About 2 years ago my Mazda 6 started idling very roughly when started from cold and also had a fairly loud knock. Once it's warm it ran OK but lacked the usual power. My mechanic referred me to a diesel specialist who stripped out the injectors and tested them. He said the nozzles had seized because of bad fuel. I live in a border county and re-fill at the same station. He cleaned the nozzles and the car ran OK for about 6 months then started giving problems again. I took it back to the same diesel specialist who replaced the nozzles on the injectors. After that it ran OK for over a year but has started giving the same problem again.

I took it to a different mechanic and didn't tell him about the history. He investigated and also said the problem was with the injectors. He rang another diesel specialist who told him the Mazda 6 probably has denso injectors which can't be repair/reconditioned and will have to be replaced.

Has anyone had a similar experience with a Mazda 6 or know anything about denso injectors?