2008 Ford Explorer misfire.

110

Asked by GuruD5CSK Aug 10, 2017 at 06:14 PM about the 2008 Ford Explorer XLT

Question type: Maintenance & Repair

I have a 2008 explorer with a 4.0. I recently purchased it for my daughters college car. I knew it need some work but didn't expect to struggle to fix like I have.
Misfire codes P0306
Replaced the following:
Spark Plugs
Plug Wires
Coil
ECM
Intake Gaskets
I'm at a loss and have thrown enough parts at this thing.
Thanks in advance for the help!!

36 Answers

Did you clear the code after replacing all those parts?

3 people found this helpful.
22,240

Have you looked at fuel delivery? Fuel psi? Injector on cylinder 6? Leak down on cylinder 6? Compression on #6?

1 people found this helpful.

Definitely check the compression before throwing more parts at it.

3 people found this helpful.
110

Yes. Thanks for reminding me. Also replaced #6 injector, compression and leak down test. Also checked all wiring back to the ECM

1 people found this helpful.

You could try swapping out parts to see if the trouble stays at #6 or moves with the part.

2 people found this helpful.

I know this probably has nothing new for you but if it helps you then great ------ https://www.yourmechanic.com/article/p0306-obd-ii- trouble-code-cylinder-6-misfire-detected-by-jay-safford

22,240

Any vacuum lines or pcv close to this cylinder? We're all your psi readings in spec? Borderline can cause issues. Any arcing inside plug well on #6?

1 people found this helpful.
22,240

Did you put on a new O-ring on new injector? All of them? You could be losing psi on dry O-rings

Buying a device that hooks up to the OBD2 port that gives you live data might be the next step. Something like this ----- http://www.auterraweb.com/

1 people found this helpful.
110

To further explain. The misfire code PO306 was stored, the engine light is on at idle, and while driving the engine light flashes. It has a rough idle and extremely rough in OD at highway speeds.

22,240

Flashing light is bad. It means that you are in jeopardy of ruining your catalytic converters if driven like this. Raw fuel getting down that far without being burned. Yes buy a live data scanner to monitor different systems. Harbor freight has a cheap one but autel is a good brand. I have 2 autels and a harbor freight one. Any O2 sensor codes?

2 people found this helpful.
Best Answer Mark helpful
110

Live data device it is. I will get one ordered. What exactly should I look for as far as data? Thanks F_O_R & Guru9FSV8. If y'all think of anything else please let me know.

110

It had no lean codes or O2 codes. Just Random misfire P0300 and #6 P03006

1 people found this helpful.
110

Any thoughts on it being an issue with the crankshaft sensor?

1 people found this helpful.
22,240

P300 is almost always fuel related! Look at short term and long term fuel trims and oxygen sensor activity with engine at operating temp. There are a lot of good YouTube videos on how to read live data and misfires. Wells automotive has good ones

4 people found this helpful.
22,240

Almost sounds like a good sized vacuum leak causing you ECM to overcompensate and pour in the fuel...hence the flashing check engine light and unburned fuel getting downstream.

1 people found this helpful.
22,240

Using fuel trims to determine type of misfire by scanner danner on YouTube is a good video. I want to say gasket leak. You said you replaced manifold gasket. Are you sure it sealed? Fel Pro gaskets are good. This goes along with vacuum leak like I said earlier

3 people found this helpful.
110

Ill check it out. Yep, I even pulled the intake back off to verify. Everything looks good. When I get the live data scanner hopefully some questions will be answered.

1 people found this helpful.

A flashing light on Fords means that a code is pending at least on the two I own. I would look at fuel trims like others have already mentioned. One possible source of a hidden vacuum leak may be behind the battery box. On my Fords the vacuum tank is on the back side of the battery box next the the fender and on my F150 the vacuum hose rotted off at the tank which is totally hidden from view.

2 people found this helpful.
90

Oh man, I have exact same symptoms but on cylinder 2. Replaced spark plug, spark plug wire, gnition coil pack and fuel injector. Mechanic thinks it's pcm. He said he checked wires from pcm to fuel injector. He said he ran multimeter on fuel injector leads and could see it losing signal periodically. Did you ever get yours fixed???

3 people found this helpful.
110

Yes. After throwing a bunch of parts at it I finally figured it out. That was two years ago and she has been driving it ever since with no issues. It turned out to be a broken valve spring. $5.00 part

5 people found this helpful.
90

May God shine kindly on you, sir! I pray that's the same for me... I'll find out this weekend? Was it difficult to change out? I've never been that deep in an engine before. Plenty of YouTube vids though...

90

For others experiencing similar issues... I did and do not have a broken valve spring. I did find the connecting wires to my EGR had a spot where all the wires sheathing was worn off and those wires were touching. I fixed that. I replaced my EGR and cleaned my intake. While doing this work my battery cable was disconnected. I drove many problem free miles over the next couple of days. However, slowly but surely the problem re-arose. Its very odd. It makes me think it's something electronic.

1 people found this helpful.
10

I have a 08 as well same issue misfire cylinder 2 replaced coil pack plugs wires infectors seals all kinds of things are brand new problems still there they seem to think it might be an exhaust leak causing air to get in somewhere if you guys figure out the problem please I'm desperately trying to get this fixed

90

It was my ECM. Dealership replaced and flashed and the problem completely went away.

10

Was it very expensive I just bought the car yesterday and it has that issue right now and I can't seem to figure out what to do

1 people found this helpful.
10

So I took mine to the ford dealership they said the timing is off on both timng chains said I might as well replace the motor for the same cost

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