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Amedee
Amedee, Dodge Technician
Category: Dodge
Satisfied Customers: 24766
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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05 Ram 1500 5.7L Has random multiple misfire code. I

Customer Question

05 Ram 1500 5.7L Has random multiple misfire code. I replaced the spark plugs, spark plug wires & air filter and reset the computer. 5 miles down the road the MIL light came back on with the same code P0300. I've double checked to make sure I didn't leave anything disconnected. It goes down the road great, but it stumbles for a few seconds accelerating from a dead stop. Then it smooths out and really takes off. What am I missing??
Submitted: 3 months ago.
Category: Dodge
Expert:  Amedee replied 3 months ago.

Hello and welcome!

My name isCustomerand I can assist you with your question.

Expert:  Amedee replied 3 months ago.

Can I start by getting your VIN?

Thank you!

Customer: replied 3 months ago.

1D7HU18D35S201915

Expert:  Amedee replied 3 months ago.

Thank you for the VIN!

The most common cause for this condition and code you are experiencing are the following..

Oxygen sensor

Carbon valves

Sticking valves

Broken valve springs

leaking or plugged fuel injectors

Expert:  Amedee replied 3 months ago.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

Please let me know if you have any further questions.

Customer: replied 3 months ago.

Well, that's not very much help. How am I supposed to determine which on your laundry list is the culprit?

Expert:  Amedee replied 3 months ago.

I can provide you with some tests that will help.

Expert:  Amedee replied 3 months ago.

For example, you can check engine vacuum to see if there is a valve train issue

Expert:  Amedee replied 3 months ago.

If the fuel injectors are leaking, it will show up on a leak down test.

Expert:  Amedee replied 3 months ago.

And you can watch the oxygen sensors signals while this occurs to see if they are acting up. You can do this with a voltmeter or a scanner if you have access to one that can read live data.

Expert:  Amedee replied 3 months ago.

I hope that helps clear things up. Please let me know if you have any further questions.

Customer: replied 3 months ago.

We've worked together before and you were much more direct and to the point. Why are you suddenly speaking in generalities and not forthcoming?

The truck idles smooth and cruises smoothly. It stumbles accelerating from a stop. Before replacing the plugs & wires it pretty much ran like crap all the time. If it were in your service bay, rather than saying maybe it's this or maybe it's that...what would you test and/or check first and how do I test and/or check it? I have an aftermarket scanner and a DVOM. Beyond that it's just me and my hand tools. I don't have a lab scope or anything, so I can't be looking at waveforms and such.

Expert:  Amedee replied 3 months ago.

I would start by checking the basics. This means at least ruling out a base engine mechanical problem. You would do this by using a hand held vacuum gauge to ensure that it is not fluctuating at idle. I did not go into detail about this because I assume you know how to use a vacuum gauge and what readings to look for. If not, I can go into further detail.

In addition, valve springs and leaking valves are VERY common on this vehicle. If this turns out to be it, the cylinder heads must be removed and sent out for repair.

You can also run the engine on alternative fuel to see if the engine runs any better. If so, then you know it is a fuel delivery issue. Again, I assume you knew this.. sorry about that.

Expert:  Amedee replied 3 months ago.

In addition, you did not ask how to diagnose the problem in your first post. If you would have, I would have provided more information about diagnosing this issue in my first answer. I will be happy to help in anyway possible, but please be clear on your questions and if you want diagnostic steps, please mention that in your initial post so I know what your expectations are up front.

Customer: replied 3 months ago.

Well using a vacuum gauge I've got 18 in Hg at idle. The O2 sensors seem pretty normal and equal. But the fuel trim looks messed up to me.

Short term fuel trim bank 1: -3.3%, bank 2: 11.7%, bank 3: 60.2%, bank 4: 43.0%. Long term fuel trim bank 1: -3.1%, bank 2: -3.1%, bank 3: 60.2%, bank 4 -73.4%. What does that say to you?

Expert:  Amedee replied 3 months ago.

Fuel control is a bit out of whack. However, wont be able to pinpoint the root cause just by the fuel trim numbers.

Expert:  Amedee replied 3 months ago.

Have you checked the fuel pressure under a load when this issue occurs?

Customer: replied 3 months ago.

I see. The vacuum gauge wasn't fluttering or anything, so I'm thinking I don't have leaking valves anyway. I guess I'll clean the fuel injectors and see what that buys me.

Expert:  Amedee replied 3 months ago.

Keep in mind, even if the valves are not sticking at this point when you checked engine vacuum does not mean it is not an issue when driving. They stick intermittantly. The reason I say this is because it is VERY common on this engine.

Expert:  Amedee replied 3 months ago.

In addition, I dont think cleaning the injectors will help. If anything, they will need to be replaced.

Expert:  Amedee replied 3 months ago.

I would check the misfire counts on your scanner to see which cylinders are misfiring.