Bad running, help please

[MrMCI]

Hi All,

It has been a good few years since I last posted as my TVR has been glorious then laid up for a few years as my children grew up to the point where I can take them out

This year I've got my Griff 500 out of hibernation with a full fluid change. Started up first time, ran beautifully, went for a 30 mile drive and when I got home and parked up it struggled to restart, initially it just cranked without firing and then at second attempt started on the first turn.

The next time I came to drive it, it started and ran beautifully, until it got hot. At which point the revs started fluctuating at tickover, and I think the fans cut in more soon than usual. Whilst driving I started getting really rough running below 3k rpm (seemed better at higher revs) before it cut out completely and struggled to restart.

I took it out for another test drive yesterday and again, started fine, ran fine, till it got hot and the main fans kicked in (again sooner then I'd have expected) when it started getting lumpy and ultimately cut out. I managed to limp 2miles home with it really struggling, with backfires, cutting out and revving to 1.5krpm at tickover or stalling and struggling to restart.

Between the last two drives I've cleaned the stepper motor which seemed clean. I've also changed the coil as I had a spare. Coolant level looks fine with no air locks as the heater is working.

Any ideas of what to check next and how to do it?

Thanks in advance

Mark

[Loubaruch]

You need to assess the problem logically, randomly changing items can proove lucky but more than often can lead you to chase your tail.
Get hold of a Roverguage interface lead and run Roverguage on a laptop, there are many experts on here will then be able to diagnose the problem from the Roverguage data.

[NicBowman]

I hate to say this, but I get some outside help sometimes! It hasn’t cost you much over the last years. Use the unspent 'TVR fund' (we all have one, surely?).

Sometimes these issues need a person practised on the diagnostics. Can save a lot of frustration.

Best of luck

Nic

Edited by NicBowman on Tuesday 23 August 08:12

[Polly Grigora]

Do you have access to a multimeter to carry out a voltage check on a few circuits when the problem occurs?

[blaze_away]

I have a Chim 4.6 running the standard 14CUX.

Had running issues in the past and over the last few years I have taken a close look at understanding and interpreting RoverGauge data. Just yesterday I put out a post about it on chimaera ph forum.

If you can run rovergauge ? I will look at the data for you

[MrMCI]

Thanks for the help and support chaps,

I don't have a rovergauge so I guess I'll have to take it somewhere. I'm ok with older cars but without being able to diagnose the ECU I feel blind. Someone has suggested trying to disconnect the MAF to see if that's at fault so I'll give that a go when the rain stops.

Mark

[Loubaruch]

Roverguage is free software you just need to buy an interface cable to connect from the ECU socket to a laptop.

Google "Roverguage" to find everything. The best £35 you will spend on your TVR!

[MrMCI]

Ok thanks, sounds like it's worth a go. I've never had much luck with ECU diagnostics on any car. Can anyone tell me where the hotwire terminal should be so that I can check it's the right connection.

[blaze_away]

MrMCI said:

Ok thanks, sounds like it's worth a go. I've never had much luck with ECU diagnostics on any car. Can anyone tell me where the hotwire terminal should be so that I can check it's the right connection.

In footwell with the ECU, 3 PIN Plug sort of rounded triangular shape

[swisstoni]

Just a thought; is the fuel fresh and good stuff?

[MrMCI]

Hi, yes filled at least 50% of the tank 2 months ago with Tesco super. It's running absolutely fine till it warms up, then it goes bananas.

[blitzracing]

Possibly flooding. Drop a plug out and see if its sooted while you get RoverGauge. Couple of odd things to check meanwhile, make sure the fuel temp and water temp connectors are not swapped and check the inlet pipe has not collapsed.



https://www.ebay.co.uk/itm/314090482320?hash=item4...

[swisstoni]

I’m not terribly mechanical, but on a non-TVR of mine I had a heck of a job working out why it ran funny when warm.

Turned out to be a faulty coil. It basically failed to do what a coil is supposed to do when it heated up. I didn’t even know they did heat up.

Replacement fixed it.

[Aussie John]

I would be tempted to change the ign. amplifier, if not the problem then you have a good spare, PS is that Quinny's old car?

[Steve_D]

MrMCI said:

.............. It's running absolutely fine till it warms up, then it goes bananas.

Typical MO for failing ignition amp.
My old Rangie would take me 'almost' to work and break down 100yds from the gate. When I went back to it after work it would usually get me home but not always.

Steve

[dantvrgriff]

I have had similar problems for years. After changing loads of parts without fix, it was just a loose electric connector at the generator.

[MrMCI]

Ok thanks, sounds like ignition amplifier is worth a try. Someone off the forum suggested that it could be the mass airflow sensor and that I could disconnected it to test, that is on the list of things to do but don't really want to breakdown 5miles form home if it doesn't fix it.

Aussie John, yes it is Quinny's old car, I've had it 11 years now and always loved it. I bumped into him having just come off track at Classic Le Mans 4 years ago.

[Aussie John]

Hi Mark, I spoke to Quinny yesterday and he said the Griff is out of warranty so don't bother ringing [ chuckle ] Didn't you have a Lotus, maybe a Europa?

[MrMCI]

I can now report back, my car has been to Joolz at Kits and Classics (who comes highly recommended). It turns out that I had two separate issues which combined to give the odd symptoms.
1) knackered rotor arm which was breaking down once it got hot
2) interdependence between the blower motor and the speed sensor circuit, so the car thought it was moving when it was stationary, throwing out the tickover.

The result was it is fixed and it has a power run while it was there. 317bhp and 340ft/lb, with a beautiful power and torque curve, all the way up to 6k rpm (and some say 500s don't like to rev). Not a bad result and a credit to Andy Quinn who built it 12or so years ago. Nice work Quinny!!

[Belle427]

Great result, is the engine standard as it left the factory?