Puff, Puff

[AtlMB]

I just purchased a 1992 300d 2.5L of unknown history. I replaced a leaking injector line (the one most forward). The car starts beautifully, then after about 20 seconds, starts running rough. Puffs out of the exhaust. At operating temp, it is strong, with almost no smoke. The idle seems to grow progressively worse, with small puffs.

Is the injector on that cylnder just clogged? I gave her a small Italian Tune Up today to no avail.

Any help would be appreciated.

Thanks!

[t walgamuth]

I would suspect a bad valve or a tight one. I suggest a compression test. Before doing that it would not hurt to crack the injector lines one at a time to find the weak cylinder and then switch it with another and see if the miss follows the injector. If it does you know it is the injector. If not you know it is mechanical and probably a valve issue.