Idle revs or drops no matter what the situation
Not posting engine option, makes all answers, weak. all !!!
EFI system , control idle at all times. and hot it very tight 800 RPM
at all times.
there are 2 reason. (and lots of causes. over 50)
1: idle controls are dead. test them.
2: engine AFR is way lean, misfiring (bogging) or too rich misfiring .
on our USA cars, we check (SCAN IT) to see if closed loop status
happens at idle. if it dont we fix that FIRST.
if it is , then we fix ISC/IAC>
the ISC can lose control if it sticks or there are air leaks to the intake system
the first test is always to scan it , ill assume the 60,000 mile tuneup
was already done. after all why expect a bad running engine to idle correctly?
SOURCE: isuzu rodeo 2000 stalling out and rmp reving....
on 98 and up 3.2 and 3.5 v6 engines the intake gaskets are plastic.....thy crack and the truck runs rough.....listen for hissing sound or a check engine light....p0171 lean.
good luck
SOURCE: 1999 isuzu rodeo LS: Revs high sometimes then revs
Do you have a check engine light? Which engine? My 1996 Trooper with a 3.2 D.O.H.C. is awful for plugging up the E.G.R. I have cleaned it several times! Good Luck!
SOURCE: surging and dropping idle
It could be an o2 sensor. When you are unplugging your battery it causes it to rereset and loose its memory. If the o2 sensor is going out it can cause false readings leading the problems you stated. You can take it and get it scanned you can do what I did and go ahead and replace all my o2 sensors. I figured since one when out, the rest wouldn't be far behind.
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