Sticky needle and throttle!.

[MPETT]

Hey chaps. Having a few niggles I wondered if you could help with?

The speedo needle has been working fine, but after an extended drive, it stuck at 70mph. The digital reading was correct. Then the needle kept moving higher and higher all the way to 200mph. Seems like needle is slipping on the shaft!?

The other issue is throttle is sticking open a bit. If I come off the throttle fast the engine revs settle down quickly, if I'm gentle and come off the throttle to change gear, the revs rise a little and then when the next gear is engaged, it slows again. I've checked the linkage to the throttles, and greased everything. Nothing feels stiff. Maybe a harder spring on the throttle cable below the throttle bodies? Any ideas welcome.

Re shocks, anyone using Protech and can recommend settings? I'm running rear and front at 9 clicks clockwise.
Cheers,
Martin

[MPETT]

Think I sorted the throttle. The spacers on the pivot shaft between the throttle and brake pedals are quite tight and didn't spin freely around the shaft. I therefore cleaned spacers/bushes with wd40 and a toothbrush. I then removed the throttle pedal linkage arm and gave that a clean too. I also remembered reading somewhere that the throttle cable bracket, at the pedal box can be bent slightly upwards to stop the cable bending and prevent the cable weakening and eventually breaking. I then reassembled with grease and now seems a lot better.

Edited by MPETT on Tuesday 25th February 23:26

Edited by MPETT on Wednesday 26th February 10:46

[Cockey]

I could do with doing that with my pedal box. My throttle behaves exactly like yours when I haven't used the car much .

I just HATE working in the footwell!

[Basti]

Maybe there is a gap between the wormscrew and the needle cog.


Regards, Basti

[nawarne]

Martin - re: the sticky needle.

We were away in January, and on my return - when we had a dry day, took my car out for a drive.
I had a similar issue in that the needle would not "reset" to zero mph when you switched on. The needle seemed to stick below the analogue graduations....consequently there was a 5-10 mph delta between the digital speed read-out and the needle indication.

I removed the instrument cowls and squirted Servisol into the speedo drive. This seems to have cured the problem. I think the worm/pinion drive probably gets stuck if not used for a while? (As Basti's post & photo).
Nick

[MPETT]

Mine's slightly different to yours nick in that it does zero after an ignition off and back on again.

[MPETT]

I had enough of the speedo playing up and took it off to take a close look at the worm drive.

It feels fine and free when you rotate the worm drive to move the needle from 0-200mph, then on the way back down the worm drive become tight for a while, then loosens up again. I think this might be indicate a worn bush? I'm going to try applying some lithium grease and see if that works. I was going to talk to Paul smith about upgrading the chips to provide the enhanced functionality of the later units, so ill ask him about replacement of the rotary jobbie that turns the worm drive.
Alternatively, maybe I could install a digital cluster/dash but I wouldn't know where to stray with all that wiring!

[MPETT]

Re the sticky throttle, I've cleaned up the pedals, linkages and cable but still the problem occurs, just that this time I recognised that it was when the engine temperature got towards the 90s. So, I took a look at the trotted bodies and it appears that the arms are very close to the throttle bodies body. I'm figuring when everything gets hot, the throttles expand and the moving parts start to rub, causing a slowing down of the throttles winding back down, due to friction when the throttle pedal is released.

[cerbera8]

Hi did you manage to fix your throttle issue? My tuscan has a similar problem just when hot and when gently applying throttle to around 2000 revs. Have sprayed all pivots and stuff in pedal box about 3 times with wd40. Also checked cable on pedal side and can see no sign of fraying.

[Milky400]

Could this be temp sensor related? ie sending the incorrect message to the ecu?

[MPETT]

I've done 2 things and it s now gone. One of the throttle arms was rubbing against the throttle body, so bent that out a little, but because if this bending it upset the balance et week the throttle pots, so it had to be reset. Powers think the spindles are worn and they struggled to get the engine running smoothly/perfectly. Needle sorted with some grease. Apparently the worm drive cog is not perfectly true.

[so called]

My throttle was sticking a lot last year so I had new bushes fitted.
Its sticking again this year due to lack of winter use.
I just drove to Germany yesterday/today and it was great. TVR Cruise Control.

[MPETT]

so called said:

My throttle was sticking a lot last year so I had new bushes fitted.
Its sticking again this year due to lack of winter use.
I just drove to Germany yesterday/today and it was great. TVR Cruise Control.

That sounds to me like your arms are catching or something is sticking in the pedal box area. Is it all the time or only when the engine gets hot?

[s6boy]

Might be worth examining the throttle cable to ensure it's not starting to fray. It could be catching when released gently but enough energy in the return springs when released quickly.

Brain block, is that how you spell fray?

[cerbera8]

thanks guys

[twinreal]

Have the same problem with the sticking / slow fallback of the throttle to idle after installing a new set of used bodies.
The throttle cable runs free and the throttle spring has enough tension to press the linkage back to idle position.
All linkages seem to run free but have more or less play. I think this is the problem. Any ideas to fix this in short term ?
On long term i want to get them modded with ball bearings. But for now i want to drive it...

Thanks,
Thomas

[MPETT]

You've probably not had your throttles reset/adapted. The throttle bodies can also leak air via the shafts causing airflow issues. Best would be, if sticking isn't an issue, to balance the pot, then do an adaptive reset and go from there.