Lotus Elan

Missing elan plus 2

PostPost by: stonks » Thu Sep 17, 2009 5:01 pm

Before I rip its head off, any clues would be most welcome, I have a miss fire, changed the points, cap, plugs, rotor arm.leads, compression checked all 150+psi, checked the cams and have clearances, substituted the carbs. But still it persists. It might be a sticking valve? cannot think what else to do...the dizzy has no wear on the lobes or any wear that I can see

Holding the acc open at around three thousand rpm it cuts in and out but you cannot point to a particular cylinder as the culprit. Perhaps a dizzy change might be the quickest option, any one have a spare / idea. or can supply the model type?

cheers
Glen
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PostPost by: david.g.chapman » Thu Sep 17, 2009 5:47 pm

Might be the coil that's at fault. Try swopping that. I would put sticking valves lower down on the list.

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PostPost by: RichC » Thu Sep 17, 2009 10:11 pm

have you ruled out fuel starvation ?
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PostPost by: RichC » Thu Sep 17, 2009 10:15 pm

just thought, if u suspect sticking valve wouldn't that give you a backfire rather than a missfire ?
yeah?
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PostPost by: reb53 » Fri Sep 18, 2009 6:06 am

Don't have one so don't know, but do +2 s have the anti theft switch that gives you mystery misfires when it plays up ?

Ralph.
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PostPost by: richardcox_lotus » Fri Sep 18, 2009 8:32 am

I would add a Condensor to that list.

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PostPost by: tinker » Fri Sep 18, 2009 8:45 am

Have you checked low voltage wiring at coil and dizzy?
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PostPost by: stonks » Fri Sep 18, 2009 12:10 pm

Sorry the condensors been changed, as has the fuel pump. I'll check out the voltages but I did take off the ballast resistor and run the coil on full 12volts. still the same. its a bugger.
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PostPost by: alaric » Fri Sep 18, 2009 5:20 pm

Hi. Air leak? Either via the servo connection or the headlight vacuum connection. Just a suggestion.

Sean.
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PostPost by: gjz30075 » Fri Sep 18, 2009 8:08 pm

Did you check for any wobble in the distributor shaft? If you set the points at .015, and there's .015 of wobble, then the points will randomly not open.

Up and down movement of the shaft shouldn't be excessive, either.

Greg Z
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PostPost by: zeteclotus » Sun Sep 20, 2009 7:33 pm

bad new plugs? Had bad new champions before now on more than one occasion.

Try NGK one hotter than the standard. worked for me...
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PostPost by: Lincoln62 » Tue Sep 22, 2009 1:31 am

You might be able to narrow your search by comparing the colour of the spark plugs. If there is a problem in one cylinder it will be obvious.

Peter
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PostPost by: stonks » Thu Oct 01, 2009 7:51 pm

I have changed the plugs - again, removed the dizzy again, changed the rotor arm, condensor, and points again, the cap is new. The dizzy has no noticeable wear, either axially or vertically. all the lobes are regular and unworn, i have Refitted it and yes its marginally better. but its still not right, next stop will be to replace the points and condensor with a contactless unit and another new but non ballasted coil, I can then rule this area out full stop. BTW also removed the base plate and checked & lubed the weights - replaced the LT wires. New plug caps and the leads were replaced at one of my other earlier attempts. Also have replaced the carbs with some pre loved ones. better but not quite right. Thanks for all your ideas though.
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PostPost by: paddy » Thu Oct 01, 2009 7:59 pm

Have you tried looking at the timing with a strobe? It gives you a very good idea of whether or not the distributor and everything else is in good shape.

Even with a perfect distributor you can get an alarming amount of scatter in the timing as a result of poorly adjusted timing chain, worn skew gear, or excessive jack-shaft end-float. You may also see "missed" sparks synchronised with a stumble in the engine.

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PostPost by: CBUEB1771 » Fri Oct 02, 2009 2:29 am

How about the earthing strap between the engine and chassis? I was once asked to help a friend diagnose rough running. I was looking it over in the early evening and was amazed to see arcing at a bad engine earth connection. Replacing the earth strap solved the problem.
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