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 FAQ #227
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C4 2.0 HDi Turbo lacking power - what to check?
Hi all - just a recount of some of the problems I've had with my 2.0 HDI Coupe, and how they were fixed...

1. Rubber vacuum solenoid and actuator connector pipes.

There are quite a few of these in the vacuum system - mine perished and caused the turbo to suddenly stop working (because one on the actuator vacuum solenoid had fallen off). Have replaced them all now and turbo is back!

This is an easy thing to do, costs next to nothing and should be done I would say with engines over 5 yrs old.

2. Turbo actuator vacuum solenoid failed.

This still switched the vacuum off to the turbo actuator, however the air resistance had gone meaning the vacuum was rapidly being applied either full or none, without the 'smoothing' this valve should normally do. At light acceleration the car rapidly bunny hopped along. I've changed this today for a s/h one and all is good again.

The new one had good air resistance when blowing through it so I guess it is now smoothing things out as needed. As a word of warning - always fit the pipes the right way round, on the solenoids. The one to the vac pump goes to the inlet pipe labelled 'vac'; on mine this is also the pipe nearer the end of the solenoid. I got it wrong replacing the rubber pipes to the air mixer with the result that it shut off the air flow altogether and wouldn't open again until I switched the engine off - the car idled but the old right foot just made it smoke without the engine revving (i.e. more fuel and no air). On the turbo solenoid, getting them the wrong way round means the turbo won't come on at all.

3. High pressure pipe at bottom of intercooler

Badly fitted so had air leak - classic smoking and whistling. Easy enough to refit and solve this one.

4. Inlet to turbo come loose.

This is secured with a single bolt, which was missing so the pipe had popped out of the turbo inlet. Result - shrill whistling and some power loss. Easy enough to fix though once wipers and scuttle plate removed (this is not so hard as it sounds and once done allows access to turbo solenoid (as above) and EGR to remove and clean it).
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FAQ Posted by marksuts
Info Created: 04 August 2012
Last Updated: 04 August 2012