Engine rocks - honestly but side 2 side rocking...

[damedaphne]

Hey everyone - shes been fine upto the point I started putting refrigerant gas into the air con and then I have developed a rocking motion at idle.

With the air con on its worse, i've checked the plugs as well. Cyl 5 plug was oily so I swapped to cyl 6 and swapped the coil pack with cyl 4. So the next time i'm out I will check again to see if the oily plug swaps cylinder. The engine sounds like its missing a beat and its blowing really badly... Would a blown exhaust cause rocking of the engine at low revs? I mean it all smoothe's out when rev'd except when I am at 1900-2000 rpm cruising at 50 in top - then I get a real bad vibration throughout the car....

Have anyone of you experienced anything like this? She's drivable...

[davidr]

It sounds to me like you have dropped a cylinder for some reason such as a failed plug, lead, injector, coil pack, valve etc.
Which model and engine do you have?

[poprivet]

Having the a/c on will load the engine hence make the problem sound worse. If it's an AJ6, with the engine running carefully and individually pull each plug lead one by one, it will falter if that one is ok. When there is no difference you have found the one at fault.

I get the same problem if my 3.6 has stood for a long time, one of the injectors gets sticky. If it's an AJ16 a faulty coil pack is likely as David suggests.

The exhaust manifolds do crack but wouldn't cause a rocking motion.

[damedaphne]

Cheers gents - thank you for your time.

I have thursday night to test the coils/plugs etc.

Its AJ16 4.0ltr engine, Daimler Six LWB. I think that ive been using her more now than ever it was bound to throw some issue up.

I will keep you posted of my findings.

Jamie

[damedaphne]

Pulled the plugs tonight as Thursday night was a no go....

No 6 was fine as was No5 but No 4 was clean... so the award goes to a faulty coil!!!

As I have inspected them all and tested each one with a meter. I can only assume that the secondary winding has gone in the coil but I haven’t the time or patience to test it that thoroughly.

I going to change the whole set as I’m not sure of the others. At least I have gained 5 spares... they are all Lucas and cracked down the sides.

Scanning the web for replacements I’ve noticed gaskets are available. I don’t have any fitted so I’ll be getting me some of them!

Thank you for all your input.

Jamie

[davidr]

To confirm your diagnosis try moving the suspect coil to another cylinder. If the misfire moves with it then you've got your culprit!