2long Posted October 29, 2018 Report Share Posted October 29, 2018 I have reached a fairly happy medium with my TR2, taking it out for a good shakedown cruise at least every second weekend while I am sorting the Doretti. But my issue is this: When I start the car from cold after the two week wait (using the choke at first), it runs fairly smoothly while at a constant rpm as it warms up. But during warm up, any blip of the throttle (with clutch engaged) causes a stumbling increase in rpm. If I am driving it in this state, it stumbles as I accelerate. But, once the car is fully warm, it then revs nicely and pulls strongly under load and feels as it should. I did not think the warm up period would lack a smooth throttle response if the choke is used. Here in Hawaii the temperature does not really go much below 60 degrees, so when sitting it does not ever get cold like a car does in winter climate. Any ideas? Dan Quote Link to post Share on other sites
ctc77965o Posted October 30, 2018 Report Share Posted October 30, 2018 Does it do same regardless of choke position? I start with choke here in Malaysia, but can push choke in halfway as soon as it fires and then fully in after driving for a few mins. Quote Link to post Share on other sites
2long Posted October 30, 2018 Author Report Share Posted October 30, 2018 Yes, regardless of choke position. I usually push the choke back in after a minute or two, and then wait for it to fully warm. This warm up period is when the stumbling occurs. If I start the car up the very next day after use, even after it has fully cooled overnight, the symptom is not there so it must be related to sitting for two weeks. Just wondering what is going on so I can possibly avoid it or remedy it. Dan Quote Link to post Share on other sites
ctc77965o Posted October 30, 2018 Report Share Posted October 30, 2018 Hmm...only after weeks of storage?? damp ignition?? Quote Link to post Share on other sites
Ian Vincent Posted October 30, 2018 Report Share Posted October 30, 2018 Tired fuel? rgds Ian Quote Link to post Share on other sites
boxofbits Posted October 30, 2018 Report Share Posted October 30, 2018 (edited) Hi Dan when did it last have a general engine tune as a lot of the basics could be ruled out by carrying out such? It could be anything from dirt or rust residue getting to the carburettors, distributor cap, leads, points and gapping, , plugs, condenser etc. Doing this first might rule out a lot of possible causes, presuming this hasn't already been done. Kevin Edited October 30, 2018 by boxofbits Quote Link to post Share on other sites
ianc Posted October 30, 2018 Report Share Posted October 30, 2018 Letting an engine run to warm it up does the car no favours, it just washes oil off the inside of the bores. Best to start the engine, then drive the car on the road using moderate throttle. This will warm the engine more rapidly and so minimise use of the choke. Ian Cornish Quote Link to post Share on other sites
Motorsport Mickey Posted October 30, 2018 Report Share Posted October 30, 2018 (edited) Carburettor dashpot oil too thick, drain it out and replace with thinner. Engine cold thicker oil = greater resistance to vacuum, causes stumbling, when the engine warms up the oil thins and the carb performance returns to normal. Mick Richards Edited October 30, 2018 by Motorsport Mickey Quote Link to post Share on other sites
Rob Salisbury Posted October 30, 2018 Report Share Posted October 30, 2018 Use of the choke is a bit of a lost art due to modern cars not having chokes at all, but it's dynamic not static, one position does not suit all conditions, starting from completely cold you may well need full choke, but this needs to be progressively decreased as the engine warms up, but may also need adjustment (increase or decrease) according to various load requirements as the car is driven and not left to warm up standing still, as Ian says, you're doing the engine no favours with it standing still. Cheers, Rob Quote Link to post Share on other sites
Peter Cobbold Posted October 30, 2018 Report Share Posted October 30, 2018 3 hours ago, Motorsport Mickey said: Carburettor dashpot oil too thick, drain it out and replace with thinner. Engine cold thicker oil = greater resistance to vacuum, causes stumbling, when the engine warms up the oil thins and the carb performance returns to normal. Mick Richards +1 Quote Link to post Share on other sites
stillp Posted October 30, 2018 Report Share Posted October 30, 2018 5 hours ago, Motorsport Mickey said: Carburettor dashpot oil too thick, drain it out and replace with thinner. Engine cold thicker oil = greater resistance to vacuum, causes stumbling, when the engine warms up the oil thins and the carb performance returns to normal. Mick Richards It's OK the next day though Mick, and he's in Hawaii so never gets very cold.. My guess would be either moisture on the ignition leads/distributor cap/coil top, or condensation somewhere in the fuel system, that takes a couple of weeks to settle to somewhere where it can cause a problem. Pete Quote Link to post Share on other sites
barkerwilliams Posted October 30, 2018 Report Share Posted October 30, 2018 "....during warm up, any blip of the throttle (with clutch engaged) causes a stumbling increase in rpm" Could this be caused by sticky weights in the distributor advance? Freeing up with use and when hot. Easy to check when cold by removing distributor cap and rotating the arm and checking it springs back to rest nicely. Alan Quote Link to post Share on other sites
boxofbits Posted October 30, 2018 Report Share Posted October 30, 2018 (edited) 3 hours ago, barkerwilliams said: "....during warm up, any blip of the throttle (with clutch engaged) causes a stumbling increase in rpm" Could this be caused by sticky weights in the distributor advance? Freeing up with use and when hot. Easy to check when cold by removing distributor cap and rotating the arm and checking it springs back to rest nicely. Alan I doubt that Alan although worth a look..It would probably still rev freely but without a smooth advance. Kevin Edited October 30, 2018 by boxofbits Quote Link to post Share on other sites
ChrisR-4A Posted October 30, 2018 Report Share Posted October 30, 2018 Air leaks on inlet manifold gaskets which disappear as engine warms up and metal expands. Try checking nut tightness before resealing/replacing gaskets. Chris Quote Link to post Share on other sites
2long Posted October 30, 2018 Author Report Share Posted October 30, 2018 Thanks much for all the input. I do notice that after the two week storage period, if I take it home and start it up the next day it starts on the button and revs nicely right away, so it must have to do with sitting for a spell. I make sure never to wait more than two weekends before I get down to the storage stall and go out for a spin, but I guess every week would be better. I am well aware of the maxim that frequent usage is the best medicine for these machines ........ It would be nice if I could pinpoint just what is going on though. Cheers Dan Quote Link to post Share on other sites
ianc Posted October 30, 2018 Report Share Posted October 30, 2018 Just a thought: do you use the priming lever on the fuel pump to fill the carburettor float chambers prior to attempting to start the car? If not, it will stutter into life on cylinders 1 & 2 then, as the rear float chamber fills, will pick up cylinders 3 & 4. Ian Cornish Quote Link to post Share on other sites
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