Rough Idle, Misfires, Rough acceleration, any help?

[Hemi395]

I'll take it to AutoZone and see if there's a vacuum leak then. I'll also check the Map sensor. I got a superchips tuner, will that be able to see the map sensor live data? I'll find out here in about 30 minutes.

Not sure about Superchips, but on my Diablosport Trinity I can monitor the MAP sensor. It should be pulling about 20 hg at idle and close to 0 on acceleration....

 

[joshuaeb09]

Those map sensors can also go bad, don't cost much, and are super easy to replace. I finally convinced my old man to pick one up for his and installed it in like 60 seconds. Truck runs better, he says it tows better, and he's getting slightly better MPG.

 

[Hemi395]

Those map sensors can also go bad, don't cost much, and are super easy to replace. I finally convinced my old man to pick one up for his and installed it in like 60 seconds. Truck runs better, he says it tows better, and he's getting slightly better MPG.

Where is that on the intake manifold, in the back by the pcv valve?

 

[joshuaeb09]

Where is that on the intake manifold, in the back by the pcv valve?

Yup right there on the back passenger side. Just unplug, twist out, twist the new one in, and replug. Since his truck went 80+k before he put a CC on it it was a bit oily. Probably could've cleaned it up, but I think the replacement was like $22 and the truck was over 100K so no brainier to replace it.

 

[Cowboy Brick]

Not sure about Superchips, but on my Diablosport Trinity I can monitor the MAP sensor. It should be pulling about 20 hg at idle and close to 0 on acceleration....

Checked the MAP Sensor. It was reading 4.5-8 at idle and going all the way up to 14 when giving it gas and accelerating.

 

[Hemi395]

Checked the MAP Sensor. It was reading 4.5-8 at idle and going all the way up to 14 when giving it gas and accelerating.

Is that voltage or hg?

 

[Cowboy Brick]

So after a while with the truck always misfiring I was sitting in the parking lot for 25 minutes with the truck in park,w and the truck was idling without misfiring! I thought God had come and blessed my truck and showed me it wasn't a mechanical issue.

So what can we narrow it down too? Air-fuel ratio?
I took a photo of my tuner with the Long Term Fuel Trim and Short Term Fuel Trim banks with the truck idling.

 

[joshuaeb09]

Odd that the banks are way off from each other. I don't wanna say cam/lifter issues, but it's quite possible knowing what we know about the Hemi. It could also be related to the O2 sensors or from the plugs that all got replaced. Did you do a PCM reset since things have been replaced to see if those fuel trims come closer together ? Without pulling the valve covers to see if any of the valves aren't fulling opening in relation to their neighbor's it's hard to speculate if it's related to the cam/lifters.

 

[Hemi395]

So after a while with the truck always misfiring I was sitting in the parking lot for 25 minutes with the truck in park,w and the truck was idling without misfiring! I thought God had come and blessed my truck and showed me it wasn't a mechanical issue.

So what can we narrow it down too? Air-fuel ratio?
I took a photo of my tuner with the Long Term Fuel Trim and Short Term Fuel Trim banks with the truck idling.

View attachment 172648

View attachment 172649

If I'm reading that right, it looks like Bank 1 is pulling a ton of fuel and Bank 2 is adding a ton of fuel. I would start looking at the O2 sensors and see if they're oscillating like they should be. It's almost as if one is stuck open which is causing one bank to lean out and the PCM is compensating with the other bank dumping fuel in...

 

[Fitz-0518]

^^^^Listen to this guy. Cowboy I hate to say this. I know you want to resolve the drive condition your self. I get that. But this is one of those engine conditions that can cost us a small fortune as we guess and throw parts at it.
This is where an investment in a qualified tech who has a professional scanner for $100-$200 is cheap diagnostic time. Now you know. What I see is we need to read the run condition against the factory specs. That requires a professional scan tool held and used by a tech who understands how to run the diagnostic steps that isolate the problem. Sure want to see you get your truck running right. Just sharing what my experience has taught me.

 

[joshuaeb09]

^^^^Listen to this guy. Cowboy I hate to say this. I know you want to resolve the drive condition your self. I get that. But this is one of those engine conditions that can cost us a small fortune as we guess and throw parts at it.
This is where an investment in a qualified tech who has a professional scanner for $100-$200 is cheap diagnostic time. Now you know. What I see is we need to read the run condition against the factory specs. That requires a professional scan tool held and used by a tech who understands how to run the diagnostic steps that isolate the problem. Sure want to see you get your truck running right. Just sharing what my experience has taught me.

In this case I'd want to see a plot of fuel trims, Pre Cat O2's, injector duty cycle, timing advance, ST KNK, and engine speed while doing a test drive. I'd also want to run a power balance test if possible. It could be cam/lifter, it could be the O2's, or hell with trims out of wack like that could be injector related. It's hard to tell without more data. If the super chips can do data logging a log might help assuming it will log all relevant pids. The datalogging with some of the tuners is limited so it might take a professional scan tool or like I used to use a laptop with a highspeed USB -> OBD2 interface that can keep up with polling that many pids concurrently and run more advanced tests.

The upside to someone with a professional scantool is the ability to run a power balance test along with some additional diagnostics that you're not going to get without spending some serious money on the tools yourself.

 

[Gone]

check the two plugs on ur pcm are they seated all the way on?

 

[Fitz-0518]

In this case I'd want to see a plot of fuel trims, Pre Cat O2's, injector duty cycle, timing advance, ST KNK, and engine speed while doing a test drive. I'd also want to run a power balance test if possible. It could be cam/lifter, it could be the O2's, or hell with trims out of wack like that could be injector related. It's hard to tell without more data. If the super chips can do data logging a log might help assuming it will log all relevant pids. The datalogging with some of the tuners is limited so it might take a professional scan tool or like I used to use a laptop with a highspeed USB -> OBD2 interface that can keep up with polling that many pids concurrently and run more advanced tests.

The upside to someone with a professional scantool is the ability to run a power balance test along with some additional diagnostics that you're not going to get without spending some serious money on the tools yourself.

That is exactly what I am referring to. Also, when Cowboy checked his radiator,,,,could it be a head gasket. Hope not

 

[Cowboy Brick]

I went to the dealership and they ran tests and stuff,
I was told C1, C3, and C7 are the misifiring cylinders and the mechanic thinks it's broken valve springs.
I was planning on removing the valve cover tomorrow morning and seeing it myself since dealership wanted $500 to do that themselves...

 

[Cowboy Brick]

check the two plugs on ur pcm are they seated all the way on?

They are seated all the way on

 

[Cowboy Brick]

Took the valve cover off, couldn't get it out of the engine bay but was able to check the valve springs and make sure it wasn't the springs like the dealership said. The springs look completely fine.

 

[Cowboy Brick]

Here's a video of it running with the valve cover off.

 

[joshuaeb09]

At your mileage it could possibly be the lifter/cam issue. This video outline's it pretty well as well as how you can diagnose it with the covers off.

 

[Cowboy Brick]

At your mileage it could possibly be the lifter/cam issue. This video outline's it pretty well as well as how you can diagnose it with the covers off.

Yeah I've seen that video, and the bad camshaft one looks nothing like mine. I posted a YouTube video of my truck running without the valve cover on and it looks to me the camshaft, valve springs, and rocker arm look fine. The truck isn't constantly misfiring, it's at random. It happens a lot but it isn't constant.
Here is the YouTube video of my truck running without the valve cover.

 

[Cowboy Brick]

Just wanna post here for any future people wanting to know the fix for this and say the problem was the O2 sensors. Had them all replaced and truck is running like new.

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