DocRoche

Hey guys, got an issue. I was idling real rough and truck was stalling. Got codes P0171 and P0174. Cleaned the MAF, replaced fuel filter, cleaned throttle body, replaced pcv hose. Today I replaced the intake gaskets. While i was doing that I replaced the spark plugs with Motorcraft spark plugs. Took it for a test drive, ran great with no idling issues or stalling.

Took it on one more drive before going to bed and engine light started blinking, truck ran rough. Light came on and stayed on. Got the code P0304 cylinder 4 misfire. Got a brand new plug in it. Should i replace the cop? Im stumped. My old issue is gone with a new one replacing it. Any ideas?

mbb

If you have a PCV manifold leak this is the cylinder closest to where that comes in that and might run lean due to getting most of the fresh air . Check your PCV hose you might have damaged it could be in bad condition and you moved it just enough to make it happen.

Swap the coil with another from a cylinder that does not have the misfire and see if the misfire moves first.

If the misfire is still on cylinder 4 then swap the injector with another cylinder and see if the problem is still the same.

Jbrew

You may have to drive it for a little while after swapping coils for the misfire to reappear. The PCM will force fire a bad coil if it's a low grade misfire. After a short amount of time it will eventually miss again, but yea, the miss should move to which ever cylinder you swapped to.

DocRoche

Thanks, I'll try that in the morning. I'd hate to think it's a leak after replacing the intake gaskets. 1st test run was great, plus we put in all new plugs. I'll recheck the hoses and swap the coils, see if I can narrow it down. Hopefully nothing serious. Just can't think of what it could be if it's not the cop.

mbb

Bad spark plug
Fouled plug/bad gap
Bad injector
Bad cop
PCV leak
Manifold air leak
Manifold coolant leak
Bad injector wire / plug
Bad cop wire/plug
Bad pcm ground
Bad pcm
Bad head gasket
Cracked head
Burnt/damaged Valve
Burned piston/ hole
Bad rings/ compression

Etc

R&TBabich

It may not be the entire COP.
The boot may be degraded.
The coils last a lot longer that the boots.
I've had good service with Denso 671-0001 boots.
How many miles on the COPs?

Jbrew

Well, your on the right track. An intake gasket job isn't that tough to accomplish correctly. You just have to be very thorough on the prep work. Like say, hit the heads with a palm sander, then wipe them clean with lacquer thinner. That's the quickest and best way since even as much as a finger print can cause them to fail. Then there's the tie down. The manual has it in two stages. 3 or 4 stages is even better to bring it down as even as possible. But yes, many fail due to a reckless or impatient install practice. So again, not difficult, but critical lol.

DocRoche

145,000. I will say they looked terrible when I pulled them off.

DocRoche

Thats a lengthy list but thank you. If it was a coolant leak wouldn't i see antifreeze? Just curious. I'll check the list starting with swapping coils. Thank you very much.

DocRoche

I really hope its not with the gaskets cause we got those as smooth as I thought they could be. But thats a possibility. Thank you!