cutting out when coasting to a stop?

[jesfirth]

griff 500 (sorry but you guys are much better at responding) preserp.

question 1. It used to very occasionally stall when the engine was cold for the first mile of a journey but was ok when warm. died at each stop last weekend which was a PITA.

dirty stepper motor?

BTW the speedo is connected but does not work because the trigger wheel on the prop shaft was removed. It worked fine after removal though for 6 months.

Question 2. on sunday when hot it refused to start. fuel pump primed - turn key the extra bit nothing at all. it bump started fine as has started just fine ever since. Dreaded hot start? - except it has no immobilser - stumped on that one.

[QBee]

Question 1. First thought like you is that the stepper is not coming in quick enough to catch the falling idle. Mine did that when the original stepper became temp sensitive. Not saying yours is, but the symptoms are those of an incorrectly working stepper. If you are near any PH Chim owner, just borrow theirs and swap em over to test it. If you live near Newark, borrow mine.

Question 2. Could be several things, but if not immobiliser, then it could be starter wiring related - either a poor earth or antiquated knackered live lead. The live lead should have been thicker, and as they get old and crusty the resistance gets higher and higher.
Otherwise it could just be the beginning of the end for your battery,

I don't think the two issues are related

[FlipFlopGriff]

Jes,
Try another ECU first.
Then look at the earth strap on the engine.
Slow response Griff owner!!
FFG

[simonwedge]

I've had this as well when the wires from my speedo sensor became disconneted. If it's like mine it won't bump either - you have to turn the ignition off and then restart it.

I found out that that, as well as running the speedo itself, the speedo sensor also sends a signal to the ECU which helps to govern the idle control. Wires reconnected and idle issues solved - simples!

Can't comment on why it has worked OK for 6 months though!..

[blueg33]

Check airflow meter multi plug is properly seated. I had similar symptoms in the G33 (same engine) after exhaust manifolds were replaced. The airflow meter plug had been removed, and had not been seated properly when replaced.

Edited by blueg33 on Thursday 9th June 21:34

[TV8]

If you are still running 14cux then try a spare lucas AFM.

[jesfirth]

All helpful ideas. Thanks chaps. Replicating the problem is the challenge.

BTW. It's on an aftermarket larger AFM and mark adams chip rolling road tuned at TVR power.

[ChimpOnGas]

jesfirth said:

griff 500 (sorry but you guys are much better at responding) preserp.

question 1. It used to very occasionally stall when the engine was cold for the first mile of a journey but was ok when warm. died at each stop last weekend which was a PITA.

dirty stepper motor?

BTW the speedo is connected but does not work because the trigger wheel on the prop shaft was removed. It worked fine after removal though for 6 months.

The 14CUX ECU needs an input from the speedo sensor to work out its idling strategy, if its not present it will definitely cause idling and stalling problems.

Misguided attempts to solve the problem like jacking up your base idle, disconnecting the stepper motor or just hoping cleaning the stepper motor will help are not the answer.

You need to reinstate your road speed sensor/trigger wheel to solve the problem properly

jesfirth said:

Question 2. on sunday when hot it refused to start. fuel pump primed - turn key the extra bit nothing at all. it bump started fine as has started just fine ever since. Dreaded hot start? - except it has no immobilser - stumped on that one.

You have an amp drop on your starter circuit, the reason it happened when hot is because resistance in any electrical circuit increases with heat, the biggest amp drop typically takes place where the circuit passes through the immobiliser but if you don't have an immobiliser the problem can only be in whatever wiring is left on the starter solenoid circuit.

If you take a run of suitable gauge cable from the sprung start position of your ignition switch direct to the starter solenoid you should find the issue will disappear.

When TVR designed the loom for Chimaera's & Griffs they decided they new better than every other car maker and qualified auto-electrician and chose not to fit a relay on the starter circuit so a better solution would be to fit just such a relay. Using a relay ensures the starter solenoid receives a direct feed from your battery while your ignition switch is merely used for the light duty of energising the low amp switching coil in your new relay.

For safety always be sure to include a fuse in any new circuit you create

[andy43]

As above, the ecu needs that road speed signal. It'll hold above idle until car stops, then drop it to idle. Also worth a read - http://ecumate.com/docs/Ecumate%20inst.pdf I just entered the 21st century and got a used ecumate off ebay - it shows what the road speed sensor is doing, I assume rovergauge would show the same thing.

[taylormj4]

ChimpOnGas said:

You have an amp drop on your starter circuit, the reason it happened when hot is because resistance in any electrical circuit increases with heat, the biggest amp drop typically takes place where the circuit passes through the immobiliser but if you don't have an immobiliser the problem can only be in whatever wiring is left on the starter solenoid circuit.

If you take a run of suitable gauge cable from the sprung start position of your ignition switch direct to the starter solenoid you should find the issue will disappear.

For safety always be sure to include a fuse in any new circuit you create

Not wishing to be picky ChimponGas (I know you know your stuff) but you don't actually get amp drop around a circuit (if that's what you meant - apologies if you didn't); amps are always constant all the way around a circuit from start to finish. What you do get is voltage drop. So a bad connection or any other high resistance will cause voltage drop such that at the terminals of the starter or the solenoid, there is lower voltage than there should be.

The amps flowing in any circuit are the source voltage divided by the total circuit resistance.

Using a voltmeter, you should be able to trace around the circuit (leaving the -ve lead on earth or the battery) and see where volt drop is occuring and then tackle that, whether it is a bad connection or a fractured lead.

To be fair to TVR, the circuit that they provided (immobiliser wiring error and fusing aside) was up to the job for the first 10 years or so but what appears to be happening is that as the starter ages, the solenoid seems to need more and more current to actually operate, probably as it gets less lubricated. Eventually, the solenoid requirements go beyond what the original circuit can deliver. The choices then would be replace / overhaul the starter such that the original circuit is again sufficient or beef up the circuit as ChimonGas has explained in detail in several posts to accommodate the aging starter.

Top advice on adding a fuse to any circuit. The fuse should always be rated at a lower current than the weakest part of the circuit (usually the wiring) so that it is protected from catching fire.

[x works]

Yes as above .. You need a speedo signal , when you have , disconnect then re connect your eng ecu to clear any faults .
Should be all good then

[ChimpOnGas]

taylormj4 said:

Not wishing to be picky ChimponGas (I know you know your stuff) but you don't actually get amp drop around a circuit (if that's what you meant - apologies if you didn't); amps are always constant all the way around a circuit from start to finish. What you do get is voltage drop. So a bad connection or any other high resistance will cause voltage drop such that at the terminals of the starter or the solenoid, there is lower voltage than there should be.

The amps flowing in any circuit are the source voltage divided by the total circuit resistance.

Using a voltmeter, you should be able to trace around the circuit (leaving the -ve lead on earth or the battery) and see where volt drop is occuring and then tackle that, whether it is a bad connection or a fractured lead.

To be fair to TVR, the circuit that they provided (immobiliser wiring error and fusing aside) was up to the job for the first 10 years or so but what appears to be happening is that as the starter ages, the solenoid seems to need more and more current to actually operate, probably as it gets less lubricated. Eventually, the solenoid requirements go beyond what the original circuit can deliver. The choices then would be replace / overhaul the starter such that the original circuit is again sufficient or beef up the circuit as ChimonGas has explained in detail in several posts to accommodate the aging starter.

Top advice on adding a fuse to any circuit. The fuse should always be rated at a lower current than the weakest part of the circuit (usually the wiring) so that it is protected from catching fire.

Spot on

You can read more here to support what I've been saying for a years, look down the page for the section titled.... The car fails to start when the engine is hot (TVR's)

http://www.abacuscaralarms.co.uk/tvr-alarms.html

Abacus Alarms are Meta trained auto security professionals who clearly understand the true source of problem and the proper way to fix it, here's what the experts say....



The M36T2 immobiliser is a two circuit Thatcham approved immobiliser, it is manufactured with very high quality components to a very high standard & as such this is one of the most reliable immobilisers manufactured today, many of these systems are still working perfectly on vehicles which are well over 15 years age.

Problems arise because TVR have wired the immobiliser circuits the wrong way around.

The M36 has two immobiliser circuits, circuit 1 can handle currents of up to 10 Amps & should be wired to the fuel pump or ignition circuit, circuit 2 is rated at 25 Amps & is designed to be connected to the starter motor circuit.

TVR have wired these circuits the wrong way round, the starter goes through the 10 amp while the fuel/ignition goes through the 25 amp circuit. All being well there are no problems even though the two relays are wired the wrong way around.

Problems arise when the starter solenoid begins to wear, in so doing it demands more & more power to function, when the current flow to the starter gets passed the 10 Amp limit of circuit 1 problems start. This situation gets worse when when the engine is hot which in turn makes the starter solenoid hot causing it to demand more power.

This is known as the hot start problem, eventually the starter circuit will burn out causing total failure of the starter.

Adding an extra 'hot start' relay to this circuit is not a permanent fix as the starter will still demand more power which could eventually burn out the ignition switch or associated wiring leading to the failure of the starter itself.

Before this happens we recommend to have the starter inspected & have it repaired or replaced if found faulty.

All replacement TVR adapted M36T2 immobilisers will now be sent out with the immobiliser circuits switched to match the TVR wiring, this will now match the higher rated relay to the starter circuit of the TVR, this should cut down on the hot start issue

chimpongas said:

I've been trying to explain the above your years (just probably not as elegantly), doubters can now see it for themselves on a website created by a professional Meta agent who clearly knows his stuff. Abacus Alarms repeats my message that the "Hot Start Kit" sold by David Beer of ModWise is not a proper and complete solution to the problem, and I personally have felt for years it's very misleading to sell it as a cure!

David Beer's website says this...

By putting back into the starter solenoid circuit a relay to supply the power, the dreaded hot start is cured.

This is clearly not the case as supported by the information on the Abacus Alarms website, I have no connection with Abacus Alarms and actually only found what they say about the problem very recently, however it is exactly what I've been trying to tell people for years.

I just want to protect my fellow TVR enthusiasts from buying something sold as a "CURE" when it clearly isn't, breaking down far from home with the same problem when you've been sold a so called "CURE" could be really inconvenient!

Edited by ChimpOnGas on Sunday 12th June 10:08

[jesfirth]

Fixed the starter. Loose connection to the solenoid wire. Access to fit a new terminal is horrible. Just like painting the hall through the front door letterbox.

Speedo now works the sensor just needed a clean and adjutant. Hopefully thats sorted the stalling. Can't road test at the moment busy plumbing in a new fire extinguisher system.

[Englishman]

Well done, yes, electrical issues with TVR’s are often easy to fix.

From a personal experience perspective I would clean the stepper motor anyway as these do collect carbon over time and cause stalling issues when coasting to a stop. Usually no need to buy a new one, although of course that will have the same effect as cleaning.

[Pedant mode on] It does annoy me how some people talk about amps. An Ampere (abbreviated to amp) is a measure of electric current, in the same way that a metre is a measure of length. As someone else said, in any circuit the current flowing is constant unless something in the circuit changes. [Pedant mode off]

I have no connection with Mr Beer, but do understand and applaud his work-around to the hot-start problem though. In effect what his solution does is to remove the current limit on the incorrectly wired 10 amp rated immobiliser circuit. This has the same effect as rewiring the immobiliser correctly.

In my experience (30 years of RV8 engines in TVR’s), the starter motors do draw more current as they get older, but rarely (never in my personal experience) to the point of drawing enough current to cause issues elsewhere in the starting circuit. If they do, this issue would apply whatever mods had been made.

[jesfirth]

Fixed the starter. Loose connection to the solenoid wire. Access to fit a new terminal is horrible. Just like painting the hall through the front door letterbox.

Speedo now works the sensor just needed a clean and adjutant. Hopefully thats sorted the stalling. Can't road test at the moment busy plumbing in a new fire extinguisher system.

[ou sont les biscuits]

Englishman said:

I have no connection with Mr Beer, but do understand and applaud his work-around to the hot-start problem though. In effect what his solution does is to remove the current limit on the incorrectly wired 10 amp rated immobiliser circuit. This has the same effect as rewiring the immobiliser correctly.

The only fly in the ointment though is that by the time the hot start issue manifests itself, the 10A relay in the immobiliser has already been damaged, and no amount of workarounds (other than either replacing or bypassing the immobiliser) are going to fix that.

A new correctly wired M36T2 is only a hundred quid or so, so replacement isn't all that expensive. IMHO of course. Getting at it is another issue though