I have a problem I've been chasing and It is driving me nuts.

The engine started with a simple misfire, which turned bad 7 mile into my 15-mile drive home. I completed the checklist below with good results until now. I can drive at a steady speed but when I have to do a little acceleration the engine will give me what feels like a continuous misfire. I back off a little and it levels out. The only thing I have not change yet is the fuel filter.

- Check Engine Light on - Error code ? - Misfire #4 Cylinder
- Replaced all spark plugs
- The truck ran fine.

- Check Engine Light on - Error code ? - Misfire #4 Cylinder
- Replaced #4 Spark plug
- Replaced #4 Spark plug Wire
- The truck ran fine.

- No error code: Rough running at approx. 30-40 mph under accel.
- Replaced Ignition Coil pack
- Replaced all Spark plug Wires
- Added a bottle of Dry gas and Fuel injection cleaner.
- No improvement

- Next 2 steps are to replace the Fuel Filter and then the pump.

Any help would be greatly appreciated

 

i would try the fuel filter and take out your fuel injectors let them soak in cleaner over night clean em out and reinstall and dumb question but ive got to ask but how are your plug gaps? are they set correctly also check engine grounds maybe you have a bad ground somewhere

 

also ive heard on some vehicles with the check engine light on throwing that code changes the air/fuel mixture try reseting the ecu

 

hows the water level in the radiotor?? just wondering if you checked it. most the time on a 4.0 with a cly 4 missfire has to do with a cracked head are head gasket. water is geting into the cyr fouling the plug out. i had the same problem a few years back. same problems your having i finaly broke down and tour the motor down and replaced the damaged head. and she runs like a champ.

 

Radiator level is good. I checked the #4 plug when I changed the remaining wires and coil pak, it was good. Since my initial post w/dry gas & injection cleaner, the miss has disappeared. Fuel filter is being replaced and I'm looking at checking the fuel pressure at the valve on the injection rail. Thanks Crossing Fingers

 

run some seafoam through it, clean it out real good.

 

Update: I replaced the fuel filter and ran a can of sea foam through the engine. The miss has shown back up. I checked the radiator and noticed it down a little. I added fluid to both the radiator and the reservoir. Confusing…now the error code is showing misfire on #6 cyl. with new coil pak. Blown head gskt. I don’t know. I found the date on my last head gasket R & R, 5/14/08. 2 years and 5 months between jobs…I don’t think so.

I love troubleshooting but I’m running out of time with weather and I can’t drive the mustang in the snow. Time to BTB and take it to a shop.

 

time has nothing to do with a part going bad...its the mileage and how the truck is driven

 

Almost seems like a phantom problem. I have been throwing that code for awhile in my 04, and on cylinder 4. Only throws the code every 2-5,000 miles, and especially when its hot out and at idle. I stopped chasing the problem. I literally just delete the code with my programmer in the truck every time it pops up. Hopefully that method doesn't bite me in the ***.

 

Not a phantom more like a bronco bull when it happens. Sent it to the analyzer machine today. When they connect the system it is providing incomplete data. Mechanic says it may be the computer or a cracked wire in the harness.

 

If you just replaced the head gaskets then and not the heads also I would almost bet on a head being cracked.... VERY common in the 4.0 OHV....had it happen on my '99 and went through the procedures you have done until retired ford mechanic convinced me to pull the heads. And it has nothing to do with how the vehicle has be driven/treated, just faulty castings from the factory. Buy the new redesigned heads and all will be well from here on out.

 

Update: We tossed in the towel and finally took it to Ford. Carbon tracking on the spark plugs, also found the auto parts store sold me the wrong plugs, not Dbl. Platinum. Runs like champ. Thank everyone for your help

 

Gotta love the auto part store screw ups