Rough Idle & Flashing CEL

[shadowless127]

I've been getting a P0442 code for the past couple weeks. I attributed that to the original gas cap with seals that were just toast after yaers of use. I replaced it iwth an autozone aftermarket and cleared the CEL and all was fine up untill wednesday when it came back. After examining the replacement cap I got at autozone, it looks like a pretty cheap unit that possibly doesnt adhere to ford standards therefore tossing a code. Code came up about 15miles after a refueling.

Today I'm on my way to work and as i'm right around the corner the truck starts to idle rough, then about 20ft from my office driveway the CEL starts flashing. Keep in mind the CEL was already on from the P0442 i kept forgetting to clear. I did get on it on the way to work today (didnt exceed 3000rpm).

The acceleration seems fine, everything else seems fine as well except for the stupid 5.0 tick under load. I don't have rotten egg/dying cat converter smell, no fluid leaks, etc.

Could this be a clogged fuel filter?

I wont be able to get the codes read till lunch.

 

[duke16]

Flashing CEL = misfire.

 

[shadowless127]

Flashing CEL = misfire.

What would cause a misfire?

 

[duke16]

When they CEL came back on after replacing the gas cap, did you verify it was the same code?

First thing I would do is get the CEL checked out again and see which cylinder is misfiring.

Possible causes could be wire, plug, injector....

 

[shadowless127]

after doing some reading it seems like it could be a bad o2 sensor.

Gonna go to autozone on my lunch break and get the codes pulled.

 

[shadowless127]

Just got the codes read

P0442 (as expected)
P0307 - Cylinder 7 misfire

what's the next step for the misifre? Plugs and wires are new, less then 12months old.

 

[sport97]

If i were you, first thing i would check before spending any money is the plug and wire for cylinder #7 to make sure they are still in good condition. Sometimes the wires melt against the block or get a nick in the rubber causing it to short, making a misfire.

 

[duke16]

Agreed. I had new plugs, and it turned out the ceramic on one of them had broken... it wasn't until removing it the second time did I finally see it was loose.

 

[shadowless127]

If i were you, first thing i would check before spending any money is the plug and wire for cylinder #7 to make sure they are still in good condition. Sometimes the wires melt against the block or get a nick in the rubber causing it to short, making a misfire.

I did a quick inspection of the wires before I came back from lunch and they are in good condition.

How would one detect a bad coil pack assuming the spark plug is in good shape.

 

[duke16]

How would one detect a bad coil pack assuming the spark plug is in good shape.

Multimeter. There's a thread somewhere that explains the procedure I think.

 

[ThePhoenix]

couldnt a clogged injector also cause a misfire in a cylinder?

 

[shadowless127]

couldnt a clogged injector also cause a misfire in a cylinder?

yes.

I've been running high grade exclusively for the past 2.5 weeks because the car seems to run better and i get better fuel mileage with it.

This wouldn't have clogged an injector would it?

also, iirc a clogged fuel filter can also cause a misfire... can anyone confirm this?

 

[ThePhoenix]

I can confirm that one. yes, clogged fuel filter will starve an engine and can cause misfire at higher rpm's

 

[shadowless127]

I can confirm that one. yes, clogged fuel filter will starve an engine and can cause misfire at higher rpm's

Ok good to know.

Also, how would I go about cleaning the injector?

 

[ThePhoenix]

i have a "lean" code right now, which could be a clogged injector or a bad catalytic converter, or a gasket leak. I am going to run a can of seafoam thru the gas tank. If it IS a clogged injector, that should take care of it, I hope

 

[duke16]

I can confirm that one. yes, clogged fuel filter will starve an engine and can cause misfire at higher rpm's

If it were a clogged fuel filter, I would expect more then 1 cylinder to have a misfire.. but I could be wrong.

 

[duke16]

Also, how would I go about cleaning the injector?

Injector cleaner would be the first step.

 

[shadowless127]

Injector cleaner would be the first step.

whats the best brand to go with?

 

[shadowless127]

ok some new discoveries on the way home. The firs five minutes of driving, no misfire, no rough idle. Then i get the flashing cel and it starts idling rough. Get on the freeway and keep it 1900rpm and below. For the first half of the trip I noticed that if I wasn't on the gas I felt a little bit of a stumble from the misfire; if I was on the throttle it runs smooth. I get off at my exit and i notice that while it's still idling rough it's not idling AS rough. I get home, turn off the engine sit for 15seconds, fire it back up and we're back to idling normally.

Im gonna go pick up some STP Fuel Injector Cleaner and hope that works.

 

[shadowless127]

Seems to be the misfire happens when I hover over 2100rpm for more then a couple seconds.