Misfire on #3 that two shops can't figure out

[JimG2433]

I have an issue that the Dodge dealer can't figure out nor an independent shop.
This is on a 2014 Ram 1500 Laramie with the 5.7L, 200,000 miles.
Dealer: swaps plugs, coils, and injectors..... misfire did not follow. Tore down to valve covers to inspect valve springs, cams, rocker arms, lifters, etc.. and all checked within spec. Performed compression test and passed. Determined failure is more internal and recommended engine replacement.
Independent shop couldn't figure it out either, but did install new plugs and injector, with no change.
The engine does not seem to physically have a noticeable miss or run rough, however fuel milage seems lower.
Any ideas?

 

[Burla]

Just the general mis fire or specific? No other codes? Fuel PSI at rear of engine? What did they say could be internally bearing? Did you get an oil analysis?

 

[Ken226]

I have an issue that the Dodge dealer can't figure out nor an independent shop.
This is on a 2014 Ram 1500 Laramie with the 5.7L, 200,000 miles.
Dealer: swaps plugs, coils, and injectors..... misfire did not follow. Tore down to valve covers to inspect valve springs, cams, rocker arms, lifters, etc.. and all checked within spec. Performed compression test and passed. Determined failure is more internal and recommended engine replacement.
Independent shop couldn't figure it out either, but did install new plugs and injector, with no change.
The engine does not seem to physically have a noticeable miss or run rough, however fuel milage seems lower.
Any ideas?

They did something incorrectly.

A compression test isn't pass/fail. It returns a specific numerical value, which can be bad, good or anywhere in between. A bad cam cam can show pretty good compression at low rpm, but the engine still misfire at higher rpm due to valves only partially opening. A partially open valve let's in enough air @ 300rpm while cranking, but definitely does NOT at 3000 rpm.

If the compression is "within spec" but a couple dozen psi lower than all the other cylinders, through sheer dumb luck happens to be on the same cylinder that's misfiring, well, that's a clue So, pass/fail doesn't work.

What does "pass" = in pounds per square inch?



Also, all rockers were "within spec", needs to have a meaning attached. When it comes too a worn cam, it's the rockers range of motion that we are concerned with. A cam that has .005" worn off of the lobe will open the valve .005" less. The rocker will push the valve down less than normal, by an amount = to the thickness of a sheet of printer paper. They aren't likely to spot that with the naked eye.

I like to measure with a long reach dial indicator on a mag base, while a helper turns the crank bolt.



There is no magic scenario where everything is fine, but it still misfires. There is a competency crisis in America these days as boomers retire and GenZ trades in their purple hair dye and puberty blockers for full time jobs.
It's unfortunate, but competent shops seem to be very, very few and far between.

This, is an excellent post on the same subject:
Post in thread 'P303 good coil pack, good plugs, new injector, and good compression' https://www.ramforum.com/threads/p3...ctor-and-good-compression.222680/post-3070633

 

[GeauxinUp]

Leak down test?

 

[Ken226]

Leak down test?

Yup. Should have been done if the compression on 3 had been lower than the rest. While listening with a stethoscope in the intake and exhaust to identify which valve, or if the rings.

 

[JimG2433]

It started with just the P0303 code. Checked the codes today and it's got a few more now..... P0303, P0300, P0440, P0456.
Forgot to mention the evap code came up before taking to the second shop and did a smoke test and found nothing. The P0300 is new.
I'm taking it to an "old school" shop tomorrow, so will see what they say.
Was hoping someone would point me to something stupid easy, but it's looking like it's going to be more serious.

 

[EdGs]

200k is a good bit of mileage.

Any "tick"?

If the misfire did not follow the injector/plug/coil swap, and they did not find a broken valve spring, you might just be the next winner of the cam and lifter lottery.

My '15 made it to 201k, when I won that lottery last year.

They should have pulled the VVT solenoid and checked for metal on the screens, or cut your oil filter open and check for metal glitter there.

Wish you the best for a solid fix, please keep us posted.

 

[EdGs]

@Ken226, do you happen to know how much a cam lobe needs to be worn down to cause a misfire?

I was not yet to the point of a misfire on my Ram, but my cam was chewed up pretty good (.030 or more). I will have to measure the worn lobe and see just how much smaller it is that the others.

 

[Ken226]

@Ken226, do you happen to know how much a cam lobe needs to be worn down to cause a misfire?

I was not yet to the point of a misfire on my Ram, but my cam was chewed up pretty good (.030 or more). I will have to measure the worn lobe and see just how much smaller it is that the others.

No, as it's different depending on the combination of the amount of lobe wear, manifold pressure and the rpm.

Consider: the piston speed is determined by the crankshaft angular velocity (rpm), so, at low rpm the piston is descending relatively slow on the intake stroke, and enough fuel/air can flow in, even through a partially open valve. Especially if the manifold pressure is high due to the low rpm, open throttle blade combination.

But consider the opposite. At higher rpm, in conjunction with a lower manifold pressure and a worn cam lobe, partly open valve, the fast descending piston can't get enough air into the cylinder. But the PCM doesn't know that, so the injector sprays the normal fuel charge and results in a super rich mixture, and it misfires.


So, how much wear would cause this would be pretty complex and depend on throttle blade position, rpm, engine load, air pressure, and probably other things I haven't even thought of. And change, as those conditions all change.

 

[EdGs]

No, as it's different depending on the combination of the amount of lobe wear, manifold pressure and the rpm.

Consider: the piston speed is determined by the crankshaft angular velocity (rpm), so, at low rpm the piston is descending relatively slow on the intake stroke, and enough fuel/air can flow in, even through a partially open valve. Especially if the manifold pressure is high due to the low rpm, open throttle blade combination.

But consider the opposite. At higher rpm, in conjunction with a lower manifold pressure and a worn cam lobe, partly open valve, the fast descending piston can't get enough air into the cylinder. But the PCM doesn't know that, so the injector sprays the normal fuel charge and results in a super rich mixture, and it misfires.


So, how much wear would cause this would be pretty complex and depend on throttle blade position, rpm, engine load, air pressure, and probably other things I haven't even thought of. And change, as those conditions all change.

Interesting.

Now, I don't haul ass everywhere, but I do (and did) exercise the skinny pedal a little. Guess I'm trying to hang on to my youth....lol.

I'm gonna measure those cam lobes just out of curiosity. I'll bet I wasn't too far from a misfire.

 

[Daniel from Texas]

I have an issue that the Dodge dealer can't figure out nor an independent shop.
This is on a 2014 Ram 1500 Laramie with the 5.7L, 200,000 miles.
Dealer: swaps plugs, coils, and injectors..... misfire did not follow. Tore down to valve covers to inspect valve springs, cams, rocker arms, lifters, etc.. and all checked within spec. Performed compression test and passed. Determined failure is more internal and recommended engine replacement.
Independent shop couldn't figure it out either, but did install new plugs and injector, with no change.
The engine does not seem to physically have a noticeable miss or run rough, however fuel milage seems lower.
Any ideas?

It sounds like you are losing the Cam.

 

[farmboy561]

I went through exactly what your going through with my 2015 longhorn hemi. Almost all 2006+ Ram 1500s with the 5.7L Hemi V8 and automatic transmission have MDS. Drove us crazy to try and find the problem. Tried everything I was reading on here.

Cam lobes were worn. Got the MDS delete kit and installed it from diablo. Got both heads done while off since they had to come off anyway.
Hemi tick gone now. True Hemi now with V-8 all the time. No more of that 4 cylinder crap with issues.
Added cold air intake filter from "Rough Country" as well. Now it had more intake air flow than was allowing it to exhaust. Changed the exhaust to Borla, (there are others will work as well) to let the Hemi loose so the exhaust flow would match the intake air flow. It's a true beast now! Silent with no more ticking. Such great acceleration and kick down now.

Deleting the Multi-Displacement System (MDS) on a Ram 1500 5.7L Hemi involves physically removing components like lifters, solenoids, and the camshaft for permanent removal. This fixes potential lifter tick/failure issues and provides8-cylinder power consistently.

 

[Dusty]

To troubleshoot a misfire, instead of a compression test I would suggest doing a power balance test with a scanner first, then a leak down. I don't think losing even .010 off the lobe is going to cause a misfire. I've seen cams come out of engines with more wear than that and not misfiring.

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 147030 miles.

 

[Clatech]

Mine did that, did all the changes you mentioned as well. After great expense and much time it ended up being the ECM. It would quit advancing the timing and misfiring the number 3 cylinder on my 5.7. I noticed the mileage getting worse and also the the coolant temp fluctuating a lot when going up and down inclines. Also lose of power when climbing grades. Also on mine when this started happing I noticed after a while it was charging almost 16 volts. The ECM went crazy...... Good luck!

 

[N0NAMETOGIVE]

I had these rotating codes so I tightened everything that I could, and cleaned all of the electrical plugs to make it go away. Sometimes a weak battery will create issues.

 

[N0NAMETOGIVE]

I also had p0300 p0301 and p0308.

 

[atlgator]

Don’t forget the high volume oil pump. Winner of the camshaft and lottery 2 years ago on my 2011 5.7 at 170k
Programmed the computer off mds. Bought the non mds lifters and camshaft but waiting for the remanufactured warranty of 3yrs or 100k miles to end before that happens. The high volume oil pump is a must also. 8 months without the truck was rough. 5w30 also with lubegard each oil change. Lesson learned

 

[dodge daddy]

I have an issue that the Dodge dealer can't figure out nor an independent shop.
This is on a 2014 Ram 1500 Laramie with the 5.7L, 200,000 miles.
Dealer: swaps plugs, coils, and injectors..... misfire did not follow. Tore down to valve covers to inspect valve springs, cams, rocker arms, lifters, etc.. and all checked within spec. Performed compression test and passed. Determined failure is more internal and recommended engine replacement.
Independent shop couldn't figure it out either, but did install new plugs and injector, with no change.
The engine does not seem to physically have a noticeable miss or run rough, however fuel milage seems lower.
Any ideas?

they did a compression test, it was good, and they want to replace motor? DONT EVER GO THERE AGAIN. check wiring harness and ECM

 

[robram19]

I had this problem on a 2.4 turbo P T Cruiser and it turned out to be a leaking intake manifold gasket found by passing an unlit propane/butane torch around the gasket area while idling. Give it a try and good luck!

 

[EdGs]

To troubleshoot a misfire, instead of a compression test I would suggest doing a power balance test with a scanner first, then a leak down. I don't think losing even .010 off the lobe is going to cause a misfire. I've seen cams come out of engines with more wear than that and not misfiring.

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 147030 miles.

This was not enough to cause a misfire, but I'll bet it wouldn't have been too much longer before a misfire popped up.