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Runs rich on one side

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Hi Guys,

The Esprit starts with a small puff of oil smoke on the right side: this has happened ever since the mutton-heads at the only Lotus dealership in Ontario screwed up a timing-belt change and had to have the head rebuilt on that same side. I assume this to be a valve guide or valve stem oil seal problem, and before anyone says anything about it, I have been living with it for close to two years and have not the energy nor the will to fight with the dealership to rectify this. The less I take the car there, the better, and unless anyone can tell me of a really good reason why I shouldn't live with this minor issue, I'll just enjoy the car and leave it until a full rebuild of the engine some day in the future (Mike Sekinger, you'd better still be around smile.gif )

No, the (again minor, I hope) problem I am having that I wish to rectify is this: the car starts wonderfully and idles perfectly; within roughly 20 seconds of start both sides start to run rich, on cue, as I believe they should. Then after about one minute, the left side leans out nicely (I am making these assumptions based purely on the exhaust colour and odour), and the exhaust is clear. The right side, however, remains in "rich" mode for a very long time. This observation has been made at idle, but even after some driving the right bank seems to remain visibly rich. It does eventually settle to the point of displaying no visible exhaust, but it seems this happens only after about 10 minutes of driving.

I have checked the plugs (I had an injector replaced on that side last year - it was apparently leaking), but they are all clean save for the number one plug which shows a bit of oil deposit: I assume this is the result of the problem detailed in the first paragraph. There is no fuel odour on the number one plug as there had been last year before the injector was replaced on that cylinder. I installed a fresh plug in the number one right side cylinder (the previous one had not even been properly gapped, another detail which indicates the quality service I receive from the only dealer around) and did a check, but no change in right cylinder bank behaviour at start idle was observed.

Any suggestions?

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I would start by suspecting the oxegen sensor, but a diagnostic rig should be able to pinpoint it.

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Hi Patrick,

I would concur with your thoughts on the oil smoke - it does sound as though you have a dodgey stem seal. Although I understand your reluctance to tackle the same dealership, in likelihood it will only get worst over time. :D

Other than odour and visible signs, how are you determining the rich running of the RH bank? Are you using a OBDII tool?

Cheers,

Mike S

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Thanks Guys,

Mike I have only used the visual/nasal method for my running rich determination. I do have an OBD tool, however, and can look at it today to see what sort of comprehensive answers I can get from it. It is a pretty cheap model, so I am not sure what it can show me. What should I be looking for?

On the stem seal front, I think its replacement is a big job, no?

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Hi Patrick,

On the rich running front, thinking this through the best way would really be to get the exhaust gases properly analysed. This will give you a far more dependable result than trying to determine what is happening via the o2 sensors.

Depending on the exhaust internal structure, it might even be sensible to remove the exhaust system and take the sensor readings directly from the cat outlet. You should also consider that if the engine is burning unwanted oil, then your catalysts are also likely to have a reduced life.

To replace the offending stem seal(s) you would need to partially dis-assemble the valve gear (camshafts, tappets, valve springs and retainers). This job is only really possible with the cylinder head removed from the engine.

It would be prudent to check the compression of the affected cylinder to check that the valves are sealing properly and that you don´t have problems broader than just the stem seal.

Cheers,

Mike S

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Hi Mike,

Thank you for all of the good information. I admit I was concerned that the oil burn might be hard on the cat on that side. Having said that, I don't suppose I will drive it enough to deteriorate a cat before I do an engine rebuild anyway.

The cylinders have been checked for leak down as recently as last spring when the injector was replaced, and the shop claims they are good, so unless the stem seal problem can create a valve sealing problem, I suppose the cylinders are probably still okay.

I think both of these problems are likely well outside my own ability to rectify, unfortunately, which means taking the car to the dealer... ugh.

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