewtopic.php?t=17
http://www.andyspares.com/discussionfor ... erms=turbo
I don't know if yours is series 1 or 2 but if a mechanically operated wastegate then check the arm for free movement.
cheers
norrie
I've had a look through my series 2 manual but can't find any injection system which controls the turbo. Certainly my 2.5TD has a purely mechanical turbo. The turbo wastegate is operated by a mechanical arm which in turn is actuated by a diaphragm linked to the downstream pressure. There's no electrical connections at all.
Read about my woes here:
http://club-xm.com/forum/viewtopic.php?t=17
http://www.andyspares.com/discussionfor ... erms=turbo
I don't know if yours is series 1 or 2 but if a mechanically operated wastegate then check the arm for free movement.
cheers
norrie
hi alex
i used to have a series 1 2.0 turbo si this used to put up the yellow light
the problem was the pressure switch which is situated on the bulkhead just to the right of the engine
what happens is the ecu talks to this valve to denote what boost the turbo is runing if the valve is faulty
the ecu resorts to a base map(limp home mode)
it looses alot of power
2 choices here either replace the valve(expensive from cit at around £350)
or get it custom chipped so you can bypass this valve (but you have to remove the bulb as its on all the time)and then you just have a single map but you don't need the limp home mode
this costs around the same £300-350
but you get loads more power mine was 165bhp at the wheels
standard it's 144bhp at the flywheel(about 120bhp@wheels)
the cracks in the turbo are common they changed the housing on mk2 xm
but there like rocking horse s**t to get hold of
but if the cracks are serious internally it like having the wastegate open so you'll produce little boost but it will be better while it's cold than when it's hot(cracks get bigger)
---hth---
--neil--
p.s noz my 2.5 td has a similar boost control valve mounted on the bulkhead as the petrol one if you try for too much boost on the 2.5td it cuts the diesel off to prevent damage almost like a severe miss fire
i used to have a series 1 2.0 turbo si this used to put up the yellow light
the problem was the pressure switch which is situated on the bulkhead just to the right of the engine
what happens is the ecu talks to this valve to denote what boost the turbo is runing if the valve is faulty
the ecu resorts to a base map(limp home mode)
it looses alot of power
2 choices here either replace the valve(expensive from cit at around £350)
or get it custom chipped so you can bypass this valve (but you have to remove the bulb as its on all the time)and then you just have a single map but you don't need the limp home mode
this costs around the same £300-350
but you get loads more power mine was 165bhp at the wheels
standard it's 144bhp at the flywheel(about 120bhp@wheels)
the cracks in the turbo are common they changed the housing on mk2 xm
but there like rocking horse s**t to get hold of
but if the cracks are serious internally it like having the wastegate open so you'll produce little boost but it will be better while it's cold than when it's hot(cracks get bigger)
---hth---
--neil--
p.s noz my 2.5 td has a similar boost control valve mounted on the bulkhead as the petrol one if you try for too much boost on the 2.5td it cuts the diesel off to prevent damage almost like a severe miss fire