So I just recently had my engine retimed and General maintenance performed, I’ve had problems with misfires in the past, but nothing this…special. The car will only misfire when the engine is not warm, so if I let the car sit for a few hours and try to crank it, it runs, but with veeerry low power and extreme stutter UNTIL it gets to operating temp then everything runs perfect. I’ve had the MAF replaced last week, I’ve replaced the injectors, coils, spark plugs, fuel filter and pump, and basically everything I can think of at this point. I am getting 4 codes which make zero sense. Bank one too lean, bank one too rich, at the same time, aswell as bank two too lean, and bank two too rich. These codes shouldn’t be going on at the same time? If I let the car warm up and drive it for 20+ miles…BOOM no CEL. I am stumped on this one. I’ll provide pictures of the codes if needed
Sounds like the catalytic converter is KAPUT.
So if the cat is clogged, it’ll not run good when cold, but when warm it’ll run fine?
Its possible! Also,It sounds to me as though the temperature sensor is giving out a valid but incorrect reading so that the ECU of the car is incorrectly calculating throttle position against fuel requirements.The throttle position sensor could be the culprit.Best advice I can give you is to find a good independant mechanic because replacing parts that are still good is not the way to go.
What could explain the codes? Lean and rich at the same time on BOTH banks makes zero sense to me
Is your car burning oil? Any evidence of soot at the tail pipe or burning oil internally?
Does it run badly only when open loop?
Check fuel trims, fuel pressure, check for vacuum leaks.
It’s also possible the heaters on the oxygen sensors are not working correctly.
I wonder if coolant is getting into one or more of the cylinders and causing the spark plug(s) on the cylinder (s) not to fire. When the engine is warm, the coolant evaporates. When the engine is cold, if it isn’t too difficult, you might want to remove each spark plug and look.for coolant on the plug.
Would this indicate a bad head gasket
Unfortunately I don’t have one of those fancy computers to check this lol. Any other way?
@John_Reynolds. It could be a bad head gasket or a crack in the cylinder head or engine block. I had this problem on a 1990 Ford Aerostar. The Aerostar was still.under warranty. Enough coolant had leaked into the cylinder the cylinder wall was scored. Ford replaced the engine.
In my case, the rough running went away after the engine idled for a couple of minutes, so this may not be your problem.
Yes slightly, it’s always burned a small amount
What would explain both banks having a lean and rich code?
I’m guessing you may have an air leak specifically where the intake manifold attaches to the head. These days with plastic intake manifolds it’s a more common problem than with metal manifolds which can tolerate more torque from attachment hardware. What happens is the gasket dries up(shrinks), nut/bolt loosens slightly, or a hairline crack develops somewhere at the attachment or in the manifold proper. Plastic has a high coefficient of expansion and so a crack can leak when cold and seal itself off once it gets hot.
Try starting an ice cold engine and using a spray bottle with water spray around the manifold and listen for changes in sound and rpm.
You never mentioned the year of your vehicle. These days with anything that has an OBD port you need an OBD reader to figure out what’s wrong. I just recently bit the bullet and bought one. I went to AutoZone with a CEL, lean bank one, they told me definitely a MAF sensor, $85. Instead I spent that much money on an OBD reader, scratched my head a little and it turned out to be a dirty throttle body. $10 for MAF cleaner which I used to clean my MAF sensor, no improvement, and spray and brush the throttle body which resolved the issues the car was having.
I suspect that with the contradictory indications you’re getting that you may have more than one fault here. This is what makes an OBD reader even more essential for diagnosis.