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Engine shakes, cylinder 5 missfire, bank 1 and 2 too lean

When idleing it normally does all right at first but when driving at any speed it shakes and speeds up and slows down uncontrollably i bought a code reader and it says cylinder 5 misfire bank 1 and 2 are too lean could this be a fuel pump problem, ive placed a check valve in line of the fuel filter because i thought it may help and no difference was noticed, and there is no vacuum leak on cylinder 5 ive replaced spark plug, injector, and coil

Look for a crack or tear in the intake hose between the MAF and the throttle body. Rent a fuel pressure test kit from the local auto parts store and check the fuel pressure.

There are other things I could suggest but you didn’t even tell me the year of the SUV nor the engine it has so… Good Luck

I’m assuming it’s a V6 or V8. What could effect the fuel flow of both banks at the same time would be a clogged fuel filter, a failing fuel pump, or a combination of both. Mustangman is correct to check fuel pressure first. If it’s a V6 and cylinder 5 is then farthest cylinder on the bank farthest from the pump then it could be running too lean to ignite the air fuel mixture. Honestly without more information from you it’s all guesswork and everything I said could be meaningless. IMO check engine codes are relatively meaningless if you can’t look at what the various sensors are seeing. A cheap 20$ OBD2 USB connector goes a long way.

Maybe you need to determine whether or not the compression is good on that cylinder. How did you determine there is no vacuum leak on a specific cylinder? Year model and mileage might help a bit.

2001 5.4 L v8 ford expedition Eddie Bauer 4x4
200,000 miles

An Expedition with 200K… that made it to that mileage without any other preventive maintenance could suffer from many things… The first and foremost in my mind would be with the coil over plug ignition…having problems… and the intake manifold gaskets. Neither of these systems last forever and you are knocking on forevers door so to speak in regard to how long components will last.

The intake itself is also plastic… these things can crack and introduce unmetered air into the combustion mix…which will lean you out incessantly.

This is where my head would be until my eyes and ears told me to look elsewhere…just some food for thought.

Find the fuel presshre regulator. Should have a vacuum line on it. Might be under a bracket. Start the SUV and remove the vacuum line. If fuel comes out, the regulator went bad. If no fuel comes out, check the pressure with an actual pressure gauge. They can be rented at the auto parts store. Should be 55 - 60 psi

Are you sure about the psi, im not doubting you but ive read different on other websites and while started mine runs at 30psi almost constantly and ive unpluged the vacuum line and no gas

I am not sure about the pressure but 30 psi is lower than other Fords I’ve worked on. When you remove the vacuum line did the pressure change? It should have. You should also drive the car and see if the pressure holds under load.

No it didnt and ill see about driving it if it changes

If anything it rose and droped and the vacuum line on the regulater didnt seem to be pulling a vacume on it

Can u recomend a reliable place to find the corect psi

A Ford service manual… Mitchell repair guide online. They have subscription fees that are pretty reasonable. Google is your friend.

The 2001 5.4L Expedition should have a Mechanical Returnless Fuel System (MRFS). In this system, the fuel pressure regulator is part of the Fuel Pump Module in the tank. The fuel pressure should be in the 35-55 psi range.
In an MRFS, the thing on the fuel rail that has the vacuum line is a Pulse Damper, which reduces fuel system noise caused by the pulsing of the fuel injectors. It has nothing to do with fuel pressure regulation.

Oh ok so my best bet is to get a fuel pump


First, clarification is needed. My info above regarding the MRFS was based on the 2001 Powertrain Control/Emissions Diagnosis Manual (PC/ED). However, I just noticed that the 2001 Expedition Workshop Manual shows a return fuel system with the pressure regulator at the fuel rail. In other words, the two manuals give conflicting info. Does the thingy on the fuel rail with the vacuum hose on your engine also have a fuel return line attached to it? If so, it’s the regulator. If not, it’s the pulse damper as mentioned previously. For a return-type system, the fuel pressure should be in the 30-45 psi range.

Have you yet checked the voltage at the fuel pump and/or the condition of the fuel filter? Or done further diagnosis for the misfire, if it is still happening?