Hello all,

This is my first post on the forum and my first Ford vehicle.

I picked up this truck for $500 because the previous owner could not solve this misfire problem and got fed up trying to fix it (as well as it having 244,430mi on it and what looks like a leaking rear main seal..). He replaced the spark plugs, spark plug wires, and coil pack to no avail.

I've tested the fuel pressure. 25PSI at idle (gauge is a little tired; could be a few PSI higher). Scanning the computer told me that cylinders 2 and 4 were misfiring.. so I checked 2 and 4's spark plug outside the block. Sparking great. Compression was very obviously fine (from the immense amount of air pressure being released from 2 and 4), but I did not test it with a gauge. Assuming the fuel injectors were the problem, I pulled the intake hose, and the entire plastic air intake plenum to remove all 6 injectors. I cleaned all 6 by hand with Berryman's B12 and a pressure regulated air nozzle @ 35PSI to spray them through. All but one had a fantastic spray pattern.. but that one that had a bad spray pattern cleaned up after the second soak and spray. Soaked them overnight in Berryman's B12 Fuel Injector Cleaner. Reinstalled... ran like crap. This time though, the computer said 1 and 2 were misfiring. Assuming it "HAD TO BE" those two injectors were bad (as 2 and 4 were originally failing.. coincidence a bad one landed in 2 and another bad one landed in 1 I thought..), I replaced them. When I did, it ran great for about a minute until I put it in gear. Then it repeated the same crap. Computer said 2 misfire only. So, after some research, I pulled the MAF assembly out of the air filter assembly and cleaned it real good with CRC QD Electronics Spray Cleaner (I love that stuff.. anyway... off topic). I also cleaned the air intake temperature sensor with CRC QD.. as I was already there. No change at all. Then, just for the hell of it, I swapped plugs 2 and 5, erased the DTCs, and drove to the store to get gas. Came back.. light was on again. Computer now says (P0171, P0174, P0302, P0304, P0305..) cylinder banks 1 and 2 are too lean and cylinders 2, 4, and 5 are misfiring. I'm so lost.

EDIT: I forgot to mention, most of the fuel injector connectors have broken locking clips. Wiggling the connectors with it idling does nothing to change.

If anyone with more experience with the '01 4.2L V6 could chime in, I'd really appreciate it. Research tells me it could be EGR related (either the valve or the pressure sensor if there is one..?), or a vacuum leak somewhere (though it looked fine everywhere.. the gaskets on the plenum were brand new), or a friend of mine who's worked on cars for 40+ years says it could have been (back when only 2 wasn't working) a bad cam lobe... or I imagine it could be a faulty ECM/ECU/PCM/other-name-for-the-computer-that-runs-the-motor.

Thanks,
Jim

 

If you remover the plenum then you probably created a vac leak. That is where the lean codes came from. There is a torq sequence for the plenum bolts that is measured in inch pounds, and it IS important to follow it. You said it has the plastic plenum. So I think the plenum bolts are a non re-useable item, that is the biggest cause for the lean codes on the 4.2. That is if the rest of the vac/PCV system is intact. The figure "8" rubber is re-useable if it is in good shape, if it is original then replace them. Also if you over tightened the bolts you could have cracked the plastic plenum.

Before you go jumping into any other systems you need to backtrack and fix what you have already worked on.

Good luck

 

I torqued to spec (as far as I can tell. I read online somewhere that the correct torque was 90 in-lbs. they're all set that way in a zig zag pattern. I couldn't be arsed at the time to follow the torque pattern exactly). I'll check for leaks tomorrow with some carb cleaner or maybe an (unlit) propane torch to see if I get an RPM increase.

Thanks.

 

Use the unlit propane, the carb cleaner will eat parts and hoses.

Type your lean codes in the search box and look in the v-6 forum for results. You will get a lot of stuff to read up on.

 

Thanks. I'll post a report from the vacuum leak check tomorrow. My mechanic friend might have a smoke machine to find the vac leak, but since it's intake related, propane will probably be my best bet. I've never actually experienced carb cleaner eating away rubber.. but I have seen it make it brittle. I guess that's about the same result: Leaks galore.

 

Keep in mind that the PCM will react so fast you probably won't hear the rpm change. Hook it your scanner and monitor it from there, either short term fuel trims or rpm's.

Also a single cylinder misfire is probably related to the plug, wire, injector, or even a bad valve. Don't forget to check the PCV and hose at booth ends too. I hope it is something stupid and easy, good luck.

 

With that many miles on the engine, I think I would do a compression test just to see what it is.

 

I think i have something simular happening with my 08 f150 xl 4.2l 103,xxx miles computer says 1 & 5 cylender missing shakes a little in park but once under a load shakes terribly. Has very little power. Spark plugs have 20,000 miles on them changed out fuel filter witch was black nasty neighbor had a tool that lit up when touched plug wires if they were firing, they all worked. Im not sure where to go from here

 

Just a thought. Did you use any silicone gasket maker? I have a low opinion of that stuff. I use real gaskets.