View Full Version : TR2/3/3A TR3 idle speed drop

06-24-2006, 08:52 AM
Good another rainy day morning to all:

1959 TR3A - AUC878 H6 carbs - rebuilt with new shafts - replacement type fuel pump 2 years old.

Car starts idles on choke speed fine no fluctuation all is well, turn choke off, when temp at 185 idles at steady 600 rpm fine, drive away evrything fine - good power. Drive about five miles and wait in line at bank. car idles fine at 600 rpm, after about three minutes of standing idle drops to 500 rpm another half minute later 450 idle gets real splashy, hollow sounding, and getting ready to stall, blip throtte (great term I cannot take credit for)idle right back to a steady 600 rpm after another minute same scenario plays out. Drive car away everything runs fine again, idles at stop signs, and traffic lights A-OK. Once home I let it sit in the garage at idle and after about four minutes it starts to drop again. Is it possible the weather might have something to do with it temps were 91 (F) with very high humidity? Actually it sounds to me like it's not getting enough fuel at idle? Or I guess it doesn't like waiting around and shuts itself off.

I can't get into it until next week (graduation parties) so I was wondering what you all think?


06-24-2006, 09:37 AM
Some things to check (sounds more fuel related than ignition to me too):
Fuel pump pressure
Spark plug visual to see if it is "loading up (too rich at idle)
general carb check

Russ Austin
06-24-2006, 10:08 AM
Hey Harry; That's really slow idle speed, mine idles at 800 to 850 RPM’s great. I think you need to step it up just a tad.

06-24-2006, 10:38 AM
Hi Harry

I agree with vettedag72. Sounds like fuel fixture might be off. I idle my tr4 at about 950 to 1000 (has a 280 deg. duration cam). I'd agree with Russ,try bringing up the idle first.


06-24-2006, 01:34 PM
I dunno. The idle speed spec for the TR3-3B is 500rpm where I have mine set. My guess is too rich in one or both carbs or out of synch.

I would turn each mixture nut all the way in (clockwise)counting the flats as you go. Then as a baseline, set each to the lesser of the two flats. Then lift each piston and note if the idle speeds or slows to determine rich or lean. This must be done immediately after you have the problem to ensure the same conditions. Take notes, it make take a couple of tries to get it right.

Also, have you checked your:
- point condition and gap,
- same for spark plugs,
- lubed your distributor (if you don't know how, then check the shaft for side to side wear)
- wire attachment screws in the cap for tightness
- also if using non-solid wires, check for burning where the screw penetrates the wire, and trim back oor replace the wire if burned

06-24-2006, 07:04 PM
The general thought has always been that if you're carbs are set too rich the idle speed will lower when the engine is hot.

Don Elliott
06-24-2006, 07:59 PM
Check the ball joints on the endsa of the throttle linkage rods. Maybe they are dry. Lube them. Maybe they need to be replaced with new round ball joints.

Don Elliott, original Owner, 1958 TR3A

06-24-2006, 09:28 PM
Summer time. Could be fuel starvation from evaporation. I don't have that problem much in hotter weather but it is a poss.