Not Tuning Related, Looking for Help on Mechanical Issue

[MarkTucker]

Customer brought in a 2010 Dodge Challenger SRT8 6.1L V8 Automatic for tuning, I am looking for help on figuring out what be my issue.

The car currently has not been tuned. Placed the car on the dyno, to being testing/tuning. And did a tune power run to get baseline numbers before beginning. The car's check engine light starts flashing, so I let out and investigate the issue. The code is a P0305 Cylinder 5 Misfire, the customer then tells me that he has been getting that code for a while now. He has install a new coil pack on cylinder #5. I confirm, that he did place it on the correct cylinder. So I start by swapping the coil from another cylinder to #5 to see if it moves or stays at #5. Start another run, light flashes, I let out and investigate. Still P0305 Cylinder 5 Misfire. So I then, swap the injectors to another cylinder to see if it moves or stays at #5. Start another run, light flashes, I let out and investigate. Still P0305 Cylinder 5 Misfire. So I then pull the spark plugs out to look them over. They all are brand new, I confirm with the customer. He states he just installed them when he installed the new coil pack. The gap on the spark plugs look great. So I swap both plugs from #5 to another cylinder, just for the heck of it. Start another run, light flashes, I let out and investigate. Still P0305 Cylinder 5 Misfire. So I tell him that I want to do a compression test on the entire engine. So I start a compression test on all cylinders.

Here are my results,
#1- 205psi
#2- 210psi
#3- 207psi
#4- 210psi
#5- 250psi
#6- 205psi
#7- 210psi
#8- 207psi

That was not a typo, #5= 250psi.

The test was done with all injectors and all coils connectors disconnected.

I have not done a leak down test yet on the engine, just was very shocked to see how much higher cylinder #5 is over all of the other cylinders.

The vehicle has 80,061 miles on it.

What are your thoughts? The car idles very smooth, it will only register a misfire when driven aggressive(stated by the customer). I have not drove the car on the road to confirm.

[chargerman]

Did the customer keep the old plugs? If so maybe ask to see them, inspect for and signs of oil. My guess would be possible build up of carbon or oil deposites.

[orrwhat]

I had a cylinder #5 misfire. I rotated coil and plugs to #3 and rotated injector to #7. The code happened to follow #7. I went ahead and ran some injector cleaner thru the system and it has cleared up.
My guess for your issue is the compression test is so high, it may not be igniting the mixture. Try running some real high octane thru it to see if it resolves the issue. If so, their may have been a repair to the engine which required replacing the piston and the wrong compression ratio was installed. Good luck.

[Monzsta]

The problem is you have a lobe ground off the camshaft. This sometimes is accompanied by a slight lifter tick. Due to the cylinder pressure being that high it's likely an exhaust lobe. This allows early closing of the valve and reduces the overlap which generates higher pressures. I see it all the time here at the dealership on 5.7's and 6.4's. 6.1's are not as frequent but I have seen a few. I have a '13 Challenger in the bay next to mine missing a lobe. Not sure if the cams aren't hardened properly, oiling, roller locking up and skidding but the end result is always the same.

Pull the valve covers and have someone spin it over while you watch the rockers. Just like the ol' small block chevrolet days. A good time to upgrade if you ask me.

[06300CSRT8]

Before a total tear down, just verify a few things. I leaky and bled down lifter will give the same result as a lobe ground off on the cam. How warm was the engine or how soon after having it running was the test done? When you're chasing a possible bad lifter or bad cam, doesn't matter how hot the engine is to verify its that. I would let it idle for a bit, get up to temp, shut it down, wait only a few minutes, do cylinder #5 and #3 (very easy to get to) and compare.

[MarkTucker]

Well I did all those things you all mentioned.

I did compression test right after a hot engine shut down and I did it with the engine cold. Test results are the same.

Also I did pull the valve cover and removed the rocker assemblies and check pushrods. They all looked fine, and not bent or broken.

I then put the push rods and rocker arms back on, and rotated the engine over by hand. Watching the rocker arm travel on cylinder 1, 3, 5, and 7. And I found that the #5 intake rotor/valve has half the lift as #1, 3, and 7. I did not have a dial indicator to get a correct measurement. But I did measure each spring height as the valve was completely open on each cylinder. And #5 intake spring was 1/4" taller(less valve opening) than all the others. So my finding is pointing towards a lifter or a worn camshaft lobe. Not exactly sure how to prove which one it is.

And at first I thought I was going to have issues with the exhaust valve side, thinking if it was not opening all the way that it was cause high compression test.

But it is the intake side that seems to have a issue. Do you think that I got a higher compression test on #5 is cause of less/zero overlap, allowing for a higher compression read out? I not even sure of a stock camshafts specs, to know if there is much overlap anyways. But other than it affecting the overlap of the camshaft to cause a high compression reading (if that is even what it possible could be), what else would explain high compression reading with intake valve not getting full lift?

[MarkTucker]

The problem is you have a lobe ground off the camshaft. This sometimes is accompanied by a slight lifter tick. Due to the cylinder pressure being that high it's likely an exhaust lobe. This allows early closing of the valve and reduces the overlap which generates higher pressures. I see it all the time here at the dealership on 5.7's and 6.4's. 6.1's are not as frequent but I have seen a few. I have a '13 Challenger in the bay next to mine missing a lobe. Not sure if the cams aren't hardened properly, oiling, roller locking up and skidding but the end result is always the same.

Pull the valve covers and have someone spin it over while you watch the rockers. Just like the ol' small block chevrolet days. A good time to upgrade if you ask me.

I just now went back and read your entire post, yeah I agree. I thought it was going to be a exhaust side issue as well before I got into it. But the exhaust valve seemed to have the same amount of duration and lift on #5 compared to the other. It is #5 intake valve that seems to be the issue.

[Monzsta]

I guess having the intake closing early would give the same result. Make sure you replace that lifter with the cam. They come in a set of 4 with the tray.

[RevHard]

Same thing happen to me ..

after install the supercharge and dyno tuning

In the next day turning on my car and booom my car rough at idle and hard acclaration with code p0300 ( random missfire ) .

After check if have some vacuum leak or bad coil and spark plugs and all fine .

But when bring the car to the mechanic and see if this problem is mechanical issue he told me to wait one day to check it .

After he call me and explained the main problem is from the valve spring ( broken ) and bad rocker arm .

Old 5.7 and 6.1 having same problem ( bad engine head )

[MarkTucker]

Same thing happen to me ..

after install the supercharge and dyno tuning

In the next day turning on my car and booom my car rough at idle and hard acclaration with code p0300 ( random missfire ) .

After check if have some vacuum leak or bad coil and spark plugs and all fine .

But when bring the car to the mechanic and see if this problem is mechanical issue he told me to wait one day to check it .

After he call me and explained the main problem is from the valve spring ( broken ) and bad rocker arm .

Old 5.7 and 6.1 having same problem ( bad engine head )

Thanks man, but I have got it narrowed down to either the lifter bad or camshaft lobe is worn down. Either way, both are getting replaced. And upgrading at the same time.

[RandomEnthusiast]

It always seems to be number 5. My buddy works at the dealership and sees this at least once a month ranging from 05 on up on trucks and cars all the hemi. 90% of the time it's number 5. Makes me think theres and oiling problem with those lifters.

[MarkTucker]

It always seems to be number 5. My buddy works at the dealership and sees this at least once a month ranging from 05 on up on trucks and cars all the hemi. 90% of the time it's number 5. Makes me think theres and oiling problem with those lifters.

That is very interesting. Thank you for that information.

[RandomEnthusiast]

That's what he's told me anyway. It could be less but other people all over have been having the same issues for years. Especially on 5. Don't know why.

[68Poncho]

Probably has something to do with Displacement on Demand. GM has the same issue with that.

[MarkTucker]

Probably has something to do with Displacement on Demand. GM has the same issue with that.

Thanks but this vehicle does not have Displacement on Demand or in Dodge terms MDS.