Lotus Esprit S4 Engine Noise

[sumpster1]

My S4 Esprit has a sound a bit like a diesel at low revs when the engine is under load or when the throttle is "blipped" from idle

The sound has the frequency of pinking but a lower note like a diesel engine

Have investigated with a stethoscope and noise appears to be comming more from top of engine than bottom.

It's only done 34K and no sign of premature engine wear, oil consumption or smoking at high revs.

Performance doesn't appear to be suffering, although this is my first S4 having had an HC S3 before so what do I know, this could just be a feature !!

It sounds perfectly smooth at idle with no undue valve noise.

Anyone have any ideas ??

Thanks

John

[cnh1990]

Maybe bad gas???
Did you run through a tank of fuel and then reset the computer?

I've seen a lot of Esprit's with burnt plugs with the center electrode eroded away (NGK seems to last the longest). They sure don't last long in our cars like a regular car. Also as Mikey mentioned in a previous post check plug cables. I've seen less of these fail but it does happen.

Good Luck,

Calvin

[cnh1990]

Just out of curiosity ever had the valves adjusted?

[wcdeane]

Before you go into things too deeply, you might do well to see if you can find someone to run Andy Whittaker's "FreeScan" program on your S4. That might tell you if your ECU is actually reading knocks from the knock sensor. It can also give you a reading on about 30 other engine parameters that might help isolate the problem. At least you might be able to eliminate engine management components.

If you are lucky it could be something as simple as bad gas. If you have a partial tank, try topping it off with the highest grade of gas that you can find, and see if these faint knocks persist.

Walt...'91 SE