Hey guys, I have a problem,
2004 Dakota 4.7l 4WD. 190,000 miles. I recently had driver side exhaust manifold gasket #7 cylinder back two bolt heads popped off and blew the gasket out. Believe it or not I had zero problems replacing it, all bolts came out with no issues!!

But when I started it up, it ran very rough. It has a lot of back pressure at the tail pipe. Codes read multi cylinder misfire. I pulled all the spark plugs, they all looked clean and dry, gaps were correct. I have a strong smell of unburnt fuel (makes me assume injectors are good). With the engine running, I pulled each coil pack one at a time and it made no difference in the rough idle. The CEL blinks but does not stay on. Once I accelerate to 55-60 (18-1900 rpm)it smooths out.
I will be doing a compression test on the cylinders as soon as I get a tester.

Any suggestions?

 

Wild guess..... I had similar issue, it was resolved with a new cap and rotor. Inside the cap was arced, and the rotor got so hot it burned thru...
Just like you, it was fine , until it wasn't!

 

This is a 2004… it has coil packs, as I stated, it does not have a “rotor cap”

 

Last time I had a misfire, it was due to a seized hydraulic lifter, which caused rocker ejection on #5 cylinder intake valve. If you're getting misfires all over the place, it might be the crank sensor, which you want to go with Mopar if you replace.

https://dodgeforum.com/forum/2nd-gen...e-issue-2.html

https://dodgeforum.com/forum/2nd-gen...-not-soak.html

 

This sounds like low compression. I wonder if you have been low on compression for a while and then had a no ignition situation that made it fill the exhaust with fuel. Could explain the broken bolts. Don't run the truck till you can do a compression test. You'll just fuel wash the cylinders and make it worse.

 

Interesting thought, but I had an exhaust leak for a while (about 2 months) and the bolts were pretty rusty. I will heed your advice.
The only code I’m getting is P-0300 multi cylinder misfire.

 

Unclear of you statement but if you refer to "backpressure at tailpipe" as putting your hand over the pipe to measure the flow, that's accurate.

I agree with the others, this sounds likely mechanical or a sensor issue. Odd that you only have P0300; It should be accompanied by 0301-0308 signifying any 2 or more cylinders.