Random misfire after new engine install

[Dcwhite]

I have a 2011 Ram with 5.7. I have had two engines put in my truck due to cam lobe failure. The most recent engine I just had put in has twice already thrown random multiple misfire code. I had new plugs and coil packs installed. The code pops up randomly and it’s only at idle. What would be the cause of the random misfire code?

 

[rzr6-4]

Does it run poorly? Or runs good and it's just something that the sensor is able to detect?

I know you said just at idle but is it all the time or just in certain conditions? Mine has a history of running poorly, but the only time I've gotten the multiple misfire code was when it was REALLY cold, and I was trying to accelerate into a headwind. It sounded terrible when it did it.

 

[Dcwhite]

It runs great. Just randomly pops up. It popped up today by just starting my truck and idled for like 3 minutes

 

[mtofell]

The code only at idle is curious... I had it come up in my 6.4 Hemi but was only under hard acceleration. Are the codes on the same cylinder(s)??

 

[metalchewy]

Wondering, Did they install the grounding straps?

 

[Dcwhite]

That’s the thing it’s not on a certain cylinder. Code says multiple/random cylinder misfire. When it did it on the previous engine, code was the same but on cylinder 8 after 27k miles. I thought it was the coil pack, so I changed it. Didn’t fix it. Turned out #8 cam lobes flattened. Warrantied out that engine for the one I have now and I’m getting random cylinder misfire code after about 1500 miles

 

[Dcwhite]

Wondering, Did they install the grounding straps?

Yes they did

 

[Burla]

keep running codes like every time you start it or end a drive, can you post the codes, so no other codes showed up? exact code p0300? timing or camshaft position sensor are usually suspects. Most of us assume everything was done right as far as fuel delivery and vacuum. One would have to ask, why replace plugs and packs on a new engine? The way you wrote it or the way I read it was that you had codes after a new engine, then you installed plugs. Is that just mis order, did you mean to say the new engine had new plugs and packs?

 

[Dcwhite]

keep running codes like every time you start it or end a drive, can you post the codes, so no other codes showed up? exact code p0300? timing or camshaft position sensor are usually suspects. Most of us assume everything was done right as far as fuel delivery and vacuum. One would have to ask, why replace plugs and packs on a new engine? The way you wrote it or the way I read it was that you had codes after a new engine, then you installed plugs. Is that just mis order, did you mean to say the new engine had new plugs and packs?

From the factory engine it had 160,*** miles on it when the #2 cam lobes went flat. I didn’t change plugs on that engine. Dealership put old plugs in second engine. I replaced plugs and coil packs on second engine. Everything was swapped over to current engine.

 

[rzr6-4]

Dealership put old plugs in second engine.

Holy crap, how cheap can they be? Probly due to be replaced anyway, then going through the extra effort to move them over. Sounds like a dealer I would want nothing to do with.

To your issue, I would think weak battery, bad grounds, or low fuel pressure. There are a lot of things that *might* cause it, so it can be hard to find the one that IS.

 

[Dcwhite]

Holy crap, how cheap can they be? Probly due to be replaced anyway, then going through the extra effort to move them over. Sounds like a dealer I would want nothing to do with.

To your issue, I would think weak battery, bad grounds, or low fuel pressure. There are a lot of things that *might* cause it, so it can be hard to find the one that IS.

Battery is just over a year old. Last two times, hence new engines, the misfire code pops up has lead to cam shaft failure.

 

[Hootbro]

First thing I would do is have a scan tool that can track each cylinder misfire count and look for a pattern. While individual cylinder misfire counts may not be enough to set a code for a individual cylinder, there still may be enough between the cylinders to trip the random code.

Could also be a crap intake manifold install, especially if they reused the old gaskets.

 

[Dusty]

When troubleshooting random misfires (P0300), it is important to investigate all accompanying codes. This usually points to the source or area of the problem.

ie: low fuel pressure, EVAP, timing, emissions codes, etc.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 123497 miles.

 

[Dcwhite]

First thing I would do is have a scan tool that can track each cylinder misfire count and look for a pattern. While individual cylinder misfire counts may not be enough to set a code for a individual cylinder, there still may be enough between the cylinders to trip the random code.

Could also be a crap intake manifold install, especially if they reused the old gaskets.

MIL hasn’t popped up in a couple weeks. Next time it does I’ll dbl check all codes.

 

[Dodge 1500 4X4]

Was the intake plenum replaced after the chewed cam lobe roller lifter metal filings being circulated into the lubrication system, allot of that metal Debree would collect in the intake plenum and cannot be cleaned, was the VVT solenoid checked for metal Depree and replaced.

 

[Marshall]

Any shop that would reuse 160k plugs in a new motor likely used old gaskets
Are these reman motors or did that same shop rebuild them?

 

[Mark Harrison]

need to find someone with a eight channel oscillosope and monitor plugs/coils/ wires and supply voltage

 

[GTyankee]

p0300 only means that something is wrong at one of the cylinders
It is a Generic Code, in other words nothing specific is wrong

It may just clear itself, just keep an eye on the EVIC

 

[Burla]

Any shop that would reuse 160k plugs in a new motor likely used old gaskets
Are these reman motors or did that same shop rebuild them?

I had warranty work on a transmission done once, they reused the main seal, and it leaked til the day I sold it. They wouldnt fix it, said "in tolerance". So this statement is absolutely true. My guess is on warranty work they would say we don't owe you new items, just fix it that most suits us. However, my guess is any shop that would do this on warranty work would probably do it when you have to pay as well. When you see a shop with any bad habits, find a new one?

 

[N0NAMETOGIVE]

The code only at idle is curious... I had it come up in my 6.4 Hemi but was only under hard acceleration. Are the codes on the same cylinder(s)??

PCV Valve resolved mine when plugs didn't.