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Variable valve timing expert needed


richard bradbury

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My Citroen C4 Coupe has a 2.0 litre 16v with variable cams and has a claimed 180bhp. The same engine is used in some Peugeot GTi models. It has been working fine and one of its nicer aspects has been a sweet running nature with good sound insulation. I know it to have been fairly quick as it could hang onto my son's Honda Civic Type R. For convenience I had the car into a main Peugeot dealer in Morden to replace a slightly weepy water pump and change the cam belt at the same time. An oil change and filters were also done. Job done.

On driving I immediately noticed a big increase in induction noise and a loss of power. A wrong air filter was found and replaced. Drove car again-slightly quieter but still gutless. At 6000rpm engine cut power and went onto idle mode. Back to garage. Diagnosis- faulty throttle butterfly motor (drive by wire) £269 ouch! Picked up car to take on a weeks holiday- engine still noisy and down on power! They say they have checked the timing 3 times and all lines up. On holiday we did 3 timed accelerations from 40mph to 80 mph using 2nd and 3rd gears and it took as long as accelerating to 80 from a standstill. This indicates the car is about 20-25% down on power. When you drive with a light throttle it sounds and feels normal but when you open it up, there is a raucous noise and bugger all power.

I suspect the cam timing is the problem but as I do not know enough about the workings of variable cam motors, I do not know if it is possible for the timing to be out and yet the engine to seem normal at low revs and throttle openings but lacking in power and be noisy at higher revs. Is it possible for the second cam not to be opening? I am concerned that they will have the car back and say they cant find anything wrong. Is this the sort of problem that a good rolling road should be able to pinpoint the trouble, and if so, where I can find one in the South London area now that Southern Carbs no longer have one.

Help as I am getting desparate and more pennyless by the minute.

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I would return to garage (is it under warranty?) and say they have changed the characteristics of the car and must return it to how it was. I'd also ask them for a print out from the on-board computer to highlight there are no fault codes. Then I'd take a mechanic out with the same spec car in front and show how it won't keep up.

 

I hate to ask but is there any chance they got something wrong before and bent a valve or something? Or they have certainly disturbed something and maybe this has meant the VVT is no longer operating? I presume the Pug engine is not the same as a V-TEC in that it doesn't have a second cam lobe and instead has variable valve timing? It could be the mechanisms have been damaged or one of the many sensors has been disrupted. If the throttle body was changed and it made no difference I'd ask for the old one back and your money for it too.

 

I would think that a vehicle diagnostic is required - be warned they could cover this up so you might want to take to someone else. I would certainly be speaking to the manager/someone senior than trusting the front of desk service people. Amazing how much you can get done when you speak to the right person!

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The car is out of warranty. When the engine cut onto idle power a warning came up on the dash screen " engine management system fault". Having switched the engine off and re started it it worked ok so I was able to take it back to the garage. A fault code came up which indicated the throttle motor. Since fitting I have not experienced any more cutting out, but it has made no difference to the noise and lack of power. The only saving grace is that I have not yet settled the bill! I just want it returned to how it was.
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I have heard of this kind of power response when the internals of the cat have collapsed and are blocking gas flow - is there any jingling sound coming from the cat when you start the engine or rev it?

 

Phil

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