Ls Not Running Too Smoothly

[Paulrwales]

Hi

Our LS seems to be pretty reliable, due a service about now. However the other week we had just under half a tank of fuel and it appeared like it wasn't running as smooth so we filled her up, incase it was a shortage of petrol somehow. It's happened since. Starting, running, acceleration is fine. It is difficult to describe, just appears to be intermittent thing either hot or cold. Normally the needle stays at about 600rpm but it drops down or goes higher (without air con on) Its going in next week for the :shutit: service but could it be a spark plug or something like that? It was last serviced June 02 and only done about 8000 miles since. Thanks :D

[lexuslexus]

The LS400s do have a weakness with their spark plug leads. They are the thin type and seem prone to shorting through the insulation. Make sure that they are in their clips, look for 'burning' ( usually white ) marks where the leads touch each other. try putting some insulation tape at these points to keep them apart. Clean them up. Also carefull pull back each lead off its plug and check for signs of sparking to the plug, they can burn completely away here. The offside ones are much harder to get at, you need to remove the inlet trunking. Lexus wanted £252 +vat for a set. Cars like the Nissan mirca have the same thin leads and can be made to fit with some care/adaption. The only good news is that you can usually persuade your local Lexus Service dept to plug in their 'computer' which will show up any failing lead and tell them which one.