Changed plugs and they were all good...changed plug wires too...replaced coil pack and it was good...has a bad rough idle dropping below 1000 rpms.....cleaned mass airflow sensor....throtle control sensor works fine....idle control sensor will cause the engine to die if unplugged..Could the idle control sensor still be bad....
You have to correct the cylinder misfires first
You may have vacuum leaks somewhere in the
intake or exhaust
You really need to look at data with a scan tool
You start with Mode $06 & cylinder misfire count ,if that
even works well on your motor
Then you look at fuel trim & add short & long together,
to get an idea if it is running rich,which would be a lean
condition from a vacuum leak or rich from leaking injectors
All the data is only good if you haven't cleared it or disconnected
the battery. If you did, then you have to drive until all I/M Monitors
run & then look at data
You look at O2 sensor data & even scope them
You made no mention of checking for codes
No mention of a cylinder leak down test for valve leaks
Exhaust Converter age or condition !
Fuel Pressure !
SOURCE: p0301 trouble code
The misfire is detected by the misfire monitor as a slight change in
engine speed which the PCM calculates back to a particular cylinder.
The monitor is active continuously, but associates problems into 3
types. Two of the types are monitored on successive trips. The first
trip the monitor detects a misfire it sets a pending code but not the
MIL light. If on the second trip the same problem occurs the DTC code
is set as current problem and sets the MIL light on. The MIL will stay
on untill the DTC is deleted. The remaining type is a most sever case
and signals the possibility of cat damage. In this case the misfire
monitor identifies the problem and the PCM determines it to be severe
and immediately sets the DTC as current and the MIL light to flash at a
rate of 1 per second until the condition is no longer present, at which
time the MIL stays on steady.
So once the P0301 is set it never turns off, except by code deletion procedure.
I think a lean burn condition could cause a misfire, but probably not
from a PCV problem which should affect all cylinders equally. There
would likely need to be another problem with that cylinder or intake or
...... .
SOURCE: 2000 hyundai sonata.. P0300, P0110 and P0102 codes..
Higher octane gas 93 with some good octane boost in the black can at autozone cost about 7 dollars or a bottle of 104 octane boost. Change the fuel filter. Probably only one coil pack is bad. The OBDII reader should tell you which one was a misfire.
SOURCE: misfire in cylinder 3
NO to the MAF Sensor Question, and Spark Plug Wires Or BOOT Will Cause Missfire. As For Mass Air Flow Sensor Easy Check is to Dissconnect it While Engine is Running And If ENGINE SMOOTHES OUT The Sensor is Bad
SOURCE: I own a 2002 Chevy Trailblazer with 4200 vortec
Do you know if the plugs were changed, a bad or broken plug will also cause rough idle and slow acceleration?
SOURCE: rough idle. rpms drop. misfire.
try your coil packs they go over your sparks or do plugs first and see what happens do affordable first
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