I have been occasionally having an issue when starting the truck while the engine is warm. One or more of cylinders will misfire and the check engine light will come up. After driving a little down the road the misfire goes away and the engine runs fine again. So far it seems to only happen after starting the engine, and it doesn't happen every time. Sometimes it's cylinder 1, 2, 8, or a combination of those. It only started getting bad once the temperature got up in the spring time here in Wisconsin.

I am curious, could it be bad injectors? But what are the odds that the injectors would fail at the same time, and only have a problem when the engine is starting up after it has been shut down for about ten to fifteen minutes? Even then, it's random.

Truck: 2000 Dodge Dakota, 4.7L V8 Automatic, Quad Cab

 

I forgot to mention the check engine codes that can come up when this misfire happens. They can be P0201, P0202, P0208, or P0308. The truck has a bit over 219k miles on it.

Anyone have any ideas?

 

I think it unlikely that you have so many injectors failing at once. Have you checked the connectors, all clean and tight?

P201, Injector #1 control circuit
P202, Injector #2 control circuit
P208, Injector #8 control circuit
P308, Cylinder #8 misfire

I haven't had this happen yet, but I've heard that sometimes this can happen when the TPS goes bad. It's a quick and easy replacement. It sort of makes sense since the injectors responds to the TPS.

I hate to just change parts but failing that I think you'd be looking into the PCM being a problem.

On #8, when's the last time you checked the plug?

 

I checked the spark plugs for cylinder 1 and 8 tonight and they appear to be in good condition. The spark plug for cylinder 2 is buried under stuff, but I suspect that one is also in good condition.

I took a close look at the wires leading to the ignition coils and they look old, but normal. I looked at the connectors themselves and they also look old, but normal. The ignition coils do look a little old as well. It is possible that occasionally one or more of them could be failing when they're hot. It could be worth replacing the ignition coils.

As I was pulling the ignition coil out for cylinder 8 to get at the spark plug, a little rubber o-ring came apart since it was split in half. I put electrical tape on it to hold it together until I get to the auto parts store tomorrow to get a new one.

I'll take a look at the throttle position sensor tomorrow as it's late in the day and dark out. If the throttle position sensor was malfunctioning, wouldn't it cause all cylinders to have an issue?

 

The TPS position affects the fuel injector pulse width. Is it a possibility, yes, but I agree as to why it wouldn't be all cylinders. Still, it's an easy swap. Could you have multiple injectors failing? Sure.

Can you check the fuel pressure?

The injectors share a common feed from the ASD relay, the PCM switches the grounds.

 

The bad rubber insulator on the ignition coil that covers the top of the spark plug could not be replaced on its own, so I replaced the ignition coil. The guy at the auto parts store said that it may have been the cause of the misfire on cylinder eight. I'll have to see if it helps. It hasn't misfired since the replacement in the past couple days.

 

Although the misfire on cylinder 8 is fixed, I'm still getting a rare P 0202 on cylinder 2, and I can feel the misfire when the code comes up. I decided to check the resistance of this injector and got 15.7Ω. The service manual says the resistance of the injector should be 12Ω + or - 1.2Ω. Should I replace this injector, or is 15.7Ω close enough? About 30.8% is a lot more than the tolerance of 10%, though.

 

I'd call that slightly high...what is it on the others?

high resistance means more heat and less current = less force = less fuel (can't open plunger fully)

 

Cylinder 8 injector is at 17.5Ω, cylinder 6 injector is at 14Ω, and cylinder 1 injector is at 19.2Ω. The others aren't as "easy" to get to without removing the fuel rails and other various tubes and pipes, but I have a feeling they're all out of spec. They all look pretty old and may all be stock. My multimeter could be off since it's a cheap Walmart one, but I doubt it's that far off. When crossing the leads it shows a resistance of 0.2Ω which is probably the resistance of the lead wires.

 

I replaced the fuel injectors. The truck runs much smoother and there are no more misfire/injector circuit issues. The new ones are within spec.