running cold

[Member 10617]

Just got back from an 80 mile run north of here and back. Great ride, great day... but cold.

The car was just a little hesitant each time on acceleration, unless instead of a steady pressure down on the accelerator I did it in small increments. (Never tried that before.)

I read elsewhere here to day that in cold weather, some of your richen the mixture by two flats. I tried that, and it seemed to make a little difference, but didn't cure the slight hesitation on acceleration.

Also, it was cold enough that my car ran at between 182 or 183, more or less, all the way.

Since the hesitation was on acceleratin, I wonder if running 20 weight oil in my dashpots is a bit too heavy in such cold weather. Would MMO be a better choice for "winter" driving?

Any other suggestions?

 

[TR3driver]

So did it get better or worse when you richened the mixture a bit?

My guess is that you need more mixture, not less, (meaning heavier oil in the dashpots) but that's just a SWAG.

According to Weather Underground, Lexington is around 50F today, which shouldn't be enough to be a problem. Could be that your ignition is marginal for some reason; sometimes acceleration will show up problems that don't appear at cruise. Are your plugs gapped to .025" ?

 

[Member 10617]

When I richened the mixture up a bit, it seemed to get a little better. Once cruising, the car performed great -- smooth as silk -- but when I slowed down and then speeded up, there was a bit of a hesitation (not much, but noticeable).

What is different from recent rides when I didn't notice this: (1) colder, (2) have lost access to ethanol free gas so I am on my first tank of ethanol.

OK... I'll keep the 20 weight on the dashpots and look for some other cause

The weather in general is around 50F, but driving down the road and in slightly higher elevation north of Lexington, the temperature was probably down in the low 40s. In an open car, it seemed even colder!

You don't think the car running in the low 180s range could be part of the problem? In the summer, it runs at 185-186, always, and I don't have this hesitation problem.

My plugs are almost new and are gapped to .025.

In another thread, I talked about replacing the wires that run to my generator. They are suspiciously small gauge, and have been cooked pretty thoroughly by the manifold. Don't know if this is the problem, or part of the problem. But as soon as I receive 44 strand from British Wiring, I am going to change out all the wires. I think you said in one of your responses that the 44 strand wire will perform better than the 28 strand wire that may be in the car now.

 

[Geo Hahn]

I don't think a few degrees cooler at the thermostat would make any difference.

I also don't think the condition of the generator wires would affect running (you could pull them off and the engine would still run fine... for awhile).

If you feel like experimenting you could put 20W50 into the carbs and see what happens (that's what I use year-round).

 

[bobhustead]

You seem to be going in the right direction. try richening a couple more flats
Bob

 

[Member 10617]

OK, will do. I'll keep the 20w in the dashpots, and richen it by two more flats.

I am sorry, however, to lose the non-ethanol gas and can't help but think that it must have something to do with my changed performance.

 

[TR3driver]

'Oxygenated' fuel will definitely require a richer mixture. Also, your filling station may not have switched to 'winter' gas yet, which is formulated for better performance in cold weather.

IMO, 5-10 degrees on the temp gauge doesn't make any difference at all. However, colder air going into the carbs will definitely make a difference. Cold air is more dense, and hence needs more fuel per unit volume to keep the same mixture. So leaner because of the E10, plus leaner due to cold air, might well be enough to affect performance at least slightly. Especially if it was tuned a bit lean before.

 

[glemon]

I would agree about keeping the 20w in the dashpots. I have tried all sorts of stuff in the dashpots and it didn't make much if any difference in running characteristics, except when I tried WD40 (30 years ago, thought it would give the car "instant throttle response").

I would also suggest adjusting the mixture further, I am one of the guys who would richen up the mixture a bit in the winter back when I had daily driver year round cars with SUs. Back when I ran Sprites and it got real cold couldn't get them to run without the sort of hesitation (even when fully warmed up) you describe without a mixture adjustment. I also agree with Randall, not that cold that you should have much of a problem unless you started out a little on the lean side. So there is an off chance you may have some sort of ignition/weak spark kind of issue.

I will add that of all the various cars I owned, MG, Spridget, TR, the lusty 4 cylinder TR motor seemed to be about the best in adjusting to hot, cold, whatever conditions you threw at it, nice cold starting cars, mine did fine in double digit below zero temps many times.

 

[Member 10617]

Problem solved! It was not an ignition problem, nor a temperature problem, nor a mixture problem, nor even a problem with the weight of the dashpot oil. But it was a dashpot problem.

The oil levels in the dashpots were low. I brought them back up to the required level, took the car for a test drive, and had no hesitation.