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Bad wire in engine harness causing misfire

Recently had a new engine misfire diagnosed. Turned out it was just a loose wire that controls cylinder 2. The end of the wire that plugs into the bracket that plugs into the ECU was compromised, so I spliced in a new end of wire (same gauge) with a butt connector. There is no longer a serious virabating misfire that shakes the engine, but there is still a slight loss of power when accelerating and the car still pulls a misfire code. The car will also go back to serious shaking and vibrating randomly, but will stop just from me unplugging and re plugging the harness back into the ECU. The butt connector is very secure. Wondering if it’s a bad ECU or if splice should be soldered for better resistancy, or if it’s something else altogether. Thanks for the help.

Maybe some other connection is not so good. Can you tell by close inspection of the mating ends if there is good or poor contact? While apart, clean the connectors with electrical contact cleaner and a lint-free cloth. If some connector seems a little loose, some careful bending might be called for.

An ECU is often blamed for other more ordinary problems.

Thanks. Haven’t tried cleaner yet. I’ll give that a go. Do you think a solder would give better current? What’s strange is when I first got it diagnosed by a mechanic and he found the loose wire, all he did was put it back in and the car didn’t misfire at all or pull any codes for a couple weeks, but then it got weaker over time I guess. Which is why I ended up splicing in a new connecting end, which makes me believe that that might be the problem because essentialy the connection was better before for a while before I ended uo having to splice it.

Soldered connection with a heat-shrink cover would be the best long term…

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Thanks for your help. I’ll give it a go.

I have had butt connectors I have crimped to the nth of my strength and a month later the wire pulls out easily. Try a good solder connection.

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Heh heh. Yeah I spliced in a new injector wire on my Riv once. According to the manual, it was a black wire, but there were three black wires in the harness so I had a 30% chance. Wrong wire. Dead injector. To the shop where they fixed it right. Didn’t cost too much but my pride was hurt some.