engine revving high

buhtcheeks

cheeks of the buht...
:
protege5
recently i've noticed that on startup my engine rev's really high (+2000 rpms) and backs down to around 1000 rpms after a few seconds. so i've read that this is normal...ok, then while i'm drive'n and shift back to neutral the engine spikes again and gradually drops back down when i come to a complete stop. it even feels like my engine isn't fully disengage'n when i hit the clutch to down shift, thats when my engine rev's spike. thats not normal. has anyone experienced this before. oh yeah, forgot to mention that for a day or two i rode around with my tank on "e", like past "e". could it be a clogged injector or something?
 

buhtcheeks

cheeks of the buht...
:
protege5
man, no one knows? well, the check engine light came on today, so i'll check that out maana...
 
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2001 Isuzu VehiCROSS
I've seen that happen on my Isuzu when my intake manifold gaskets went bad.. coupled with the check engine light, its most likely a vacuum leak. you can try spraying starting fluid or something similar near your hose connections and gaskets to see if you get a spike in RPMS
 

Installshield 2

Gothenburg Superiority
like mentioned, this usually occurs with a vacuum leak. There are many other causes, but that is usually the most normal. Since you got an MIL out of this, it should be pretty easy to diagnose...
 

buhtcheeks

cheeks of the buht...
:
protege5
vacuum leak found, the hose from my intake was come'n off. funny thing is its still rev'n high (slightly), the check engine light went away, but i pulled the code anyway (p0507) which is my idle control system. and it says that my engine is rev'n 200rpm above what it programmed to do. possible fixes are my pcv valve, dirty/failed/damaged throttle body, my egr valve, pr failed evap system. it won't illuminate the check engine light unless its real severe, its only over rev'n a bit. so now i'm off to check those list of things...
 
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