Hello Everybody! Im new to the site and im in desperate need of your help. I own a 2000 Honda Civic Si with K&N Intake. Recently i have been having a issue with the vehicle. When I start the car and let it fully warm up its fine, but once i start driving or just let it sit running, the rpms will increase to 1000-1100. On top of that, when it does this, the car will not engage vtec but after a couple minutes it will stop, idle at normal rpm and vtec will work. I have been at this for 2 months and its driving me insane. It has a new iac motor, vtec screens have been replaced, selonoid has been tested, tachometer works fine, vtec oil pressure switch is new, oil level correct. I have not replaced the tps, map, or coolent sensor. I know how the vtec is suppose to operate, so im not expecting more than i should nor imagining things lol. Just need some friendly advice to hopefully fix this issue. Also i have not replaced ecu.

 

Check engine light? Is it revving to redline?

 

I wish everyone had a chipped ecu with datalog...but since we don't, it's obvious something is causing it to idle high and it's likely that's causing vtec to not engage as well.

Do you have A/C? A/C can cause it to idle up but I don't see it affecting vtec. You say your vtp is new but if it doesn't get engaged no vtec, are you sure you have good oil pressure?

Vacuum leaks could also cause a high idle. Check for codes?

 

No cel, checked vacuum lines, and i dont use ac lol. When it starts to act up, it just sits at 1000 rpms and vtec wont engage until whatever is going wrong fixes itself. Its intermittent but only when at full operating temperature. Could this be a tps?

Yes, it will go to redline.

Now here is where ill pick your brain, with the engine idling, i unplugged the iac motor. Rpms will drop super low, once the cel comes on, it will rise back to 900-1000. Ill turn the car off and erase the code, start it back up and its perfect. I also did this with the tps and the exact same thing happened. No idle issues and has vtec. Could they be acting faulty with no cel?