Unrequested RPM increase

[scruggs]

Had to move the Tuscan today as it was blocking in the wife's Chim and as it will be off road for a while (see gear lever thread elsewhere) it needed to be repositioned on the driveway. (I found first gear by shoving the stick in a wiggling it carefully). Back to topic, the car had not been started for a few weeks and lives outside under a full cover. Turned it over on the key and after a few compressions it fires up and settles into an 800 rpm tick over. I give it a couple of minutes then touch the accelerator and vroooom! The rpm went through the roof. I didn't see exactly what rpm it made but somewhere north of 4,000 sounds about right. I immediately turned it off on the key. Second start up and its back to 800 but the throttle is over reacting, a merest tickle on the pedal has it up to 2,000 rpm for a couple of seconds then it falls back again. A slightly bigger tickle and the rpm goes stratospheric again!

[V8 GRF]

If that was happening to my Griffith I'd try resetting the ECU but I don't know if that's an option on the Tuscan?

[m4tti]

Revs increase with fuel and air.. so the butterflies have to be opening up a fair way and that position read by the pots.

Have you taken the bonnet off and made sure there isnt some issue with the throttle linkage/butterflies opening to far or sticking.

[scruggs]

I haven't had chance to investigate it yet but it was working just fine when it was last on the road a few weeks back. Re-setting the ECU as suggested might be the first port of call, if I knew where it was located.

The only thing that has been disturbed since it was last used is that the central console has been lifted off to gain access to the gear lever gubbings.

Also the drivers side carpet was soaked despite being under a full cover, which is also odd.

[s6boy]

Throttle cable fraying and catching or if you've been moving carpet around possibly getting caught/fowling under the pedal.

As suggested try taking the bonnet off and increase the revs manually. If they drop off as normal then it's pointing towards the cable or carpet.

[scruggs]

Ok thanks will check for that as well. My only doubt is that I hardly pressed the pedal at all, we are talking about light foot pressure resting on the pedal so cable travel would have been minimal.

[ratboiler]

You don't seem to be having much luck, I hope the situation improves for you, good luck.

[scruggs]

Well I paid under the going rate for it 18 months ago knowing it had been little used for a few years and that there were a couple of cosmetic jobs to be done. But it has diverted my bank account into a new slave cylinder, 4 new shocks, 2 wishbones and a 12k service instead so the cosmetics have yet to be attacked (stone chips, carpets etc). Luckily its not my daily driver so it can wait its turn at fleecing me more.

Ah the joys of TVR ownership, and we have two!

[nawarne]

V8 GRF said:

If that was happening to my Griffith I'd try resetting the ECU but I don't know if that's an option on the Tuscan?

The MBE ecu can suffer from poor contact on the 3 multi-pin plugs providing in/out data.

A mate was 'sorting' a Tamora for a work colleague. The car had developed a misfire. The 3 plugs were 'lifted' and contact cleaner used before re-making the connections. It cured the problem.
Nick

[m4tti]

Sounds most likely to be mechanical though, as the air fuel balance is right letting it rev up. Has the return spring some how lost tension.