I have a 1999 Ford Puma 1.7 with a juddering problem and have had two diagnostic checks, but no codes show up. When I take my foot off the accelerator, the car judders. So far I've replaced the catalytic converter (was told this could be the problem) and have changed the fuel filters, air filter, lambda sensor, plugs, idle control valve, cleaned the MAF sensor and checked all hoses, but it still judders and nothing is showing on the diagnostic machines. I am at a loss.