I have a Renault Scenic 1.6; I find it, for the engine size, to be powerful and economic (average 40 mpg and even cruising at 90mph never less than 35mpg). The car was run in very carefully for the first 3000 miles. It was bought new in March 2002, current mileage 16,500. Only one fault in that time, at 12,500 miles, a bad misfire below 2000 RPM, this was traced to a faulty coil on one of the plug leads. I booked in the car with the dealer from whom I purchased it, and the car was returned within four hours, running sweetly again. I suffer from lower back problems (mild not severe), and in the test-drive distance they allow you, it felt fine, it was not until I had done a journey over 20 miles that the inadequacies of the seat became apparent. I went through agonies! I returned to my dealer who was unable to sell me anything to help. It was only thanks to the staff of Halfords that I can now ride in reasonable comfort, as I was able to try various support devices and return them if unsuitable. I tried Renault UK; to say they were unhelpful is an understatement, they were worse than useless, even obstructive in one case, saying that if I replaced the seat I would invalidate the warranty! What a contrast to the dealer, who has been superb, extremely nice and as helpful as can be. Would I buy another? Difficult to say, depends what's on the market in 2005 when I replace it, but if I can find ANYTHING else that fits my needs as well as this - most certainly, simply because of the attitude of Renault UK.
My wife also drives a RX4, it's a great car, not very reliable, but fun.
The car shudders because of its four-wheel drive system. I noticed the symptom when making U turns when turning hard in second gear. The reason is, when there is a speed difference between the front and the rear wheels, the viscous clutch "locks" and does not allow enough speed difference between the axles.
Last Year my wife purchased a Renault Scenic RX4 petrol, shortly after this we noticed a problem with the steering twitching as we cornered right, a friend who had previously worked for Renault advised us it was a known fault of the steering rack.
Renault insisted on replacing the Power steering pump and rack (not a problem, I was on warranty), this cured this problem and the steering has been fine ever since.