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Chronic Code P0305(cyl.# 5 Missfire)??

Elwood
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Joined: Mon Jun 21, 2010 5:23 pm

Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

This code appears every 200 or 300-mi. I've changed plugs, #5 twice in-case bad from stock, wire set, coil pack, even though the resistance checked good, thinking maybe intermittent, #5 fuel injector. I've wiggled the wire bundle near the PCM with the car running, trying to induce a fault. This code P0305, #5-cyl. missfire has me stumped!! Any inputs would be greatly appreciated. Thanks, Elwood

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ctrlraven
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by ctrlraven »

Sounds like it is the fuel injector. Should try and have the injector on cyl #5 tested with a labscope by a mechanic, they can test known good ones and compare the results to cyl #5.

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Elwood
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

I have a OTC Nemisys scanner that shows no faults on the #5 cyl. injector both before, & after I changed the injector. So, I doubt its the injector. The engine runs fine, so I think this is a false code, but I don't know what is inducing this false code?

Elwood
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

I've also wiggle wires attaching to the #5 cyl. injector, & have been unable to re-create this fault. This baby's a tough one! Any help?

Elwood
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

This problem is beyond your casual mechanic, I'm hoping there's a Professional Ford Mech. out there, that has ran into this issue before. Like I said, this is a nuisance message, that I would like to solve. Any help would be greatly appreciated. Thanks! Elwood

Elwood
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

An update to my #5 missfire code, it runs a little rough the first 2 or 3 minutes when cold, but after that, it runs smooth! It always starts easy! Any help would be appreciated!

ChartGuy
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by ChartGuy »

Elwood wrote:An update to my #5 missfire code, it runs a little rough the first 2 or 3 minutes when cold, but after that, it runs smooth! It always starts easy! Any help would be appreciated!
That sounds like a head gasket leaking coolant into a cylinder.

-chart-

Elwood
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

Are you thinking that when it warms up, the head gasket then seals? If this is the case, what would that plug look like compared to the good cylinders? Also, wouldn't my oil be milky? I think you maybe on to something, because this 2000 Sable runs a bit below 1/2-way on the temp gauge, where my 1998 with 210,000-mi. Runs between 1/4 & 1/2 on the gauge. I also notice that when I fill the radiator to the proper level, it drops a little ways & stays there, but never remains where it should. I guess, I should do a compression check on cylinders 4,5, & 6 while the engine is cold, & this should show a lower compression on my problem child, cylinder #5, right?

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BillR
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by BillR »

Elwood wrote:Are you thinking that when it warms up, the head gasket then seals? If this is the case, what would that plug look like compared to the good cylinders? Also, wouldn't my oil be milky? I think you maybe on to something, because this 2000 Sable runs a bit below 1/2-way on the temp gauge, where my 1998 with 210,000-mi. Runs between 1/4 & 1/2 on the gauge. I also notice that when I fill the radiator to the proper level, it drops a little ways & stays there, but never remains where it should. I guess, I should do a compression check on cylinders 4,5, & 6 while the engine is cold, & this should show a lower compression on my problem child, cylinder #5, right?
A compression check might show something but the best way to look for a head gasket problem is a "cylinder leak down test" on a cold engine.

As to your coolant issue; with a full radiator as the coolant expands it should end up in the overflow tank when the engine is hot and be sucked back into the radiator as the engine cools. There is a well known problem with a batch of Ford's radiator caps so you might want to pick up the new model. You may even have a bad hose between the radiator and the overflow tank. Even with a bad cap, from your post, it sounds like the coolant is only dropping so far and then remains stable? If so I doubt you are leaking coolant into a cylinder.

As to the gauges they are typically calibrated (more or less) to read about half at normal operating temps and they can vary a bit either way. Also if a head gasket is leaking into your combustion chamber that would tend to raise your engine temps.

Another tool you can use is swap injector from the missing cylinder to another location and see if the problem follows the injector.

Make sure you are using factory spark plugs as well, Fords don't like non Ford plugs. On that note when you pull your plugs make sure they go back in the exact same cylinder especially if you have a coil pack. If by chance you already mixed them up I'd replace them. They fire in an alternate sequence as in plug #1 fires + to - and the next one fires - to + and they get unhappy when mixed up.

Hope that helps a bit, luck man.
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ChartGuy
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by ChartGuy »

Elwood wrote:Are you thinking that when it warms up, the head gasket then seals? If this is the case, what would that plug look like compared to the good cylinders? Also, wouldn't my oil be milky? I think you maybe on to something, because this 2000 Sable runs a bit below 1/2-way on the temp gauge, where my 1998 with 210,000-mi. Runs between 1/4 & 1/2 on the gauge. I also notice that when I fill the radiator to the proper level, it drops a little ways & stays there, but never remains where it should. I guess, I should do a compression check on cylinders 4,5, & 6 while the engine is cold, & this should show a lower compression on my problem child, cylinder #5, right?
Likely not a compression issue. Small head gasket leak will let a bit of water into a cylinder. When started that shorts the plug and no fire. But in a few cycles to a few minutes the water is vaporized and the heat dries the plug and it starts firing normal.

Not uncommon but will get worse. The leak is so small no compression loss could be measured. There are tests to see if compression is getting into the coolant. However, if your coolant level drops over time, and is not leaking outside, head gasket is likely suspect. Leaks start small and grow, but not likely any in oil in early stages.

Son-inlaw had F-150 and said it would start to hit on all by the end of his driveway so he just added a bit of coolant each week and drove on. Went out of town for a week and when back, it leaked enough it was hydrolocked. No cranking. Bent a rod and terminal.

If you loose coolant a bit, and misfire on cold start, head gasket is likely.

-chart-

Elwood
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Re: Chronic Code P0305(cyl.# 5 Missfire)??

Post by Elwood »

Chart, What you describe is exactly what I have! Did a compression check last week, cylinders 4,5, & 6 all read the same. This head gasket leak is in its early stages, & not showing its self yet! I have no milky oil, only a slight loss of coolant, & a slight rise in engine temp. And like you said, it will only get worse! Thanks! Elwood