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Lumpy running/sooty plugs


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Hi all

I am checking out lumpy running and a vague miss when taking up the revs,the car had this problem when purchased last year,(one of the many jobs to do),I am tackling this job with a mechanic friend of mine with little 1972 tr6 experience.The plugs seem to be new NGK BP6 ES But all but 1 and 2 are really sooty! and the points are new.Will be using a dwell angle meter and vacuum gauge and fitting champion N9Y plugs and renewing points,just in case it’s something simple,as I know even less than my friend I was wondering if there were any pointers from the eternal fountain of friendly and patient advice from this forum 

regards nige.   stay safe guys nearly there 

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Familiar story. I’m still tracking all my fuelling gremlins down. 
 

Best bang for buck for me was making sure that the throttle butterflies are balanced and opening a)fully and b) symmetrically -the CR throttle control can get loose so 5/6 don’t ever open properly and run rich. There are replacement kits available. 
 

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5 hours ago, nigelcurry said:

Hi all

I am checking out lumpy running and a vague miss when taking up the revs,the car had this problem when purchased last year,(one of the many jobs to do),I am tackling this job with a mechanic friend of mine with little 1972 tr6 experience.The plugs seem to be new NGK BP6 ES But all but 1 and 2 are really sooty! and the points are new.Will be using a dwell angle meter and vacuum gauge and fitting champion N9Y plugs and renewing points,just in case it’s something simple,as I know even less than my friend I was wondering if there were any pointers from the eternal fountain of friendly and patient advice from this forum 

regards nige.   stay safe guys nearly there 

Here are some of the key pointers from my own 45 years of TR experience!

1) compression check hot. I would expect 170psi approx. Butterflies must be fully open.

2) Use grade 5 NGK plugs. That usually sorts out cylinder 5 & 6

3) Rev engine up suddenly when hot to see if there is any signs of black smoke from the exhaust, If there is this is usually down to the M/U needs a rebuild or low compression.

4) Do tongue test on M/U to see if it holds vacuum. This affects mixture.

5) Check for leaks on manifold and are manifold nuts tight or any nuts and clamps are missing. Sometimes they have a habit of falling out, stud and all.

6) Check ignition timing running.

7 Check condenser and rotor arm. If Rotor arm has a brass rivet and is black in colour bin it and get a red colour one. The black ones unless they were OE are a major source of aggro. They fail any where, any time.

Bruce.

 

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I use a NGK5ES in 5&6 & NGK6ES in 1-2-3-4.

Is the car a PI or carburettor? 

 

If it is a PI then:-

Because the PI runs rich at tickover there is a method to check the plug condition. Get the engine hot, and then run the engine at 2,000 revs for a minute'ish then immediately  kill the ignition. Now check the plugs. If the engine is allowed to tick over, especially when cold they will always come out sooty.

Cylinder 5&6 at the bulkhead end of the engine are the usual culprits for being sooty. 1&2 at the radiator end are usually ok I would suspect butterfly sync issues.

If the car is a little lumpy as you take up the drive when pulling away it is often a butterfly synchronisation issue not spark plugs. If the butterflies are incorrect then the engine will happily tick over on a couple or more cylinders the remaining cylinders getting little air and running even richer and sootier at tick over.

A couple of quick tests, screw the slow running screw right in at tickover, does the engine stall? If not there may be manifold gasket leaks or butterfly sync issues.

Remove the air-box plenum. With the engine ticking over blank off each cylinder's throttle body  one at a time. You will soon see if the engine is ticking over on all six or just on a couple. Butterfly synchronisation issues are only apparent at tick over, once the butterflies open and the car is moving in gear the load on the engine, flywheel etc all smooth out the engine.

If it is the butterfly synchronisation you need the correct tools and plenty of time and patience to get them close to being correct (and asbestos fingers). 

Alan

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2 hours ago, Mike C said:

I had sooty plug problems when driving in traffic, then about 2 years ago I switched to NGK BUR 6ET plugs. They are expensive in Aus, but I've had no plug problems since.

+1

NGK BUR6ET triple electrode plugs (or Bosch WR78) work well in my CP series '6.

Watch out for fake NGK plugs, the problem has been mentioned on this forum before. Green Spark Plug are well thought of and not expensive for NGK:

https://www.gsparkplug.com/catalogsearch/result/?q=BUR6ET

As mentioned above, throttle synchronisation is important for smooth idling and low speed running.

Nigel

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1 hour ago, barkerwilliams said:

I use a NGK5ES in 5&6 & NGK6ES in 1-2-3-4.

Is the car a PI or carburettor? 

 

If it is a PI then:-

Because the PI runs rich at tickover there is a method to check the plug condition. Get the engine hot, and then run the engine at 2,000 revs for a minute'ish then immediately  kill the ignition. Now check the plugs. If the engine is allowed to tick over, especially when cold they will always come out sooty.

Cylinder 5&6 at the bulkhead end of the engine are the usual culprits for being sooty. 1&2 at the radiator end are usually ok I would suspect butterfly sync issues.

If the car is a little lumpy as you take up the drive when pulling away it is often a butterfly synchronisation issue not spark plugs. If the butterflies are incorrect then the engine will happily tick over on a couple or more cylinders the remaining cylinders getting little air and running even richer and sootier at tick over.

A couple of quick tests, screw the slow running screw right in at tick over, does the engine stall? If not there may be manifold gasket leaks or butterfly sync issues.

Remove the air-box plenum. With the engine ticking over blank off each cylinder's throttle body  one at a time. You will soon see if the engine is ticking over on all six or just on a couple. Butterfly synchronisation issues are only apparent at tick over, once the butterflies open and the car is moving in gear the load on the engine, flywheel etc all smooth out the engine.

If it is the butterfly synchronisation you need the correct tools and plenty of time and patience to get them close to being correct (and asbestos fingers). 

Alan

Whilst I agree with you on butterfly synchronisation, but I do not agree that the the synchronisation s/b done at tick over. This is not as per Brown Book or my experience? In my view it cannot be successfully done without some sort of air flow meter, like a Cryton Synchro but there are others now, check and hold revs at 1500 RPM. Adjust the fast idle speed by pulling the cold start cable out of the adjuster with the cam turned to its maximum lift position. turn the adjusting screw  until the engine revs maintain a steady 1500-1800 RPM as per brown book. I have used the Cryton Synchro Check for over 45 years, in its day it was the DB's for tuning twin carbs and the Brown Book also uses it.

Bruce. 

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6 hours ago, Hawk said:

I have had similar problems which were ultimately traced to a combination of 2 things ... a lazy injector and a tiny hole in a vacuum pipe.

If you car is a Pi, plugging a vacuum gauge into the brake booster connection is always a good check of the  inlet system's integrity. Since time immemorial my car needs to achieve 10" Hg at 900 rpm - other engines  may be different but the ball park's in that area. 

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See!! That’s what I mean about this forum.its never failed me with plenty of patience and knowledge.Mike can I show my ignorance and ask what and where would I find the brake booster connection, we will be working our way through all of the points covered Many Many thanks all

regards and stay safe all

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44 minutes ago, nigelcurry said:

See!! That’s what I mean about this forum.its never failed me with plenty of patience and knowledge.Mike can I show my ignorance and ask what and where would I find the brake booster connection, we will be working our way through all of the points covered Many Many thanks all

regards and stay safe all

It's the rubber hose connected to the brake servo (the drum behind the brake master cylinder). I just disconnect the hose to it (the car is stationary for this test) and plug in a vacuum gauge using a conical adapter.

You should get a stable vacuum reading of at least 10 inches of mercury with the engine idling. Any less and you've probably got a leak somewhere in your inlet system.

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Bruce,

At no time have I every suggested that any sort of PI adjustment should be done at tickover without tools.

What I do suggest, for diagnostic purposes, as per my experience of a couple of PI's is that with the TB plenum removed blank off each TB one at a time.

My experience is that if the butterflies are shut completely, as they should be at tick over and the engine running only on the air via the slow running adjustment screw, then blanking off each TB intake will make no discernible change to the tickover, nor will the blanking object used, whether plate, palm, or cloth, be slammed into the TB as the engine draws in air, and all six should have the same negligible induction at tickover through the TB inlet.

It is a very quick and easy test and  has enabled me to determine in a minute or two that the butterflies are not synchronised correctly.

The TR6 PI's  in my experience are perfectly capable of ticking over on two cylinders with reasonable airflow and four air-starved and gaspingly fuel-rich, a setup which leads to a jerky pulling away as the rich cylinders gasp and splutter to clear themselves and contribute to the party

That of course is only diagnosis and the work needed to correctly set up the butterflies, involving worn shafts, twisted butterfly shafts, bad adjustment could take up several volumes, and I personally do not believe that is is possible to ever get 100% correct. Yes one can get close'ish but there is always just that little something  that stops anyone getting to 100%. Presumably that is why some owners have gone to a single throttle body, electronics, or whatever seeking the holy grail.

...and of course that is before we address the low-revs pulling away differences of cam-shaft selection.

Alan

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