Erratic running when the engine is cold

[davidkl]

Lotus Excel SE - 1987
For some time I have had problems during the first 3 - 5 miles of any journey. Symtems are loss of power and kangerooing, I nurse the car by changing to a lower gear and giving it some clog, after a little of that nursing the probs go away and all is well until the next time I have to start from cold. Have recently had a full service, changing filters, plugs, with new distributor cap (had a hairline crack) and rotar arm - ahah I thought we have cracked it but NO.
My son thinks that the twin dels need attention, but finding someone to tune those is proving impossible.
Oh wise ones - any thoughts on a carb tuner or has anyone else had similar problems and found a cure?

[robertverhey]

SEs have a number of pollution control measures (switches and vacuum advance) that operate until the engine temp has come up. I'd be checking all of them (well described in service notes section EMB) as well as the fine bore rubber hose that connects them. Might have a vacuum leak somewhere, in which case a cheap easy cure
Robert

[Lotus-e-Clan]

I wouldn't touch the Dellortos yet!

Kangaroo-ing when cold is exactly what happened to my Excel immediately after I changed the plugs.

I haven't got around to properly investigating and curing the problem yet because all I did was change the plugs for new NGKs, so I can only assume it's a plug problem. The old NGKS where shot but it never kangaroo-ed on them. If you still have your old plugs then refit them to exclude this as an issue (I chucked mine away so I can't retry)

If it's the same problem I have then the kangaroo-ing will stop if you pull the choke out. A richer mixture is easier to ignite so I can't assume the carbs are running weak because it runs better on choke. I do think my problem is ignition not carbs, especially as I've heard similar reports following plug replacement with NGKs recently...maybe NGK are having quality issues at the moment?

My intention is to replace the NGKs with the same thin platinum tipped jobbies I have in the Clan which are a much better plug (although expensive).

IF you are then still convinced the carbs are contributing to the problem then before you do anything else check that the accelerator pump levers are VERY free to drop when the throttle is opened. If not then work them loose untill they drop fully and freely and then spray with copper slip.

[kent_racer]

maybe NGK are having quality issues at the moment?

Yes they have. I can't remember how to see that but depending where they were made, they are prone to foul...suppose they selfclean when hot.

[ttedj]

Does it go away as the idle drops (about 50 deg)? This is point at which the advance goes from about 26ish to it's normal 10. May be worth checking the wires going into the distributor don't stretch as they have a habit of breaking internally after many years of bending under advance. The stretching is the external silicon coating showing the wire inside has snapped. I had issues when cold which turned out to be the wires. Solved by changing the dizzy base plate having already changed everything else ignition wise.

Ted

[davidkl]

Thanks four very swift and helpful suggestions. Yes Ted it does right itself after about 10 mins of jumping about and I will ceratinly try the choke trick for quicker resolution.
David

[old tiff]

if you need a carb tune try alvin powel in saltash cornwall. my carbs needed work as the accel pump diaphragm had split i stripped and rebuilt them and achievd a basic set up. alvin then got all the old gear out and set them up beautifully. did not use his rolling road. the car flew the mot on emisions starts and runs very well. i never need choke. 2 pumps on a cold day or 1pump on a warm day and first time starter and 30mpg if i am sensible(not often)