I had a Smog test in California on my Dodge Dakota Truck 3.9L Engine. Because of high NOX, it was at 15 on the MPG test portion.
The mechanic said it needs to have the injectors cleaned. What is your take on this? All other parameters of smog test passed.
NOX is the result of higher than normal cyllinder temperature. Usually, this is related to an EGR system not functioning properly. If the car is running to lean from a clogged injector, this could cause an increase in NOX. If the cooling system is not functioning properly or the fan is not coming on, this will also increase NOX.
〉 Answered on Oct 5th, 2013 by Helaine Kurot, Owner/Technician at 360 Automotive
You have have carbon build up in your fuel system, that after cleaning, can raise MPGs.
〉 Answered on Oct 5th, 2013 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
Your mechanic is probably right. clogged fuel injectors reduce the amount of fuel getting to the cylinders, thus causing too high air to fuel mixture which would cause high NOX.
To help keep the fuel injectors clean, buy high quality gasoline (use a well known name brand like Chevron or Shell) they have detergents to keep your system clean that cheaper gasoline does not have.
〉 Answered on Oct 5th, 2013 by Colleen McGee, Driving Instructor at Americas Driving School