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2.9L & 3.0L V6 Tech General discussion of 2.9L and 3.0L V6 Ford Ranger engines.

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Old 12-02-2015
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Location: North Wilkesboro, NC
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truck will turn over but wont run

2004 V6 3.0 will spin over and fire but runs rough. I hooked a code reader to it and gained P0300, P0304, P0305, P0306, and P0316 as codes. have changed the coil pack and fuel pump and still no change. any suggestions?
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Old 12-02-2015
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Unfortunately there is a TSB about those codes on the 2004-2006 Rangers with 3.0l
TSB 05-26-3

FORD: 2004-2006 Ranger

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

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.
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.

6U7Z-6049-A / Cylinder Head Assembly
It may not be this issue, a compression test on all cylinders would tell you alot.

The heads in these years, and I think 2003 as well, had faulty exhaust valve seats that would recess into the head lowering compression and causing misfires.
As far as I know machine shops can install new hardened valve seats to repair the heads.
Under warranty Ford just had dealers replace the heads because they don't generally send parts out to machine shops, but you can and it would be the same fix as new heads but cost much less.
The heads were not bad, the exhaust valve seat, which is a removable/replaceable part, was the bad part, all 6 should be replaced.

Last edited by RonD; 12-02-2015 at 07:30 PM.
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Old 12-02-2015
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Join Date: Dec 2015
Location: North Wilkesboro, NC
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it wont run long enough to even do a compression test itll sputter and run like its lost about 2 or 3 cylinders
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Old 12-03-2015
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You remove all the spark plugs first and then test one cylinder at a time with a compression gauge in spark plug hole.
All spark plugs need to be out so you can get good crank speed from starter motor and battery.
You need 4 or 5 "hits" of compression stroke to get accurate reading.
Write down results then move to next cylinder

After all 6 are tested remove highest and lowest number, then add up the other 4 numbers and then divide that by 4, that will be your Average compression number.

Divide that number by 10, that will be 10% of average, and any cylinder that is lower than 10% of average has a problem

There is no "running of the engine involved"

Say you got
#1 = 165
#2 = 130
#3 = 155

#4 = 160
#5 = 155
#6 = 135

You don't use 165 and 130 at this time, highest and lowest
Add up the rest.
155 + 160 + 155 + 135 = 605
605 divided by 4 = 151.25

10% is 15.12
151.25 - 15.12 = 136.13

So any cylinder below 136.13 has a problem
That would be #2 and #6, but thats pretty easy to see without all the math, lol.
If you have 2 or 3 cylinders testing at 160 and the others below 140 then averages won't help much, my guess would be valves at that point

Low compression cylinders should be retest, then test again "wet", wet test is when you add a teaspoon of oil to cylinder via spark plug hole, I use a straw, dip it onto oil bottle then put finger over the end and lift it out of the oil and place straw into spark plug hole and remove finger.
reinstall compression gauge and retest
compression number will go up, but how far up will tell you if it is Rings or Valves that is causing the low compression.
If it was 130, and goes up to 140 then valves are the issues, if it goes up to 150 then rings are the problem.

And compression numbers are not about the exact number, i.e. higher than 150, compression gauges are not calibrated to exact standards, lol, unless you pay to have that done, and batteries and starter motors are not all equal, so crank speed is a factor.
If you are getting 140 as the highest and 110 as the lowest that is fine, test all cylinders, the point is the comparison of the numbers, they should all be equal or within 10% of each other

Last edited by RonD; 12-03-2015 at 11:29 AM.
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