P0303 Misfire on Cyl.#3.....Help Please

[Gr8Stang]

Hi All,

Was enjoying a nice ride in the old girl today (98 Cobra) on my way to hit a few balls at the driving range when all of a sudden she started to run rough, and down on power. Put the ODB on her tonight and the P0303 was the only code....which would seem to jive with the behaviour.

Just looking for any wisdom you guys have on the best way to go about troubleshooting it. From the little I've read, sounds like it could be plug wire, coil pack or plug, or maybe even a bad injector?

Since she's celebrating here 20th b-day this year and has the original plugs and wires on her, probably not a bad time to replace those anyways (118K kms on the odometer).

Thanks boys!
Scott

[Ponyryd]

Pull #3 plug for inspection, if it’s wet with fuel then you have an ignition problem, meaning bad coil or wire.

[Gr8Stang]

^^^ Thanks. Just ordered a set of new plugs and Ford Performance wires. Figured it's a good time to get her refreshed....she doesn't owe me anything.

[ZR]

It needs plugs n wires regardless, solid place to start.

[Gr8Stang]

It needs plugs n wires regardless, solid place to start.

Yep, ordered them and hope to get at it this weekend. The plug wire routing looks like fun to tackle. Hoping the plastic wire separators survive the task.....and will still working with the new Ford Performance 9mm wires (believe the stock ones are 8 mm)....

[Gr8Stang]

Installed the new FRPP wires and motorcraft plugs in the sweltering heat today and she's back running better than ever!!

The plug in cylinder 3 had the distinct strong odor of gas, so I guess the plug wire gave up the ghost.

THanks again for the input.

[ZR]

Best of news, enjoy.

[RioCobra]

Funny I just did the exact same thing on my 97 cobra today, damn was it hot.
Did all of your wire clips survive?

[Gr8Stang]

Funny I just did the exact same thing on my 97 cobra today, damn was it hot.
Did all of your wire clips survive?

Haha! For the love of our rides. Those clips were a royal pain, and were going to be to small for the FRPP wires, so I cut most of them open and discarded them. I reused the rubber ones closest to the valve covers. I also left the lower half of the clips that run along the top of the alternator and snugged in the wires. I'm going to purchase a couple more 4 wire separators just to clean it up a bit further. I'm happy with the look of them.....and extremely happy with how the car runs.

[RioCobra]

I just took the car out for a 3 hour back road rip before it got to hot today.
Car ran perfect.

One of my clips on the alternator was missing the top part before I started, but the rest I was able to open without breaking them.