Hey everyone, My stepdaughters boyfriend has a 2000 3.0 Flex Fuel automatic with a few issues. Runs really really rough when cold but smooths out when warm, also has very little heat when up to operating temp.

The codes I pulled are P0301 and P0304. Also has P0420 for the cat. I know they're misfire codes and I'm spending tomorrow changing the coil pack, plugs and wires. Also gonna change the thermostat and both temp sensors while I'm in it.I think everything on the truck except for the front suspension we just rebuilt is original.

When I first looked at the truck the hose that connects the intake and PCV was disconnected. I had incorrectly assumed this was causing a pretty bad lean condition and causing the codes. I have checked all the vacuum hoses and sprayed throttle body cleaner everywhere. No leaks to be found anymore

The truck wasn't very well maintained by him, he isn't a car guy, I'd like to get it back to reliable if possible.

Thanks, Stu

 

Not likely to have 2 leaking injectors, but checking fuel pressure is so simple i'd go ahead and do it. If anything is leaking it will show up on the gauge when you shut the engine off
Low compression can also cause a miss fire. Should be able to spot this with a vacuum gauge.

 

Thanks, I'll have to check it today while I've got it in the garage

 

Welcome to FTE.

^+1 on doing some more diagnostics before tossing parts at the misfire & other problems just yet.

Good idea to have scanned for trouble code clues & have posted the Numbers.
Good find & fix on the loose PCV hose.

If the engine isn't heating up, I agree the thermostat sounds like it belongs on the suspect list & if faulty, is likely the cause of the poor heater performance.

Test the temp sensors for proper resistance before replacing them, as you didn't post trouble codes for them, so the computer isn't unhappy with their readings.

If the engine is properly warming up, but the heater isn't putting out much heat, touch the inlet & outlet fire wall heater hoses, to see if they're hot, or just cool. If the outlet heater hose is just cool, suspect a clogged heater core, so try back flushing it to see if you can restore flow.

If both heater hoses are hot, flow through the heater core is likely ok, so then check the in cabin "blend door" for proper operation, as it's a common problem part.

Hold off on tossing a coil pack at the misfire problem too, unless you've tested it & know it's bad, as they are usually not the problem, unless physically cracked underneath & then you can see it arc with a spray bottle of water "wet down test", spritzing suspects at idle, after dark.

If it's time for plugs & wires, 75/100K miles on the present set, or you've inspected, or tested them & know they're bad & seeing as how our Rangers have a waste spark ignition system, that works it's parts Twice as hard as the old distributor, or cop systems, by firing them on Every rotation of the crankshaft, the specified Motorcraft fine wire plugs & plug wires are recommended, as they are of high quality & designed to take the Double work load & hold up.
Seeing as how this is a "flex fuel" 3.0L, make sure you get the correct heat range plugs.

The P0420 code is for the passenger side/cyl bank one after cat converter O2 sensor saying the cat converter efficiency is low/out of range. So hold off on tossing a part at this problem until you get the upstream misfire problem put right, then see how this code goes.
If he's driven it long enough with a misfire, the cat converter may have been damaged from over heating, having to process all the unburned misfire fuel, hope that isn't the case.

More trouble shooting thoughts for consideration, let us know how it goes.

 

Thanks fellas, the tune up worked for it. 1 and 4 plugs were around .080 gap since the electrode was worn. Hoping the converter code doesn't come back since I can probably safely assume the unburnt fuel was causing the overly rich condition the rear O2 was seeing.

the heat issue was the radiator was nearly empty. I changed the thermo anyway. Like I said he's not mechanically inclined.

Now I gotta work the vibration issue which is most likely the stock u joints.

 

Ok good feedback & to hear the tune up seems to have gone well. Our waste spark ignition system is really hard on spark plug electrodes, so the newer specified iridium enhanced fine wire center electrode with platinum pad side wire, or at least double platinum designs, hold up Way longer without excessive spark gap erosion.
SO, spark gap stays in spec longer thus doesn't overwork/overvoltage the coil pack & plug wires, having to jump a worn out, out of spec wide gap plug.

The 3.0L is known to not take kindly & have head warp problems if over heated, so have him keep a close watch on the coolant level, as it's a closed system, so shouldn't be loosing coolant.

Also have him keep a close watch on the crank case oil condition on the engine dipstick.
If the head gaskets are leaking coolant & it's making its way into the oil, look for condensation, or chocolate milkshake deposit on the dipstick. If it's leaking coolant into the oil, replace the head gaskets without delay but have the heads checked for flatness before reusing them.

I agree it was probably a good preventive maintenance idea to have replaced the thermostat.

 

I forgot to add, does this puppy have the two piece driveshaft? If so & it's vibrating on take-off, it's splines might need a lube job with the new specified PTFE grease, to keep the splines free to move & happy. There is a TSB on this in the "Tech Info" thread atop the forum index page.