I had a similar problem years ago on a 3.9 and it was the valley gasket ,leaking a mall amount of water on tickover an causing a slight " Cough" it to me ages to find
 
Looks like the no 3 cylinder issues may have been a distraction from the problem. All works completed to heads etc and now all cylinders firing well and compressions 180 plus.
The engine still needs to warm up and then the whole engine starts to twitch slightly...as in the previously thought "misfire".

Latest guess is flywheel related. There is a sound associated with the "twitch" and it sounds like its rotating. All this was masked by the no.3 problems (dry tappet as well as the other stuff)
The car has been returned so that I can drive it around and see how it develops. It drives well and the symptoms only show at idle.

All good fun....thanks for the ideas etc
 
Looks like the no 3 cylinder issues may have been a distraction from the problem. All works completed to heads etc and now all cylinders firing well and compressions 180 plus.
The engine still needs to warm up and then the whole engine starts to twitch slightly...as in the previously thought "misfire".

Latest guess is flywheel related. There is a sound associated with the "twitch" and it sounds like its rotating. All this was masked by the no.3 problems (dry tappet as well as the other stuff)
The car has been returned so that I can drive it around and see how it develops. It drives well and the symptoms only show at idle.

All good fun....thanks for the ideas etc

Auto doesn't have a Flywheel.

It has a flexplate, and if thats breaking up you'd hear it..

defo..

Give the thing a good drive, take it through the gears, and RPMs.

Report back..
 
Auto doesn't have a Flywheel.

It has a flexplate, and if thats breaking up you'd hear it..

defo..

Give the thing a good drive, take it through the gears, and RPMs.

Report back..
No flywheel? Where does the starter ring gear go? The flex plate is too thin to support the ring gear as it's designed to flex.
 
No flywheel? Where does the starter ring gear go? The flex plate is too thin to support the ring gear as it's designed to flex.
Nope no flywheel. A flexplate is an Automatic's "version" so to speak,, but it's primary purpose is to allow the starter to turn the engine over.

the flexplate is also bolted to the torque converter and can act as a torque dampener for some of the harmonics generated.

very simple, and quite thin..
 
Nope no flywheel. A flexplate is an Automatic's "version" so to speak,, but it's primary purpose is to allow the starter to turn the engine over.

the flexplate is also bolted to the torque converter and can act as a torque dampener for some of the harmonics generated.

very simple, and quite thin..
Funny that, RAVE clearly shows the flywheel & ring gear with a separate flex plate sitting inside a recess in the face of the flywheel. Anything that could support the ring gear would be way too thick to provide the degree of flex required for the torque converter. for sure the flywheel is lighter than on the manual as there is the weight of the torque converter to take into account.
 
Funny that, RAVE clearly shows the flywheel & ring gear with a separate flex plate sitting inside a recess in the face of the flywheel. Anything that could support the ring gear would be way too thick to provide the degree of flex required for the torque converter. for sure the flywheel is lighter than on the manual as there is the weight of the torque converter to take into account.

Rave ain't that accurate..

Not seen that myself.

Autos have a flexplate..

Not a flywheel and Flexplate.
 
Rave ain't that accurate..

Not seen that myself.

Autos have a flexplate..

Not a flywheel and Flexplate.
Flywheel P38 V8001.jpg

Maybe you have never looked closely at a V8 flywheel/flex plate assembly. The gaps in the flywheel are for access to the bolts securing the torque converter to the flex plate
 
THE PLATE WITH THE RING GEAR ON.

ON ANY AUTO IS THE FLEXPLATE.

The lighter, thinner metal frame of the flexplate has an ability to flex across its main axis bending side to side hence the name. Taking up the motion in the torque converter as the rotational speeds change.

The metal frame of the flexplate itself will have multiple machine-cut holes within the body.


The holes are specific to the vehicle, torque converter set-up and potential weight balance of the flexplate.

OBVS the mounting ones.
 
THE PLATE WITH THE RING GEAR ON.

ON ANY AUTO IS THE FLEXPLATE.

The lighter, thinner metal frame of the flexplate has an ability to flex across its main axis bending side to side hence the name. Taking up the motion in the torque converter as the rotational speeds change.

The metal frame of the flexplate itself will have multiple machine-cut holes within the body.


The holes are specific to the vehicle, torque converter set-up and potential weight balance of the flexplate.

OBVS the mounting ones.
I'm afraid you don't know what your are talking about, the flex plate is the thin plate that the torque converter bolts to, the fecking heavy lump with the ring gear on it is a flywheel that has the best part of bugger all flex.
 
I'm afraid you don't know what your are talking about, the flex plate is the thin plate that the torque converter bolts to, the fecking heavy lump with the ring gear on it is a flywheel that has the best part of bugger all flex.

I'm afraid you clearly have no idea..
 

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