Random misfire

Hi all, I am helping a friend who has a 2004 Ford Expedition EB 4x4. It has 123000 miles and manufacturer's recommended maintenance was followed. Last tune up was 2013 for the 100K maintenance by the dealership. Last oil change was January 2018. The truck is experiencing what feels like random misfire. Sometimes while on park, moving slowly or stopped at a red light, you can feel the engine shake momentarily and sometimes it just doesn't do anything. It does it too while backing up. It picks up speed and brakes well. No problem starting either.

The coils and plugs were replaced on 2013. Check engine light came on December 2017 with lean and misfire codes. Misfire includes P301 and P305. Replaced pcv valve and hose to intake. Hose to intake rotted out. I know a lot of things can cause this but just in case anybody had a similar experience. Checked other vacuum hoses with carb cleaner, didn't find anything. I am thinking of cleaning the fuel system. Is it safe to use Seafoam on Expeditions? Will be checking the plugs and coils next.

Your codes indicate a misfire on #1and #5 cylinders, as we've stated before swap that cylinders coil, with the one next to it, see if code moves to that cylinder. If it does you now know you'll have to replace that coil. If you have any coolant leaks above those cylinders, repair first. If the coils don't change code, try replacing those 2 sparkplugs. Let us know your findings.

Sent from my N9131 using Tapatalk

Swapped the coils per above and reset check engine light (CEL). Drove around for a while, no CEL yet but I can still feel the engine misfiring as described before. What are the cons of driving around with a misfiring engine?

A misfiring engine on computer controlled catalytic engines is never a happy ending. Your codes are misfire, not lean, so you want to concentrate on secondary ignition, spark plug, coil, coil boot, connection to coil, make sure their not corroded, fuel delivery, power to injector, and pulse, fire to those cylinders, and lastly engine itself, valves, piston, compression, on those banks. You can try sea foam or one of the stronger ones, see if any change, usually most either don't work, or are very minimal when you get to a driveability issue stage. Keep us posted what you find.

Sent from my N9131 using Tapatalk

You didn't check fuel pressure.

Ran into to this issue. Imo the better coil packs are motorcraft oem. Some can fail in a very short time. Shop around for oem and do not mess with driving it with a miss fire. You can create a hot spot on piston running it lean or on a true miss and blow a hole in a piston. Get it fixed quick! No long trips. You are ahead of the game because the computer told you which 2 are bad. Even go to a u pull it and get 2.

And another good tip .. if replacing all 8 ... keep the 6 good ones as spares to test out when it happens again or to get you home or buy some tume. I keep at least 2 in the truck just in case

Ulonggapo said:

What are the cons of driving around with a misfiring engine?

Click to expand...

My wife drove around with misfires on her 03 for a couple of months. It trashed the catalytic converters from dumping too much unburned fuel into them. It ended up being a $1000 exhaust upgrade on top of other expenses fixing the misfires.

#1 and #5 coils, plugs, or injectors

Look for shit in the plug wells, that'll do it... 1 and 5 are the front pair, did someone spill liquids on the engine?

Get the plugs tightened if there is a tick. Top up the oil.