My Jimmy started idling rough last week. Two codes popped up on the PCM...P0171 and P0300. P0171 only showed once, P0300 stays on PCM constantly. Everything I've done hasn't worked. 130,000 miles. List below of things I've done to fix this problem, but hasn't helped.
Replaced plugs and plug wires
Replaced fuel filter
Checked all my vacuum lines for leaks, didn't find any
Cleaned my MAF Sensor
I've still got rough idling, also I notice rotten egg smelling exhaust when it is idling like this. Please Help!
I know the post is old but this is for the people who have the same problem like me and still search the web for a solution. P0300 random misfire code, rough idle after it warms up and then exhaust smells like eggs. Check the plugs 5 and 6 should have black carbon (rich fuel) plugs 1 to 4 look good. The problem was for me the Fuel Pressure Regulator. You will have to remove the air plenum to get to the fuel injector spider. Not difficult just follow a repair manual. You should notice the intake under neat will have a blackened appearance for intakes 1 to 4 and 5 and 6 will look clean. The regulator is venting the fuel and it is running down into 5 and 6 hence the fouled spark plugs. The regulator is on the back of the spider and easy to replace the biggest problem I had was getting to the fuel lines to disconnect them. Runs great now.
HI
P0300 is multiple misfires.
P0171 is lean burn on left bank 1 means drivers side
02 sensor is faulty. Your vehicle is over fuelling that is why your are getting P0300 code and the rotten egg smell. Good idea is to replace both 02 sensors.
Check the air flow sensor. and air filter, i got a feeling its one of them.
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