'80 300TD
Well I have just spent about half a day reading posts and only one comes close, but alas not quite.
I have been driving this car for about 4 years and the strongest thing has been the engine. No noise, nailing, knocking........until NOW
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I commute about 145 miles to work about 10-12 times a month. You read it right, almost 300 miles round trip in 24hrs. My engine has run smooth the whole time. As of late though I have been getting what I would describe as "nailing" at cruise speeds only. Yup, thats right at cruise speeds. Starts fine, I live in Florida so cold temp is really not a problem. No major smoke on start-up and seems to idle without any nailing. But, after accelerating with the cruise control on at hwy speed (70-75 mph) I get random nailing. Sometimes once in a while and then for about 5 seconds and then gone again for some of the trip and then back a little louder and there is no real rhyme or reason. When I exit the hwy and stop at the light at the end of the ramp, it idles pretty rough (car shakes more than out of sync idle though).
Around town I do not get any of these symptoms. I two can diesel purged her and followed with a Lubro Molly fuel additive chaser. Nothing changed. I changed both fuel filters after the purge and used different gas stations just to rule out the fuel contamination thing.
I have dumped more money than I had planned (yeah, I know, welcome to the club) to keep this running. I have done the work myself and all has gone well and then this rears its ugly head!
I am hoping this is an injector thing and not a knocking problem. If it is a knocking thing there will be a lot of new parts for sale on ebay really soon. The exterior of the car has a lot to be desired and until now I had a real strong running car. Well, I take that back the car seems to run just fine. No real lack of power, 23-24mpg hwy, little or no smoke, but eats a little too much oil for my taste.
Anyway, she'll be making the trip on Thursday again so any input would be helpful.