Mystery mis-fire around right hand bends

[hannadaimlerv8]

My TR4 has for some months now been mis-firing going around roundabouts and right hand bends at moderate speeds. When it does it I can smell petrol. I can replicate the misfire by pulling out the choke fully when the engine is hot. In a straight line or around left bends no problem whatever the speed. It revs to 6000 with highly tweaked engine no matter how hard I push it until turning right! 
I have checked for electrical shorts and cleaned out float chambers and jets. New alloy tank, electric fuel pump and filter a couple of years ago so no debris in fuel system. I am at a loss what to do next. Help. 

 

[stuart]

Thats ignition failure, somewhere its losing spark due to something moving over on the bends, reason you can smell fuel is because your electric fuel pump is still supplying

Stuart.

[BlueTR3A-5EKT]

2 hours ago, hannadaimlerv8 said:

My TR4 has for some months now been mis-firing going around roundabouts and right hand bends at moderate speeds. When it does it I can smell petrol. I can replicate the misfire by pulling out the choke fully when the engine is hot. In a straight line or around left bends no problem whatever the speed. It revs to 6000 with highly tweaked engine no matter how hard I push it until turning right! 
I have checked for electrical shorts and cleaned out float chambers and jets. New alloy tank, electric fuel pump and filter a couple of years ago so no debris in fuel system. I am at a loss what to do next. Help. 

 

How big is the bunch of keys plugged into the ignition?  
We had a customer come to the garage with exactly that problem of cutting out on sharp turns.   It was the ‘bunch’ of keys.   Think gonk, unicorn, tamagotchi, all existing and old house and car keys, nail file etc.  

The ignition key was attached to that lot and plugged into the ignition switch, it was swinging like a pendulum on sharp turns and turning off the ignition temporarily 

 

We fixed it with a new ignition switch and barrel.   We gave the car back with the new key not fitted to the ‘bunch’  and with instructions to keep separate.

 

 

Jiggle your ignition key when going straight to see if the same problem happens.  Ie intermittent ignition switch.

 

 

 

Cheers

Peter W

 

 

Edited August 9, 2022 by BlueTR3A-5EKT

[hannadaimlerv8]

Thanks guys - Stuart, that does make sense. The fuel system has been working fine since I changed everything a couple of years ago. I have two coils fitted on inner wing. Using either makes no difference to the misfire. Electronic ignition might be playing up but is that likely. 
 

Peter- I only use a single key but that’s a useful tip about the ignition switch. There may be something going on there. Thanks. I will check that out. 

The confusing aspect to it being an electrical issue is that I get the same misfire when pulling out the choke. 

Going around a right hand bend would cause fuel surge from carburettor to engine, enriching the mixture possibly - like using the choke. Would a high float chamber level cause that?

John

[stuart]

46 minutes ago, hannadaimlerv8 said:

Thanks guys - Stuart, that does make sense. The fuel system has been working fine since I changed everything a couple of years ago. I have two coils fitted on inner wing. Using either makes no difference to the misfire. Electronic ignition might be playing up but is that likely. 
 

Peter- I only use a single key but that’s a useful tip about the ignition switch. There may be something going on there. Thanks. I will check that out. 

The confusing aspect to it being an electrical issue is that I get the same misfire when pulling out the choke. 

Going around a right hand bend would cause fuel surge from carburettor to engine, enriching the mixture possibly - like using the choke. Would a high float chamber level cause that?

John

If you get the same misfire when you pull the choke out it may well be in the ignition switch as theyre in that same panel and possibly just the action of pulling it out is cutting the ignition. Or check where the feed for the electronic ignition comes from as some are wired direct from the ignition switch

High float chamber level would cause a problem all the time not just on bends.

Stuart.

Edited August 9, 2022 by stuart

[stillp]

3 hours ago, BlueTR3A-5EKT said:

How big is the bunch of keys plugged into the ignition?  
We had a customer come to the garage with exactly that problem of cutting out on sharp turns.   It was the ‘bunch’ of keys.   Think gonk, unicorn, tamagotchi, all existing and old house and car keys, nail file etc.  

The ignition key was attached to that lot and plugged into the ignition switch, it was swinging like a pendulum on sharp turns and turning off the ignition temporarily 

 

We fixed it with a new ignition switch and barrel.   We gave the car back with the new key not fitted to the ‘bunch’  and with instructions to keep separate.

 

 

Jiggle your ignition key when going straight to see if the same problem happens.  Ie intermittent ignition switch.

 

 

 

Cheers

Peter W

 

 

Great photo Peter! I used to drive a hot Imp in which the ignition key would fall out on a hard LH bend!

Pete

[hannadaimlerv8]

Hi Stuart. That’s interesting about the choke pull and the ignition on the same panel. An obvious possible connection but I hadn’t thought of it! Stripped it down this afternoon. Didn’t find anything untoward but the side bolt was missing which secured the panel housing the ignition switch and choke. It was only held on by the two front screws so there would have been movement when the choke was pulled. I inspected the wiring on the ignition switch with a mirror to see if there were any close tolerances but all ok. 
The Lumenition ignition feed is from an auxiliary fuse box. The live feed to the fuse box is difficult to trace at the moment. Working on it, but don’t think that is causing the problem. Thanks though for opening my mind to potential causes.

John

[Peter Cobbold]

Check fuel is not siphoning out of the overflow tube on one of the float chambers, it might be filling to overflowing only during the bend. Siphoning will give a very lean mixture and mis-fire.

[Motorsport Mickey]

Hi John, picking up on Stuart’s point if you have a tightish electrical connection to the distributor. When the engine leans across to the passenger side with weight transfer on right hand bends it swings back across an amazing amount to the right.
There should be an adjustable torque reaction bar, which fits to the engine front plate across to the chassis, with an adjustable rubber stop on a bolt you can allow to just “snub” against the chassis to help prevent the engine moving.

We had a similar problem on the V8 racer with an annoying right hand bend engine miss that was caused by a too tight power feed to the distributor. When inspected at rest the bayonet was seemingly tightly fitted, but was eased nearly off causing the miss.

Mick Richards

[hannadaimlerv8]

Morning Mick.

As usual I have learned something new from you. I have never come across the torque reaction bar. I have just done some research to discover it was fitted as standard on very early TR4s. Although mine is an early 1962 model it was deleted by then. I think the square engine mounts were introduced to keep the engine secure. I have relatively new ones fitted so the engine shouldn’t be moving much. I will inspect them though to make sure. So far I have not found the bar for sale anywhere. Will definitely fit one by the time I compete again. The cabling for the electronic ignition is plenty loose to allow movement though so don’t think this is the cause. However, your explanation of how much the engine moves made me investigate anything relevant. Where I have fitted an extra coil I had to extend the wiring and there was an exposed area at the join (warning - don’t use insulating tape for such purposes, it becomes detached over time). It just might have been contacting the spare coil when cornering. A long shot and will find out later today when I go out in car. 

Peter - That is interesting about the possible siphoning. I have just double checked the overflow holes for the carburettor bowls and they are clear. I also checked the needle valve operations and they are working perfectly when I blow into the inlet.

All good ideas chaps. Thanks. I had certainly run out of them. 
John

[stuart]

12 minutes ago, hannadaimlerv8 said:

Morning Mick.

As usual I have learned something new from you. I have never come across the torque reaction bar. I have just done some research to discover it was fitted as standard on very early TR4s. Although mine is an early 1962 model it was deleted by then. I think the square engine mounts were introduced to keep the engine secure. I have relatively new ones fitted so the engine shouldn’t be moving much. I will inspect them though to make sure. So far I have not found the bar for sale anywhere. Will definitely fit one by the time I compete again. The cabling for the electronic ignition is plenty loose to allow movement though so don’t think this is the cause. However, your explanation of how much the engine moves made me investigate anything relevant. Where I have fitted an extra coil I had to extend the wiring and there was an exposed area at the join (warning - don’t use insulating tape for such purposes, it becomes detached over time). It just might have been contacting the spare coil when cornering. A long shot and will find out later today when I go out in car. 

Peter - That is interesting about the possible siphoning. I have just double checked the overflow holes for the carburettor bowls and they are clear. I also checked the needle valve operations and they are working perfectly when I blow into the inlet.

All good ideas chaps. Thanks. I had certainly run out of them. 
John

I have a stabiliser bar if you want one John.

Stuart.

[hannadaimlerv8]

Absolutely brilliant Stuart. Many thanks. I will message you with my details so you can let me know cost and postage. 
John

[stuart]

Replied John.

Stuart.

[hannadaimlerv8]

Thanks Stuart.

Sorted.

John

[ianc]

I fitted the Triumph torque reaction bar 650325 (see Plate A, item 38 - not listed by Moss, but offered second-hand by Revington).

However, I decided to provide further restraint of my own design. 

This I described in TR Action 130 (May 1996 - also in Technicalities CD, Section G15-G19).  Will fit only TR4 & TR4A as body of sidescreen cars is too narrow.

Ian Cornish

[hannadaimlerv8]

Thanks Ian. I will dig that article out. I am buying the one that Stuart has. Hopefully my modifications to steering rack mount (re: Mick Richards’ advice on the elimination of bump steer) and chassis strengthening will allow the torque bar to be fitted. It’s going to be a bit busy down that area of the chassis.

John

[andyhall]

10 hours ago, stuart said:

I have a stabiliser bar if you want one John.

Stuart.

So that's what it is! got one and never knew 

Andy

[Motorsport Mickey]

The TR engine is a lump and owners who think updated engine mounts can restrain it…are mistaken.
The part is named “ reaction” bar for a reason. Just as with large trucks who overturn on traffic islands ( more common than you think). It’s not the initial left turn ( to go around the island) that causes the problem, but the reverse lock from left to right ( around the island).  Then the left lock to exit the island that builds up the inertia with the vehicle literally hopping from foot to foot and the truck and load extending the suspension hysteresis ( Google it) which finally exceeds the truck parameters… and over it goes.

The engine if viewed when making sharp direction changes, performs an ungainly “ rumba” rocking from side to side and the squashed engine mounts allowing an ever increasing “ reaction” from left to right which is constrained by a “torque reaction”  bar. ( if fitted).
Of course if you want to gain an advantage when racing you strengthen the front engine plate welding 30mm angle or flat plate to the engine plate ( around the outside) pointing forwards ( painted black to match the engine… nobody notices). Then replace the rubber engine mounts with steel solid diameter mounts profiled to imitate the TR standard mounts and bolt in position onto the frame from underneath and use bolts to screw into the steel mounts through the front engine feet… paint them Matt black, nobody looks or notices.
Such a low tech change, surely fixing the engine in position rather than roaming around the engine compartment ( it is after all a mighty lump) can’t help the handling when on the limit… can it ? 

No, having solid mounts on the front of the engine is not a problem, there is still a rubber mount on the end of the gearbox and the only difference I noted in 2 years with the mod was a zzzz sound/feeling at about 4200 revs where a engine harmonic fed through.

The things you do !

Mick Richards 

 

[Hamish]

Just for interest I did an under bonnet video in competition. It was to see carb action but you can see how you can a firmly mount the engine. 
the camera is fixed to the battery restraining bracket so fix and doesn’t move with the engine. 
it’s at Curborough so a lot of change of direction and possibly  more aggressive than a typical tr road run. 
 

under bonnet starts at 3.12

 

[BlueTR3A-5EKT]

Not an huge amount of movement, but certainly some.

Why is there what looks like water dripping from the heater valve stem Hamish?

Peter W

[Hamish]

9 hours ago, BlueTR3A-5EKT said:

Not an huge amount of movement, but certainly some.

Why is there what looks like water dripping from the heater valve stem Hamish?

Peter W

I cable tied the light too tightly to it. 
it’s ok now. 

[stuart]

Don’t forget there is also these steady brackets for sidescreen cars, four on the engine mounts and the larger two on the gearbox mount, part numbers 106428 for the engine and 107895 for gearbox.

Stuart

[ctc77965o]

I had a left hand bend misfire that worsened to be left hand bends and bumps....it was a bad coil.

[Z320]

Hi John,

what about new ground cables from the engine to the chassis?

Maybe you choke is your only ground cable.

The smell fir petrol could be by accident or a different reason.

Any fuel pump pumps always more than the engine needs,

that‘s why you have float chambers and fload valves.

Ciao, Marco

Edited August 12, 2022 by Z320

[hannadaimlerv8]

Thanks Marco.

I have an excessive amount of heavy duty earth cables from engine to body/chassis.

Hoping to get car out today to see if problem still exists after doing a few things you guys have suggested. 
Still think it is electrical as the misfire is instantaneous as I turn into a roundabout. I think a float chamber problem wouldn’t cause such an instant problem. The smell of fuel is probably unburnt petrol in the exhaust fumes when it misfires. The confusion is why the operation of the choke replicates the problem. I have secured that panel on the dashboard now. A test drive later will see if misfire continues. I will report back. 
John