Im throwing a missfire code in Cylinder four and Bank 1 is running lean.
It all started when I replaced the stock air box with and aftermarket cold air intake. This through the misfire code.
It only used to missfire on idle but when driving youd never notice it. Now when i get on it hard, you can really feel it missfire and it jumps on ya. I replaced the spark plugs, two of the coil packs, and the back O2 Sensor. I also put CFoam through my fuel to clean out the injectors and pulled the injectors to cleaned them.. It stoppped missfiring while driving it hard for awhile.. and it drove great but it still would missfire on idle. I dropped my car off at the mechanic and thats when he replaced the back O2 sensor.. and I got it back and its missfiring worse than ever now. Still cant figure it out.. I checked for a vaccum leak and didnt find out..
My thinking is...
MAF Sensor
Bad Injector
Clogged Injector
Weak Fuel Pump
Any Ideas?? I really need to get to the bottom of this and get it fixed!
Well, you always start with spark plugs and wires. But rather than throw out all the possibilities, why don't you tell us what you've done so far and the year, make, model, and engine. Kinda important info you left off.
Year, make, model, engine size, mileage?
The single most common cause of a misfire at idle is low compression, do a compression check. If you get lucky and you don't have low hole then it's very likely you have a vacuum leak or bad injector at the cylinder identified by the code...
o2 sensor?
