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Hey guys, i ran into this a couple times and i am hopeing someone knows whats going on, i have an 01 EX 5spd, it had a bad motor when i got it so i put and 01 EX motor in it with 40k on it, now for awhile it ran weird, it wouldnt die out, but would idle at around 2000, then a few seconds later would drop to about 1500 and bounce from about 1500-1700, then after it did that a few times would go to 1000, for a few seconds then go to regular idle, now i kept driving it and redid the ground caples and it seems like it was fixed, not i just put a new battery in it and its the same way, i check the grounds, and reset the idle that i found searching on here, and it still does it, im wondering if it still could be something up with a ground, or does the computer fully need to reprogram to run right, after reseting the idle it didnt change so im not sure here, any ideas would be great, also im wondering if this has anything to do with my lights dimming problems, whenever any thing gets turned my headlights dim, just wondering, thanks

 
Rep Power: 424

Can check the idle air control valve, and the igntion, that would be a good start. Make sure everything is working right. Do you have codes?
The lights are dimming because the power is fluctuating so the alternator speed isn't keeping up with the power demand. Check all your electricals while you're at it, just in case something got messed up in the motor swap. Regardless, the idle, if those RPMs are on a warm motor, are excessively high. The car should idle in the 700-800 rpm range when warmed up.

If the cycle you describe is from a stone cold car, then yes, it will idle high until it warms up a little, then drop. if it holds steady at 700-800, then start considering the alternator as your light problem.

 
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its when its warm, i know cars well, but am new to the civics, i just did all the grounds , and it runs good, and sometimes will idle where it should be, i have no cel or any code, just idles odd

i wanta do that idle air control cleaning i keep seeing people talking about but cant find any info about it

 
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take off the throttle body, and remove the piece that the coolant hoses go into. spray carb cleaner inside until all the black goes away. reinstall, and do the idle learn.

 
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cool, i will try that today, thanks

 
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All i did when i had this exact problem with my swap is disconnect the battery for a minute and the problem went away.

 
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well it started an starts anytime i disconnect the battery, anyway looks like it fixed itself, a few days of driving did it, thanks for all the feedback