Vehicle runs lean causes misfire

There is lots of thumping noise and vehicle idles rough.

On such cases the diagnostic codes received are P1151 and P1131.

Also the misfire Error codes will be  received.

P1151 and P1131 codes are for the O2 sensors are for lean concerns which indicate there is to much oxygen left over in the exhaust or not enough left over fuel. Normally this is the result of a vacuum leak after the MAF sensor. So the lean concern can be causing your misfire codes 0300 and 0316.



Try these test procedures:---
Run the engine cold. Spray short busts of starting fluid around all the vacuum and PCV hoses and the intake gaskets. When a leak is hit, the rpms will increase.


Also on some cases you will hear noise from intake
If you have a noise in the intake, there is a good chance it is cracked as well as leaking.

So inspect the intake manifold too.

Also on such cases the fuel pressure is important.So inspect the fuse pressure.If its very low or very high,then fuel system, parts needs to be inspected and replaced if checked weak.

The fuel system consists of fuel pressure regular,fuel pump,fuel filter and fuel itself.

If the fuel in the vehicle gets dirty,or thick,then it can cause such problems.Getting the dirty fuel replaced with good fuel helps.

Thanks,.

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2004 Ford F150: Engine Misfire and Lean Code?

Replace Spark plugs and coil but still Engine misfires and OBD code P0171 is coming up.

First check that do you smell Fuel in the cab or any thing like a fuel leak is noticed.
Also the Check engine light will flash.


The check engine light flashing means the PCM (computer) is still seeing a direct engine misfire and if the spark plugs and coils are all new then its possible you still have a problem with one or more. Start troubleshooting by removing all of them and rechecking to be sure none where cracked during install and when reinstalling them be sure to add a small dab of dielectric grease to each boot to assure there is no spark leakage down the side of any of the spark plugs. The lean code P0171 is in most cases set due to a vacuum leak and on  5.4L engine  its usually one of the ports on the rear bottom side of the intake, there is one on each side of the engine, one is for the break booster and on is for the vapor management valve. Have a look at both for signs of rotting out and leaking.

This details will help.
Thanks.

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