Problem: After engine warms up, the RPM starts oscillating from ~ 1200 to 1800 rpm, about every 1 second. When engine cold ( first starts up) idles at ~ 2200-2400. When engine oscillating, the exhaust smells very rich. ECU is not showing any error codes
POSSIBLY AN INTAKE MANIFOLD LEAK CAUSES PULSING DUE TO MIXTURE VARIATION
SOURCE: 1993 chevy pickup hard starting and tach oscilates 200 rpm up and down
sounds more likley you have an air leak this will cause bad starting as it is sucking air in instead of fuel when its cold and wnen it warms up idling will be eratic and misfire check all hoses gaskets relating to the inlet manifold or if its done that kind of mileage crankcase pressure could be the problem but i suspect an air leak yates210456
SOURCE: RPM Oscillating
have you had the vehicle speed control reprogrammed if not that could be your problem
SOURCE: At startup my 94' F150 will oscillate from high to low idle
I had this problem once on an econoline van and it was the plantum gasket but before you change this check all the vacuum lines and get a digital volt meter and test the voltages on the mass air flow sensor and if you have to change the plantum gasket auto zone can print you out a diagram stating all you have to remove to replace it
SOURCE: ideling 1600 rpm onlywhen engine warm
please change the idling switch control valve assembly plus the sensor!
SOURCE: pontiac grand am 1997 V6 - rpm is oscillating
use a air gun to blow out the water inside the coils and under the coils are the ignition module
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