During the late 80s the ECU was intended to bring stability to currencies within Europe, with the view of eventually turning into a single currency. But due to (West) Germany's industrial strength, all European currencies started shadowing the Deutsche Mark, and Austria, Denmark, and the Benelux pegged their currencies with the DM. When the Berlin Wall fell, it's believed Kohl made a deal with Mitterand. France would not oppose German reunification, and Kohl will permit the creation of the Euro.
With a PoD after 1990, the most likely scenario will be after Black Wednesday in 1992 when Britain and Italy were forced to devalue their currencies. Of course Britain decided never to join the Euro. This could have led to a pause in the rush to introduce the Euro.
If the Euro was not introduced, the southern currencies would be constantly devaluing and causing complaints in the north. If Germany ends up demanding the southern countries end their devaluations (e.g. by threatening to veto EU initiatives which benefit the south), the south will experience the negatives of the Euro (no chance to devalue to retain competitiveness) and will miss the positives (interest rates will remain higher, limiting the credit boom of the last decade). Eventually the southern countries will either demand that Germany make concessions in exchange for its hard line, or they will be forced to devalue by their voters. Which means either an EU fiscal union or an exit from German-imposed tough measures.
So short answer: same problems as OTL, on a smaller magnitude.