6 Litre XJS Running Rough
Discussion
Hi All,
My 1993 6 Litre XJS seems to be running a little rough.
This seems to manifest at low revs, below 2000. It doesn't seem to depend on temperature.
As I am out in the Emirates, I am a long way from spares and knowledgeable techies.
Anyone seen this before? All answers gratefully received.
My 1993 6 Litre XJS seems to be running a little rough.
This seems to manifest at low revs, below 2000. It doesn't seem to depend on temperature.
As I am out in the Emirates, I am a long way from spares and knowledgeable techies.
Anyone seen this before? All answers gratefully received.
It's probably best to start with checking the compressions which should find any cylinder or valve issues then pressure test the cooling system to make sure the head gaskets are all good.
Then when you're sure that the engine is in good condition start looking at the ignition system preferably by throwing it away and starting again with a modern aftermarket distributorless system being that all the different factory ignition systems for the V12 are a liability in one way or another even when new and with all now being obsolete and difficult to maintain.
A fuel system problem would probably be more likely to cause problems when starting and throughout the range and worse at higher revs and loads so that's probably the last thing which I'd then start looking at assuming all the above are sorted.
Then when you're sure that the engine is in good condition start looking at the ignition system preferably by throwing it away and starting again with a modern aftermarket distributorless system being that all the different factory ignition systems for the V12 are a liability in one way or another even when new and with all now being obsolete and difficult to maintain.
A fuel system problem would probably be more likely to cause problems when starting and throughout the range and worse at higher revs and loads so that's probably the last thing which I'd then start looking at assuming all the above are sorted.
Many moons ago when I was a techy working on these cars it was not uncommon to see rough running , in the absence of any obvious issues we found that sticking them in first gear and giving them a quick blast up to the red line produced clouds of black smoke and rectified most .
Clearly this has to be done only when road conditions permit and when all systems are up to full operating temperature , fluid levels checked and oil pressure confirmed as OK . Essentially carbon build up due to constant city driving , relative low engine RPM , and rarely driven to full potential .
Clearly this has to be done only when road conditions permit and when all systems are up to full operating temperature , fluid levels checked and oil pressure confirmed as OK . Essentially carbon build up due to constant city driving , relative low engine RPM , and rarely driven to full potential .
LMV600 said:
Many moons ago when I was a techy working on these cars it was not uncommon to see rough running , in the absence of any obvious issues we found that sticking them in first gear and giving them a quick blast up to the red line produced clouds of black smoke and rectified most .
Clearly this has to be done only when road conditions permit and when all systems are up to full operating temperature , fluid levels checked and oil pressure confirmed as OK . Essentially carbon build up due to constant city driving , relative low engine RPM , and rarely driven to full potential .
Italian tuneup works everytime...Clearly this has to be done only when road conditions permit and when all systems are up to full operating temperature , fluid levels checked and oil pressure confirmed as OK . Essentially carbon build up due to constant city driving , relative low engine RPM , and rarely driven to full potential .
tdm34 said:
LMV600 said:
Many moons ago when I was a techy working on these cars it was not uncommon to see rough running , in the absence of any obvious issues we found that sticking them in first gear and giving them a quick blast up to the red line produced clouds of black smoke and rectified most .
Clearly this has to be done only when road conditions permit and when all systems are up to full operating temperature , fluid levels checked and oil pressure confirmed as OK . Essentially carbon build up due to constant city driving , relative low engine RPM , and rarely driven to full potential .
Italian tuneup works everytime...Clearly this has to be done only when road conditions permit and when all systems are up to full operating temperature , fluid levels checked and oil pressure confirmed as OK . Essentially carbon build up due to constant city driving , relative low engine RPM , and rarely driven to full potential .
www.youtube.com/watch?v=CFVOXsVN97Y
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