2001 MGM LS Misfire Codes P0301,P0302, and P0308

[Iron jaw]

Hello all,

I have all three codes and have changed all the spark plugs, the Coil Packs associated with the three cylinder codes, and the fuel filter, and idle air valve.

I still get a check engine light and stuttered performance. Feels like a power loss when driving. The car has 99,000 miles and has sat for at least three years. But was well maintained. I’ve changed the oil and filter, air filter, PCV valve, intake manifold and antifreeze. The hoses are in good condition.

I’ve taken the car for 10 minute interval drives never getting above 65 MPH. The check engine lights comes on and flashes almost immediately. There is a good amount of smoke but I’m assuming that is to be expected considering how long it has set.

I was thinking of replacing the fuel injectors for the 3 cylinders with misfires. What are y’all’s thoughts?

Is there anything that I am missing?

Thanks,
Iron Jaw


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[EaOutlaw1969]

Hi and welcome.

Did you drain and pull the tank plus flush it out? Or are you trying to burn 3 plus year old fuel?

I would have done a good compression test on all the cylinders, But before that I would have put a ounce of Marvel mystery oil down each cylinder before even trying to crank the engine over after that much down time.

Your rings could have stuck to the sides of the pistons ( soaking with oil before cranking and starting may have helped prevent damage to the cylinder walls and rings )

As far as the codes I would not worry just yet until you know you have good compression plus a clean tank with new fuel, then you can deal with the codes.

But that is just what I would start with others here may have a easier path to follow.

[Iron jaw]

2001 MGM LS Misfire Codes P0301,P0302, and P0308

Hi and welcome.

Did you drain and pull the tank plus flush it out? Or are you trying to burn 3 plus year old fuel?

I would have done a good compression test on all the cylinders, But before that I would have put a ounce of Marvel mystery oil down each cylinder before even trying to crank the engine over after that much down time.

Your rings could have stuck to the sides of the pistons ( soaking with oil before cranking and starting may have helped prevent damage to the cylinder walls and rings )

As far as the codes I would not worry just yet until you know you have good compression plus a clean tank with new fuel, then you can deal with the codes.

But that is just what I would start with others here may have a easier path to follow.

Thanks for sharing your insight! I am indeed burning old gas. It’s probably a blend of three years, 1 year, and 2 month old gas. I did run a large amount of Marvel Oil through the tank.

There is a good amount of smoke when I drive and idle as well.

Is there any serious risk to the engine when driving with three misfires?


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[Iron jaw]

Correction. The fuel was drained. So I’m running fresh fuel.


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[FordMan77]

If the light is flashing then it's likely dumping fuel into one or more cylinders. This is not only bad for the engine but will destroy the cat converters. I wouldn't drive it much until you sort this out or it could end up with more issues. The 4.6 is durable but no engine is going to take well to washing down cylinders and a bunch of misfires if driven too long/hard.

You say there is smoke. What color? Is there an odor to it? It could be stuck injectors. Also, since I don't know where it sat for those 3 years, have you taken a good hard look at the wiring harness? Could be that critters got under there and chewed up some wires. Heck, I've had mice chew through 2 injector harnesses on my DD while it was sitting in the driveway over a weekend, let alone 3 years.

[sly]

Misfire could also be bad injectors (stuck open or just leaking through - not stopping the flow of fuel).

+1 check the wires to make sure they're not torn up.

[Grand1]

Have you checked your. engine coolant temp sensor ? If thats dead it can reek havoc on a number of things.

[Iron jaw]

If the light is flashing then it's likely dumping fuel into one or more cylinders. This is not only bad for the engine but will destroy the cat converters. I wouldn't drive it much until you sort this out or it could end up with more issues. The 4.6 is durable but no engine is going to take well to washing down cylinders and a bunch of misfires if driven too long/hard.

You say there is smoke. What color? Is there an odor to it? It could be stuck injectors. Also, since I don't know where it sat for those 3 years, have you taken a good hard look at the wiring harness? Could be that critters got under there and chewed up some wires. Heck, I've had mice chew through 2 injector harnesses on my DD while it was sitting in the driveway over a weekend, let alone 3 years.

Thanks for the tips. I will check the wiring. The smoke is noticeably white but doesn’t smell like typical exhaust fumes. The odor isn’t as harsh.


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[Iron jaw]

Misfire could also be bad injectors (stuck open or just leaking through - not stopping the flow of fuel).

+1 check the wires to make sure they're not torn up.

Thanks Sly,

I’ll check the wires and injectors.


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[Iron jaw]

Have you checked your. engine coolant temp sensor ? If thats dead it can reek havoc on a number of things.

Good point Grand 1!


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[Iron jaw]

Thanks Sly,

I’ll check the wires and injectors.


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Are there any specific brands above Ford Motorcraft that are recommend?

[sly]

Not really. I use store brands and anything with a lifetime warranty that's inexpensive. I have one Duralast (AutoZone) coil on plug in my car and I know plenty of folks that use junk yard injectors to fix stuff. Usually you have more issues with the connectors not staying on the coils because they are now brittle plastic crap and like to break when you touch them. I have 3 or 4 held on with zip ties (one around the coil body for an anchor point for the other tie that goes between the wires on the harness).

[Iron jaw]

Not really. I use store brands and anything with a lifetime warranty that's inexpensive. I have one Duralast (AutoZone) coil on plug in my car and I know plenty of folks that use junk yard injectors to fix stuff. Usually you have more issues with the connectors not staying on the coils because they are now brittle plastic crap and like to break when you touch them. I have 3 or 4 held on with zip ties (one around the coil body for an anchor point for the other tie that goes between the wires on the harness).

Thanks again!


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[FordMan77]

I've always stuck with the Motorcraft stuff for my 03 Vic and so far no issues. Only had to replace 2 COPS after 200K+ miles. Never had to replace injectors but I'd personally stick with OEM if you can swing it. I did however replace the springs/boots on the coils when I did a tune-up around 120K. Just be careful when removing the injector harness clip and it shouldn't break. Yes they are likely now into the brittle "break if I look at it funny" stage so take your time. I have broken more Ford harness connections over the years due to this than I care to count even when being gentle.

RockAuto is your friend on most of those parts:

Coils- MOTORCRAFT DG508 {#3W7Z12029AA, DG540} $30.79/ea

Boots- MOTORCRAFT WR6128 {#F7TZ12A402AA} $3.65/ea

Injector- MOTORCRAFT CM4978 {#1W7E9F593A5A, 1W7Z9F593AA} $37.79/ea

Combine that with the 5% discount code and you can get OEM for far under list price.

[Iron jaw]

I've always stuck with the Motorcraft stuff for my 03 Vic and so far no issues. Only had to replace 2 COPS after 200K+ miles. Never had to replace injectors but I'd personally stick with OEM if you can swing it. I did however replace the springs/boots on the coils when I did a tune-up around 120K. Just be careful when removing the injector harness clip and it shouldn't break. Yes they are likely now into the brittle "break if I look at it funny" stage so take your time. I have broken more Ford harness connections over the years due to this than I care to count even when being gentle.

RockAuto is your friend on most of those parts:

Coils- MOTORCRAFT DG508 {#3W7Z12029AA, DG540} $30.79/ea

Boots- MOTORCRAFT WR6128 {#F7TZ12A402AA} $3.65/ea

Injector- MOTORCRAFT CM4978 {#1W7E9F593A5A, 1W7Z9F593AA} $37.79/ea

Combine that with the 5% discount code and you can get OEM for far under list price.

Thanks Ford Man! I was leaning towards Rock Auto. Thanks for the confirmation.


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