I had a similar issue with a 93 Cabriolet, ran great for 20 minutes, then the idle changed, it would stumble and barely run. I replaced everything except the 02 sensor and never did find the issue. My european car specialist made 2 suggestions: put a Weber on it or sell it, the Digifant injection is a can of worms, he called it Digifart. I sold it to a kid who fancied himself a mechanic...

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2002 Ford ZX2
2 x 2013 Honda Civics