Rep Power: 0

My 98 civic idles fine until it warms up. Then it runs 1500 rpms then bounces up to 2000rpms. 1500 then 2000. up down up down. there are allot of custom parts on the car. cold air intake. vtec kicks in at 5300 due to a chip. fuel pressure regulator. just to name a few. the car runs well. fires on all cylinders. funny thing was it always idled lower than normal. now its spiking back and forth. very frustrating. No engine lights are on. I dont see or hear any vacum leaks.

Please help!

Thanks!

 
Rep Power: 236

Check for vacuum leaks. Clean the IACV and throttle body.

 
Rep Power: 0

Possible intermittent coolant temp sensor or even unbled coolant. Had this problem with mine. Only fluctuated during warmup randomly. Does it ever calm down and finally idle ? or is it idling over and over in that range you mentioned? Is it happening in drive ? or only park?

Have you done anything recently that would have caused this? if so think about that.

 
Rep Power: 0

Aikl;k;/

 
Rep Power: 0

that used to happen to me but rather than doing a whole bunch of crap, my friend took a screwdriver and tightened a screw some where on the engine and it all stopped.

 
Rep Power: 0

Well case closed, hands down everyone. Tightening a screw on an engine fixes all idle woes.