My 01 Elantra 54k miles is surging from 1500 rpm to about 4000 up and down non stop. I had to undo and splice the wiring harness under the left fender to do a body repair. I was very careful to solder and get the wires back to normal [all 25]. As far as I can tell none of these have anything to do with the idle. The car ran fine when I parked it. I dont think any thing just spontaniously broke on its on. What could I have done. Or what controls the idle. Wiring diagram would help.
Posts: 33
Joined: 8/27/2004 From: Australia Status: offline
HI,
Perhaps the first thing I would do is reset your ecu.
Removing power from the ecu will reset it back to factory default. I had a similar problem although mine went up to about 3000rpm and down to extreme shuddering.
Leave the fuse out for about 5 minutes and reinsert it.
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idle surge - 
