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TR6 1971 TR6 won't idle.

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BJones

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My tr6 wont idle. It hasn't since I bought it. Even after it is warmed up, if I pull up to a stop light I have to either rev the engine or pull out the choke to keep it from stalling. I keep reading on here that 99% of all carb problems are actually ignigtion problems, so can someone help me out. I should have the next few nights to try and get this working. With the choke out a little I can get the engine to idle around 1100-1200 rpms. I have borrowed a timing light and it is reading +21. I think my bently manual says I should be at +4. Am I right? My father who hasn't messed with the timing of a vehicle in over 20 years attempted to help me and we started to turn the distributer we were able to get the timing down +16 before the vacuum advance got in the way. When doing this, the engine actually started running worse, so we put it all back. Can someone help me with even where to start? Help me find TDC and go from there? I have checked all the plugs and they are gapped correctly and it does not appear I am running to rich or lean. The PO did install a Pertronix electronic ignition and I have the original ZS. The car runs great when I am not sitting still.

Please Help!
 
I'm gonna let someone who is more familiar with the vacuum pots on your years help you. I know I set mine by total advance at 3K at 32 degrees.

However I am going to suggest a little carb inspection. Get it running, then with a can of carburetor cleaner(with the little plastic tube) spray around the base of the carburetors, intake manifold and any vacuum hoses that come off of the carburetors,manifolding. Might want to actually take a pair of hemostats or fine vice grips to pinch off the vacuum hoses to remove that circuit from the engine running.

If you experience any change in running speed or rhythm explore further.

Then remove your carb tops, one at a time and examine the rubber diaphragms carefully and up closely. Possible one or both of them has developed a rupture. When you put them back in put oil in the tube per recommendations. As you've got the air filter body removed from the face of the carbs(easier to work on/inspect the carbs) fire it up, then with a small screwdriver lift each piston slightly to see if idle speed improves. You should be able to set your idle speed with the stop screws.
 
If your '71 is like mine then you will see numbers marked on the crank pulley that indicate timing. It is also marked "before" and "after." I wasn't clear whether you are at 21 deg. before top dead center or after. Hopefully "before" since 21 deg "after" would be quite late. The PO had mine timed at 12 deg. before and I have it now at the stock 4 deg. after. I could get it to idle just fine either way. 21 deg. before seems like a little more advance than you need but it should still idle.

Personally, I suspect the carbs. I would look at the fuel filter and check for leaks as suggested above. I would also see if I could adjust the idle speed screws to get the engine to idle at any reasonable speed (700 to 1500 rpm).

Once you can get some sort of idle, you can work from there - changing the timing, adjusting the mixture, etc. Changing the timing or mixture will alter the idle speed and you'll have to go back and change the carbs' idle speed screws again.

If the vac. unit hits, then you probably have the distributor indexed over a spot or two. That's not a big deal and the only problem with doing that is that the vac. unit hits. There was a long discussion about how to change this in an earlier thread:

https://www.britishcarforum.com/bcforum/ubbthreads.php/ubb/showflat/Number/216494/page/0/fpart/5

Bryan
 
Timing: The harmonic balancer may have shifted. It seems that the unit is two pieces pressed together. The part with the timing marks can rotate and be several degrees aft or forward of where they should be. The only fix is to replace the balancer with a known good one or new.

Idle: I would follow the recommendations above closely. also check your compression with a good gauge. You could have a very low cylinder. Which could be a burnt or leaking valve or several valves.

Good luck.
1972 TR6
/bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Even after it is warmed up, if I pull up to a stop light I have to either rev the engine or pull out the choke to keep it from stalling. [/QUOTE]

That statement has lean condition caused by vacuum leak written all over it.

Back to basics. Get a can of spray carb cleaner and start spraying around the intake and all hoses while running to see when/if the idle goes up.
 
Ok, so just start spraying all around the carbs and all the rubber hoses that lead to them? That seems like an easy enough start. I will pick some up in the morning and see what I can figure out. As far as the question above about where I am at with my timing. I believe I am at 21 after at approximately 1200 rpm. After I check for vacuum leaks, can someone help me try and get make sure the timing isn't an issue before I break open the carbs. Thanks for the help. I will let you know what I find out tomorrow
 
21 degrees After Top Dead center is not right, you need to bring number 1 piston to the top of the bore on the compression stroke, both valves closed and see where your timing mark on the harmonic balancer is, if its not close to zero you will have to either replace or make new marks on it with a white paint marker
 
As Hondo said, 21 deg. after TDC is not right (but may not be the main cause of your idle problem). Take out the number 1 plug, put the car in 4th gear and roll the car until you see the piston come to the top of the stroke. Without pulling the valve cover, I don't think you'll know if the valves are closed or not. So just look at the crank. If the marks are nowhere to be seen, then the valves are probably open (you're at TDC of the exhaust stroke). So move the car more and now when the piston gets to the top again, you should be at the top of the compression stroke. Now look for the timing marks.

It will be hard to tell exactly when the piston gets to the top of the stroke because it barely moves around TDC. But if the marks show that you are close to TDC, then you are probably OK. If you want to be exact, you'll need a dial indicator with a long extention to put in the spark plug hole so you can figure out exactly where TDC is.

Bryan
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] If the marks are nowhere to be seen, then the valves are probably open (you're at TDC of the exhaust stroke). [/QUOTE]

Won't matter whether intake or exhaust stroke in relation to the timing marks: #1 TDC is in the same place on every crank rotation. /bcforum/images/%%GRAEMLIN_URL%%/smirk.gif
 
D'oh! /bcforum/images/%%GRAEMLIN_URL%%/blush.gif

Bryan
 
Here we go. A correction to my previous posts. I am at 20 before, not after. I am not sure if that will make much difference. After spraying carb and choke cleaner I did notice the RPM's go up a little when I sprayed it at the large 1/2" rubber tube that attaches to the front of the rear carb. It is the tube that attaches to the valve cover and also goes down to the carbon canister (I think that is what that is?) after T'ing and connecting to the front carb. Can I just put a metal hose clamp on this where it meets the carb to try and stop the leak, or is there some other way that is preferred? I was not able to find any other leaks, but I will take care of this one and check again.

Also, I was able to find TDC or at least close to it and I was pretty much dead on the 0 line on the harmonic balancer. So, I do not think it has slipped or that I will need to mark new lines. When at TDC, I took off the top of the distributor and the rotor was pointing to the #1 plug wire, which was at approximately at 7 o'clock. I will attempt to reread the link given to me by BryanC above and see if I can digest what it is saying to try and move the distributor around so I can get it over to 4 after.

Thanks for all the help thus far!
 
I think you should be able to get the car to idle with the timing at 20 deg. before TDC. There must be another issue. I gather that it idles well enough to check the timing in the garage. When is the idle a problem? Are you sure you don't just need to adjust the idle speed on the carbs?

A couple of other things about timing... I think you said you had it idling at a relatively high speed (say 1200 rpm). The 4 deg. ATDC is the timing at around 750 rpm. The timing will advance as the engine speed goes up. So if you measure 20 deg. BTDC at 1200 rpm, that corresponds to a later timing at 750 rpm (I don't know what - maybe 12 or 16 deg. BTDC). My car idled just fine at 12 deg. BTDC at 750 rpm.

Also remember that as you move the timing toward something like 4 deg. after, the idle speed will drop. So, you'll have to adjust the idle speed screws on the carbs as you go. If you are already having trouble with the idle, then it may seem like things are getting worse as you retard the timing. Adjusting the screws to bring the idle speed back up should allow you to return the idle speed to whatever you want.

Bryan
 
Bryan is correct. You should start at 12 degrees and probably at 850-950RPM. If you can get is smoothly idling at a lower RPM that is fine also. 20 degrees BTDC is a bit far for a stock distributor and car. You may want to bump it from 12 to 14 to 16 to see how it runs after you get the other issues resolved.

What condition are your points in and what is the gap setting on those?

Try to eliminate any variations in idle caused by vacuum leaks and move forward from there.

So here it is:

1. Correct any vacuum leaks
2. Check points and settings
3. Reset timing and idle
 
You might want to check a couple other easy items as well.

Spark plug wires / cap connection tight?
Rotor in good shape?
Distributor cap in good shape?
Air filter in good shape?
Fuel filter in good shape?
Dash pot oil correct weight and topped off?

I learned the hard way to always make sure you have the little/cheap things base lined before starting to dig in. <grin>

One other quick thing, if memory serves the Stromberg carb membranes do not like carb cleaner (makes them brittle and then they tear) so you might be a bit careful about how aggressively you spray the carb cleaner into the carbs.
 
On my vacuum leak, I am just going to replace the 6 inch section of tubing and see if that fixes the leak. I figure that is probably the easiest way. Anything I need to do other than just cut a new piece of tubing and put it on?

I am not running points, I have a pertronix setup.

Everything seems to be in pretty good shape. I will take a look at everything once I get the tubing replaced. If that is the right thing to do.
 
I replaced the tubing and I no longer have a leak. I then adjusted the idle and I was able to get to idle without the choke at approx 1100 RPM. I cannot get it much lower before it bogs down and then stalls. I had the neighbor who I just found out is a mechanic come look at it and he verified there was not a vacuum leak and played around a little bit but was not able to get the idle down any lower. We did notice I need a new choke cable as the cable that goes to the rear carb is not moving. I do not believe this has anything to do with the idle as I am having problems getting it to lower and this cable is stuck in the off position. It also isn't purring. It is kind bogging up and down a few hundred rpm going between 1050 and 1300. Is it possible to hold a smooth idle at like 850? Any further ideas, or should I just be happy where it is?
 
That six cylinder engine should run a smooth as silk at 850 rpm's. Did you take the tops of the carbs off and check for a ruptured diaphragm as RonMacPherson had suggested in an earlier post. You have to look very carefully, as sometimes the crack is only visible when you start stretching the rubber around.
 
Well, my car idles nicely between about 700 and 800 rpm so it is possible. You don't have some sort of a wild, race-only cam do you? My next though would be that the mixture is wrong - perhaps too lean. The mixture is fairly easy to change if you have the special tool (see Moss, TRF, etc.). I have used the Gunson Color Tune (also from the usual sources) to set the mixture on my cars with some success.

I'm new to the ZS carbs so others may have better ideas of what else can go wrong with them.

Bryan
 
I have not taken the tops off the carbs yet, mainly because I am a little intimidated and I am not quite sure what I am not sure where to start. I guess I just need to find some instructions and dive in. I do recall the PO did tell me he put a sportier cam in it, but I guess I don't really know what that means or what it effects.

I do have the ZS balancer and the tool, however all of my plugs are gapped to .025 inches and have a nice cappachino color.


I guess I will tear into the top of the carbs and look for tears. Can I remove the tops without comepletly taking the carbs off the car?

Thanks,
 
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