Hiya all.

We've been fighting and fixing a lot of issues we've been discovering with this 2005 Dakota SLT with the 4.7 4wd. From leaking injectors to the last owner using the cheap eBay knock off O2 sensors. All the O2 sensors have been now changed out for Denso branded OEM. Fuel injectors replaced (P&P yard to the rescue. No weepy injectors, good spray pattern and injectors have resistances of 13.3 to 11.8ohms) We've also played "Swap the coils" as well....

Here's what we have. We've been chasing down an issue that happens at times on a cold start- And more noticeable on a warm restart. The engine will shake and shudder, CEL flashes for misfires, etc. And suddenly the engine will run fine and no issues. Lots of power and pep.

Now we've found and resolved the weeping injectors, O2 sensors, etc. Last time it did this I pulled out my HT200 scan tool and gave the misfire monitor a close look. All 4 cylinders on bank 1 had registered misfires during the event. The other 4 cylinders on bank 2 are all fine and happy.

We're not throwing codes for any opens or shorts for the coils or injectors. I would think a severe vacuum leak might be a potential cause- However that would have a bad effect on the entire engine, and not just 1 bank.

So, riddle me this... What could cause 1 bank of the entire engine to start misfiring? And one bank only. Once it settles down the ol' girl runs pretty well. (Except that cheap O2 sensor caused the bank 2 converter to fail. P0430 code was thrown.) Other than that, P0430 code, just getting codes for random misfires and it did state Misfire #3. My scan tool revealed the misfires were occurring on cylinder 1,3.5, and 7.

There in is our problem. Wondering about the solution.

S-

 

Restriction on fuel rail crossover tube causing low start pressure on bank 1? Weak fuel pump prime?

​​​​​​​If you cycle the key on/off a couple of times before starting to prime the pump a few more times does it still misfire?

 

Oddly enough the fuel intake to the rail is at Bank 1....However there might be something fuel related going on here.

Fuel pump primes to about 55-60 PSI with a single key cycle. When it's running fine the fuel pressure hangs at about 55PSI. Now I'm using a Harbor Freight fuel pressure gauge, so that might be more like 50ish.

Here's the rub: When the engine is having the misfire episode the fuel pressure will rapidly fluctuate from between about 45 to 55. When it's idling decent the pressure sorta hovers at around 55psi. (very minor twitching)

This was before I changed out the fuel injectors with known 'good' injectors. (no weeping and had a decent flow and spray pattern) Also I blew out the injector rails 100% in case of any rust or debris. Problem came back. I have not repeated the pressure test with the replacement injectors however. But I suspect it's doing the same.

Not really leaning towards a fuel pump at this time, the pump is fairly quiet and the ol' girl runs fantastic once it settles down. Maybe something electrical is causing that one banks injectors to not operate correctly? I did pull all the spark plugs to inspect. Each plug looked fine, but did have some light tan deposits. (All plugs looked identical. Didn't see enough deposits on the plugs to worry about.)

I know it's something simple and stupid I'm just not seeing. One site mentioned that a plugged converter on that bank would cause a bank wide misfire event. I'd agree with that if we had drive ability issues. I know the Y pipe and converters will have to be changed out once we can afford it. (the one on bank 2 is tripping a P0430 code-) Bank 1 seems to be fully functional according to the scan data..

S-