Happens when I do hard rev, release and another hard rev. Think its coming from front not rear. Could it be due to cold? 1989 v12, w Lucas.

 

SPL, did you mean ambient temperature cold or the engine was cold?
RagJag

 

Yes cold outside. just giving as many facts as i can. Not common but if I am aggressive with throttle on and off, once and a while it will give a little pop sound. Maybe once every month or 2.

 

First rev/throttle blip = fuel droplets left in the inlet manifold or even in the cylinder because it is cold.

Second rev/blip immediately afterwards = throttles opened at a moment in the cycle where fuel droplets enter the cylinder and ignite before the intended point.

Greg

 

Agree with Greg, very comprehensive explaination. Greg has obviously not opened a Red prior to typing that one, mmm. The man certainly has a way with words.

Also, the throttle discs MAY be out of time/synch, and this will have 1 engine doing what is does before engine 2 catches up. Bearing in mind it is a "double six", and the firing order makes it that way, so the synchronising of the throttle discs, particularly OFF IDLE synch, is critical.

The dreaded "black goo" inside the throttle bodies will also reek havoc with off idle performance.

Then comes spark plug gap.

Then the list gets picky, and loooooong.

 

I am concerned as to why you would blip the throttle on a cold engine. I would never do that unless it isn't running well. Not having a V12, I really do not have an opinion as to the necessity of doing that.
My 4.0 1996 does not need blipping. Cold starts it goes to 1,000 rpm for about 5 seconds and drops to 800 rpm and to 600 in under 30 seconds. Are V12 engines more cold natured?
RagJag

 

Don't understand why the aggressive revs on a cold engine with cylinder liners. Cold start has the least oil pressure and least amount of oil coating parts with the richest fuel mixture which in turn washes all lube from the moving parts.

 

No cold rev. Cold outside. I warm up before pushing rpms up. The thought of doing damage to v12 has me seeing dollar signs, don't worry.