I am having an issue with my 300D that is causing terrible incomplete combustion. It has terrible grayish white smoke at idle, and the exhaust smells horribly like unburned diesel. It gradually began doing this. The engine also nails terribly especially when in gear at a stop. I replaced the chain recently, and I think this all started about 2 months after replacing it. The engine runs much smoother on vegetable oil for some reason. I am thinking that maybe an injector or two is clogged. There is a noise at the rear injector that sounds like someone trying to suck the last bit of soda out of a straw, is that a sign of a clogged injector? It also began getting hard to start, and also began having no power, to the point were I was afraid of somebody rear ending me. So I took off the ALDA, and this solved the power issue, but it now smokes even worse, and has terrible mileage. What could the issue be?

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head