TRExp

TR6 Tech Forum

TR6 idle rises as I drive the car - also, Oil pressure question

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

tylerwerrin Tyler Werrin
Santa Monica, CA, USA   USA
1972 Triumph TR6 "Lil Vroom Vroom"
Hi guys,

As I've been driving my TR around in the nice weather, I've noticed a few things:

1) As I drive the car around, after about 20 minutes of runtime, I've noticed that my idle climbs to around 1000-1100. If I let off the clutch, the idle will drop back down to a normal-ish race... but soon as I drive a bit and come to a stop, the idle rises right back up. What could be causing this? I've fiddled with my idle set screws but the problem persists.

2) The oil pressure on the car drops to the "2" on the gauge, (and even a little lower) while idling. Is this normal? Or is my oil pump getting ready to die on me? I am getting the feeling that the oil is heating up and getting really thin (due to the higher idle, which incidentally causes my temps to rise a bit above the middle of the temp gauge) which is causing the drop in pressure but I'm just not sure; pressure is great for the first 20 minutes or so, in the 50's.

I'm gonna take a break from driving around til I fix these problems; I suspect they are all interrelated, but since I don't have much experience with these cars (other than the one I own of course) I'm not exactly sure what "perfect" is, or if my car is a ticking time bomb!

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
Not the only thing by any means but that idle could be affected by a malfunctioning Throttle Bypass Valve or one that's not properly adjusted.

tylerwerrin Tyler Werrin
Santa Monica, CA, USA   USA
1972 Triumph TR6 "Lil Vroom Vroom"
I suppose it could be malfunctioning, but I did just rebuilt the carbs (new valves included) so I'm a little reluctant to dig in considering they are mostly new.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
If the components especially the diaphragm within the TBV are either new or in good condition and you used the correct gasket between the TBV and carb, then as far as the TBV that just leaves the adjustment aspect I mentioned..., you may want to keep that in mind if you fail to find anything else.

rjc157 Avatar
rjc157 ralph c
pearl river, NY, USA   USA
If Ken doesn't know rest assure no one else does I'm thinking it's some kind of vacuum leak causing the idle to fluctuate

tylerwerrin Tyler Werrin
Santa Monica, CA, USA   USA
1972 Triumph TR6 "Lil Vroom Vroom"
I pulled the temperature compensators off the side of the carbs; one of the plugs was kinda sticky, so I cleaned it up. I'll take it for a spin again tomorrow; I'll attempt the TBBV adjustments after I get through with the road test tomorrow.

It seems to make sense, that the compensator would be the issue; the idle rises as the heat under the hood increases. I'm using an electrical fan, so maybe because the fan isn't running all the time, (like the mechanical one), there isn't as much airflow as there should be.

I'll also try idling the car with the hood up for a few minutes after driving around for a while, to see if the additional airflow from the open hood drops the idle back to normal.

QUESTION though: can I just disable the compensators altogether? Just plug up the hole and call it a day, if they are indeed the problem?



Edited 1 time(s). Last edit at 2018-02-01 02:30 AM by tylerwerrin.

Fogspawn, CA, USA   USA
1974 Triumph TR6 "Machine"
valuable points from Ken and ralph c. I have rebuilt carbs twice, rebuilt throttle bypass valves three times,
and also replaced temperature compensators on carbs, where I discovered I had left out the0ring
on TC of rear carb.
the rise in idle speed may be normal. My 1974, and info I have for 1972 says you have Thermostatic
vaccuum valve in the top radiator hose, with a vac line going to the distributor.
my read is that when we start the car, it runs needing choke action to keep it going until starts to warm up,
or until you can get to a road free of stop and go for a bit...
when you come to a stop after a merry stride, idling at stoplight, ...if the coolant temperature reaches a certain poimt, the thermostatic switch works, increasing the idle speed, drawing more air to cool ...
(I may be all wet on that point, but that is what I have picked up somewhere.
Am saying to some extent this increase in idle is normal... but also that condition of Throttle Bypass Valves and
Temperature Compensator valves, and their proper allottment of gaskets and O rings are essential
to consistent running.
actually increase to 1000/1100 rpm might be normal, if it is in response to elevated coolant temperatures,
and if conditions change (reduction in coolant temp), the idle speed may drop back to more normal 850give or take..
Poorly adjusted TBVs will cause idle run up as well, but I think will go higher, like to 1500 rpm plus...
Vac leaks, from any source, will prevent decent running.

The oil pressure... "2" on gauge indicates 25 lbs... which is ok at idle, what is pressure at 2500 rpm? mine indicates
above 50 pounds...
sorry my input is so long winded, but have been through same stuff recently.... and found faults in my own work,
correction each one contributed to better running.
i think some parts of your concerns may actually be normal behavior. the oil thins owing to high coolant and engine temperatures.
I notice in cold weather my engine takes a long time to come to temperature, cold here being 50f, but at 70f ambient, it comes up much quicker and will hit that magic point where idle jumps from 850 to 1000 plus, until I can get car moving
again. and when doing that, coolant tones down, idle will be more normal until temp rises...
point being that the engine behavior will vary with ambient conditions...Engines of yore do not have todays auto computer
controlled adjustments ...
w

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
tylerwerrin Tyler Werrin
Santa Monica, CA, USA   USA
1972 Triumph TR6 "Lil Vroom Vroom"
The Bypass valve diaphragms are both new; car probably has 100 miles total on the rebuild, which was done about 8 months ago... doubt they've gone bad in that amount of time. They could be mis-adjusted however, so I will investigate.

I don't actually have the thermostatic switch setup to the distributor; i capped off the vacuum port when I moved to an electric ignition.

Good to know that oil pressure is OK at idle; when driving it's in the 50s, so thats good to know.

I suspect that the temperature has something to do with the idle climbing; whichever is causing which, I'm not sure. As I mentioned, I am using an electric fan, and it's been warm lately, so perhaps idling in traffic is causing the underhood temps to rise, the fan doesn't kick on til coolant reaches 185 (or so the specs of the switch say) so the compensators getting opened fully seems like valid logic.

But again, Poolboy knows best; i'm sure in the end it will be the bypass valves, but if its one thing you've taught me Poolboy is to go down the list and tick off the possibilities!

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
Like I said, earlier the TBV isn't the only thing that could account for the change in idle.
It's pretty easy to check and one way or another eliminate it as a suspect.
As far as the Temperature Compensator..all I can say about it is that both of the major carb rebuilders (and I'm not one of them) disable it..Same for the TBV.
Unless requested otherwise I make both of those subassemblies function, but I have no objection to disabling one or both.. Sooner or later the TBV is going to act up if active and frankly, I see no practical advantage of having the TC active...Active, it can confuse and confound a person when setting the idle adjustments if it begins to cycle during the procedure.
Anyway, all I'm saying if IF the underlying cause which could include everything mentioned so far by the previous posters, check out the TBV, gasket and adjustment....I've chased minor irregularities like this before and sooner or later found it...you will,too.



Edited 1 time(s). Last edit at 2018-02-01 08:52 AM by poolboy.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Fogspawn, CA, USA   USA
1974 Triumph TR6 "Machine"
oh, and 100 miles only since the rebuild and getting back to road. One would still be in the
"tweaking " stage I think, gradually adjusting things, (in some systematic way hopefully)
until rendering all the harmony necessary for the best running of engine...
"Patience, young Skywalker, has many schoolhouses..."
w

Fogspawn, CA, USA   USA
1974 Triumph TR6 "Machine"
ach! quoted wrong, it is
"Patience, Little Grasshopper, has many schoolhouses..."
w

tylerwerrin Tyler Werrin
Santa Monica, CA, USA   USA
1972 Triumph TR6 "Lil Vroom Vroom"
Yeah, I'll keep at it; thanks guys!

I'm going to try and at least make the TBV work, since I paid for it and installed it. As for the compensator... do people who disable it just tap the vacuum port and plug it with a bolt?

The TBV I could see just using a piece of gasket/rubber and plugging the vacuum holes... and screwing the unit back down, sandwiching it, and eliminating it's need. I think I saw your write up on that Poolboy, last year, while I was rebuilding the carbs.

I must say it is very nice having the car on the road; although modern cars certainly have spoiled me! Even my 84 Jaguar (with a Chevy LT1 and dual exhaust) is quieter than the TR6, and much more comfortable for my size. However, the visceral thrills of being so low (coupled with surprisingly good acceleration) can't be beat!

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
The shops that disable the TC, just turn the tiny nyloc nut on the bimetal strip all the way clockwise and close the adjacent brass idle mixture trim screw.

ng19delta Avatar
ng19delta Scott Roberts
Merchantville, NJ, USA   USA
1974 Triumph TR6 "Gypsy Rose T..."
I followed Buckeye Triumphs directions for my carb rebuilds, and Poolboys advice, and the only problem I've had has been finding good days and long roads to drive! (knock wood)

Scott

grendal14 Frank Guagenti
Asheville, NC, USA   USA
1975 Triumph TR6 "Pumpkin"
2001 Mazda MX-5
I had the same problem. It turned out to be a kink in the choke cable. If you stab at the accelerator in neutral does it come back down ?

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

To add your reply, or post your own questions




Registration is FREE and takes less than a minute!


Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster