If you are having a misfire please enter!

Ok, so I have been dealing with my damn truck for almost 2 years... low idle, random misfire problems in only piston 6 aka P0306. HORRID gas mileage, were talking about 16mpg... well starting thursday and ending today, I have found the reason why, and its VERY common!

If you are receiving a P0301-0306 code WITHOUT the P0316 code (ignition problem) and have ruled out a bad injector (do so by checking the impedance with a DMM) then guess what time it is!?!

PULL THE HEADS! yup, on our lovely little 3.0L you will notice once you pull the heads take a gander at the EXHAUST valve seat. notice a nasty little grove? well there you go... thats the problem right there! over time and time again of opening and closing that area begins to wear and recess. The only way to fix this is by

A. Having the heads re-seated with hardened seats IF the recess is no bad enough and enough metal is left
B. Purchasing new Heads AND having hardened seats placed

also
-dont be a cheapo, buy all brand new head bolts.
-Purchase a High quality gasket set! replace all the gaskets as you go
-BEFORE YOU START THE REBUILD CLEAN THE SHIT OUT OF ALL THE PARTS!!!!!
Pictures of the recessed seats are uploading

Lastly, I know how it feels. It sucks. I hated having a truck that was running like shit. Words of encouragement, just tear into it! get the job done! all in all I spent about $550 total due to the fact that I know an individual that has been rebuilding engine at a shop for over 25 years.

-Don

EDIT: This seriously should be a sticky... I will do a solid writeup on the proces of elimination

16 mpg is far from horrid...I didn't bother to dig out my window sticker, but I'm pretty sure that about what it is expected to get when new...if you head over to www.fueleconomy.gov and enter make, model, and year, it will give you city, highway, and combined mpg projections. Mine is 15 city, 19 highway, 16 combined...
So I guess what I'm saying is that even though you are replacing your heads and that very well may have some positive impact on driveability and address your misfire issue, it seems unlikely any significant mpg increases will be coming your way.

bocefas said:

16 mpg is far from horrid...I didn't bother to dig out my window sticker, but I'm pretty sure that about what it is expected to get when new...if you head over to www.fueleconomy.gov and enter make, model, and year, it will give you city, highway, and combined mpg projections. Mine is 15 city, 19 highway, 16 combined...

Click to expand...

It really depends on the truck here. Fuel economy.gov is a nice tool, but it doesn't take the format of the truck into consideration, which can show less than accurate info. Rangers came in so many different configurations that fuel economy can vary quite a bit between trucks with the same engine.

For example, my 2000, regular cab, 2wd truck with the 3.0 and auto trans was getting 19-22 mpg on gasoline, and 17-19 on e85. It weighs around 3200 lbs. If my fuel economy had dropped to 16 mpg on regular unleaded, I'd consider that a pretty bad drop.
Of course if you take that same engine and transmission, and load them into an extended cab truck with 4wd and power everything, then it's going to get worse fuel economy because it weighs over 4000lbs now.

Anyway, back on topic, OP, I'm glad you've gotten your issue figured out. The valve seat wear isn't an uncommon problem with the 3.0 heads after 01.

I've had my 1994 b3000 ext cab 5 speed for 3 weeks. I've filled it up twice I averaged 22mpg both times. It has a
llitle rough idle. Just enough for be annoying.

bumping this for those with misfire problems

Yes the early 2000 3.0l engines had an exhaust seat issue, Ford issued a TSB for it

You should do a compression test first, a dry test and then a wet test(add oil to cylinder)
All cylinder's PSI should go up with wet test.
If low PSI cylinders on dry test do not go up as much as other cylinders then you have a valve issue, most likely valve seats in a 3.0l

This is the Ford TSB about '04-'06 3.0l engines, although it seems to be an issue back to the '01 3.0ls

Just to add there was also a TSB about the 3.0l Coil Packs on these years as well, can't find it, it had serial number range for the coils that were causing the problem of random misfires.

**************************
TSB 05-26-3

FORD: 2004-2006 Ranger

ISSUE
Some 2004-2006 Rangers 3.0L-2V "Vulcan"vehicles may exhibit:
- Malfunction indicator lamp (MIL) on with diagnostic trouble codes (DTCs) P0300-P0306 and P0316
- Rough running at various RPM
- Rough idle
- Misfire

ACTION
This may be due to an engine exhaust valve seat recession causing a loss of compression. Refer to the following Service Procedure to diagnose exhaust valve seat recession.
SERVICE PROCEDURE
1. Perform a power balance rest to clarify if a cylinder is misfiring. Identify and keep record of any cylinder that has a concern.

2. Perform a manual compression test with the spark plugs removed to locate any cylinder that may have low compression. Refer to the appropriate Workshop Manual, Engine System, General Information, 303-00.

3. If no low compression is found per shop manual instructions, proceed with normal misfire diagnostics per the Powertrain Controls/Emissions Diagnosis (PC/ED) Manual for the appropriate model year.

4. If low compression is found and it is a cylinder that had a misfire on power balance, perform a leakdown test to determine the source of leakage that may be causing the low compression. Refer to the appropriate Workshop Manual, Engine System, General Information, 303-00.

5. If low compression is found in a cylinder that did not have a misfire detected then proceed with normal base engine diagnostics per the Workshop Manual, Engine System, General Information, 303-00.6.

If the exhaust valve is identified as the source, replace both cylinder heads with the newly released service cylinder heads. Refer to the appropriate Workshop Manual, Section 301-01A.

PART NUMBER / PART NAME
6U7Z-6049-A / Cylinder Head Assembly

Mine is fixed as of about 6 months back now when i posted this. I went through countless hours of changing parts, testing the ignition system etc. When I did a compression test no cylinders had a large drop in compression but in the 130 range unlike the rest in the 155 range. I just dont want others to waste a bunch of time, keep driving on their engine, and eventually have a gutless wonder needing more than just a valve job done.

130 compared to 155 is quite a drop, just over 15%
General rule of thumb is you should see less than 10% difference

My 02 has 3 & 5 dead. It needs a head or a head rebuild. The damn truck isn't worth the cost. The motor only had 40k on it when the valves went out

buy aftermarket heads. its not a hard job. seriously... just take your time removing everything. I did it in my driveway