Kai Demarco

The main thing is I get heavy engine vibrations at idle around half the time the car is running, despite RPMs always being stable. I have also been having a recurring misfire on cylinder 1. No noticeable performance drop but usually comes back either immediately or within a a couple weeks maximum when I clear the code.

For the misfire, I have verified proper spark on the plug, I have checked for injector ping using a noid light, I have verified proper fuel pressure, and I have checked compression on cylinder 1 and 2, 145 and 130 respectively. As for the engine vibrations, I have definitely thrown parts at it. I will list all the parts I have replaced in the last year, some are for the heavy engine vibrations, others were for the misfire, and some were done for other reasons however I included them anyway. So far I have replaced:

-all ignition components from the rotor and ignition coils to the spark plugs (done twice within a year, the second time using highest quality components)

-engine and transmission mounts

-switched to 12 hole injectors

-replaced exhaust system from manifold to tailpipe (replaced manifold gasket as well)

-both 02 sensors (Walker Brand)

-MAP (NTK), IAC (Duralast), CPS (Walker), and TPS (NTK) sensors

-cleaned throttle body and replaced gaskets

-fully replaced vacuum lines

-replaced all major battery cables

-replaced harmonic balancer

-sanded grounds

-replaced distributor pickup coil

-reset ecu with each major change

-checked wiring harness at common chafing points for worn wires

My remaining theories currently are:

-I have heard a lot of people saying that aftermarket ignition coils always have problems. I am thinking about trying to find a genuine Mopar ignition coil to see if it could fix things.

-possibly a flexplate issue/something being out of round? Can flexplates cause problems at idle?

The weird thing is that gripe I have is that the heavy vibrations happen probably around half the time at idle, the other half of the time it idles perfectly. Again RPMs are not changing despite the vibrations, and temperature is not a factor when it idles rough. I assumed these vibrations and the misfire were connected, however I unplugged the spark plug wire from cylinder 1 and it did not cause the heavy vibrations like I assumed it would. Another note, these engine vibrations pretty much go away if I rev the engine at idle.

However my main theory is now internal engine issues. Valve or lifter issues? Last year I took it to a shop for both the misfires and rough idle, they said they had to take apart the valve cover, yet it fixed nothing. As soon as I pulled out of the shop both issues came back within an hour. Advice on how to check for these problems would be greatly appreciated.

Video of my engine at idle:

https://drive.google.com/file/d/1Oj3...ew?usp=sharing

^If you watch the power steering reservoir, you can really see how much the engine assembly shakes. Not sure if this is the normal amount or not

Video of my exhaust ( Ignore the water, i just washed it):

https://drive.google.com/file/d/1BjP...ew?usp=sharing

cruiser54

Look here:

NCTOM0966

Since you are chasing a sporadic issue, this suggestion is a bit of a reach...
I have seen a a failing harmonic balancer do this on many engines. When the elastomer band between the hub and the outer ring starts to fail, the outer ring can slip and cause vibration. Its conceivable that it can move around and make the vibration come and go. Without a doubt it will make one vibrate. It only takes a second to hit it with a light and take a look. Look for the rubber to be swelled up from oil soaking into it, or dry rotted and cracked up. This picture shows how much one can slip and rotate. The counter balancer will be in the wrong area to cancel out crankshaft vibrations. You can always put the number one clyd. at top dead center and look at the timing mark. If the timing mark is at the bottom rotate it to TDC again to make sure you aren't 180 degrees out, and check the timing mark again.

NCTOM0966

My bad, I just saw where you had already replaced it.

awg

I would closely inspect the internal parts of the distributor, including cap for witness marks that may indicate excessive shaft freeplay which can happen when the internal bushing or bearing, I cant recall which, becomes worn on high mileage engines.

If the dizzy shaft has excessive freeplay, it probably will be detectable by trying to wobble it, as it should have no play

Its a long shot, but i did see a fellow OH his dizzy due to this issue, and added a grease zerk while he was at it, easy thing to check