Misfire in Dodge 4.7 - out of my comfort zone 2001 Dodge Dakota

Hey Guys,

I'm at my wits end with my brother's truck. We're getting a misfire on cylinder 2.

Spark plugs, coils, rockers and lifters, injectors, PCV valves ( they were broken), and fuel pressure checked.

They were all due, so not a big deal - but what's left?

Wiring and ECU? Checking compression on that cylinder? Does anyone know if those are common failure points on that engine body?

Is there an easy way to check if a coil is getting a signal? 

All other spark plugs looked good, but number 2 looked like this (on the right):



Any help is appreciated!

A compression check is long overdue.  A leakdown test would be even better.

In reply to APEowner :

Roger. Hope to do it today.

The black on the plug indicates too much fuel.   Usually

Fuel injector is stuck open.

That plug is/was firing some of the time to get that color and it shows heat down the threads.

Replace the #2 plug, if that doesn't change anything the plug was good

Swap coils with another cylinder, if the problem does not change cylinders the coils are good.

then swap injectors with another cylinder, Check the inlet screen on the injectors for cooties.

Try a can of CRC intake valve cleaner? NOT SEAFOAM!

Ranger50 said:

Fuel injector is stuck open.

Or low compression causing a rich condition.

Find a Noid light kit.  The ECU grounds the injectors to fire them (I think), so if you have a broken wire on the way to the ECU and it's touching a ground, it might be holding the injector open.  You can also test that by removing the injector, pulling the fuel pump fuse, and seeing if it opens when you turn on the key.

Intake manifold leaks were somewhat common which could explain the misfire, but wouldn't explain the black plug on the offending cylinder.

Testing coils sometimes reveals that they're OK, but they malfunction under high voltage conditions.  Try swapping coils and see if the misfire moves or stays on #2.

Burnt valve.

Coils have been swapped around AND replaced.
Plugs have been replaced.
Injectors have been replaced. 
Rocker arm and lifter have been replaced.
Fuel pressure confirmed good.

Where can I get a "noid light" ? Is that something to rent or ???

Sounds like I need to check the compression first, and make sure the injector isn't grounded open.

Thanks guys! You give me hope I can fix this. (my family thinks I can fix anything, jokes on them)

 

Compression test. 

I have an '06 w/185k miles running on 6-1/2 cylinders.  6 were at 150psi, #2 is 110psi and #7 is 80psi.  I know it's the exhaust valves because the Jet-Hot coating is getting burnt off my Doug Thorley headers on those two cylinders.  They used powdered metal valve seats and your lucky if they're just burnt, vs falling out and breaking into pieces.  I'll be tearing mine down this weekend.

In reply to accordionfolder :

"You give me hope I can fix this. (my family thinks I can fix anything, jokes on them")

Hey, fake it 'till you make it. We've all been there!

Dodge engine ending in .7 means it's just time to throw it away and start over. I wish I was kidding.

Compression test. Leakdown would be better but you can also make a compression tester into a leakdown tester if you take out the schrader valve and know how to find TDC of compression stroke on that cyl.  

Considering the reputation for dropped valve seats, replacing the rocker/lifter would have been an opportunity to spin the engine around until each valve of that cyl was completely closed to make sure they raised up as far as the rest of the valves. A dislodged valve seat would make a valve stay slightly lower than all the other valves (in their respective closed positions).  But a leakdown test will diagnose for this anyway. Just throwing that out there in case you're ever in the same situation again. 

Not uncommon for valves to stick open on the 3.7 and 4.7.

Also check for broken valvesprings.

Hey guys, compression check done (finally). We're seeing roughly 120 all around, nothing standing out. Time to swap the ecu and harness?

Hemi swap. 

I sent my heads to Southeast Cylinder Head in Orlando.  They cut out the powdered metal valve seats and installed conventional hardened valve seats.  They refurbished the heads for a reasonable price and my '06 is running like new again. I made a tool for checking ring leakdown with the heads off just to make sure my rings were still in good condition while I was waiting for the heads to come back.  I'll be glad to lend it out for the cost of postage.  

Have you done a leak down test?