Throttle body refurb

[Chad speed]

Seems that after eliminating all others the most likely cause of the 2500-3000 rpm hesitation on the Tuscan is worm throttle bodies. Anyone had bronze bushes fitted or any other remedy? How much play is acceptable between body and spindle? is there a leakage test that can be done?
Any help would be great.
Chad

[tail slide]

Have you already had the ECU Diagnostics program run on it?

Anyone experienced with it can tell the degree of leakage from the logged fueling data on each cylinder bank.

Edited by tail slide on Thursday 16th July 20:48

[Chad speed]

Thanks Tail Slide, no I haven't had the diagnostics done but it certainly sounds the way to go before I pull the beastie apart. Is it something I could have a go at myself with the diagnostic lead and software or do you have to a bit of an expert. Anyone any recommendations for this kind of work in the Sussex South East?

[tail slide]

Chad speed said:

Thanks Tail Slide, no I haven't had the diagnostics done but it certainly sounds the way to go before I pull the beastie apart. Is it something I could have a go at myself with the diagnostic lead and software or do you have to a bit of an expert. Anyone any recommendations for this kind of work in the Sussex South East?

You could have a go yourself, it comes with a fairly good 'help' section, but to interpret the large logged fuelling table you'd need some help, some may offer over the phone.

Your experienced local (fairly) is..... http://www.austec.co.uk

Edited by tail slide on Friday 17th July 08:14

[Robertjp]

The long term solution is to whip out the spindle and replace the bushes with bearings, anything more than 1/2 mm will gradually start to cause a few issues. Can also cause poor idle too.

www.Str8six.co.uk is the place to go if you want some who has done this a few times, oxfordshire. Jason is top man who knows what he is doing.

I dare say, the home engineer may be able to attempt to if you have a vertical drilling machine...

Rob

[tail slide]

Agree STR8SIX is top choice - just built me a new 4.2 Six with huge performance gains

[so called]

Jason at Str8Six re-conditioned my throttle bodies and pressed in roller bearings.
Great improvement. Kept its tuning much longer and gave a big reduction in "from under the bonnet" noise.
It was worth every penny of about 600 quid.
Engine sounded great after that job and wish I'd had it done at the same time as the engine rebuild.

[Chad speed]

Thanks for the pointers guys, I have access to a machine shop so may have a go at the roller bearing mod myself on the spare set of throttle bodies I have. I assume shielded as well as sealed bearings are used, anyone know the bearing details?
Think it's also time to purchased a diagnostic lead and software and see what's occurring in the black magic box.
Many thanks again for the help, I'll let you know how I get on - Jason may get the job yet, seemed a nice guy on the phone.

[Chad speed]

Just a quick update. Have pulled the spare throttle body assemblies apart and the bushes seem to be in very good condition apart from one (cylinder 6). The bushes look to be the split oilite type - anyone know a supplier/part number? Could also do with some more felt seals as well.
Robert JP - I assume you meant anything more than 0.05mm would cause problems. 0.5mm, or 0.020" in real money is huge. I'd estimate the worst I have on the spare bodies is about 0.05".
So the current plan is to just clean up the spare set (and replace the bush on Cyl 6) and see how we go. For others who may want to go down the sealed deep grove ball bearing route the size most suitable would seem to be 8mm bore, 16mm housing and 5mm wide, available for about £2.50 each. Machining also fairly straightforward but time consuming none the less (if I were a business I wouldn't want to charge any less than the prices I've seen mentioned).
Chad

[so called]

Mine was an early 2000 Tuscan and realy had over 0.5mm wear.
On the early ones there was no bush between the stainless shaft and the aluminium housing.
So, you can imagine the kind of improvement that I saw.

[Chad speed]

so called said:

Mine was an early 2000 Tuscan and realy had over 0.5mm wear.
On the early ones there was no bush between the stainless shaft and the aluminium housing.
So, you can imagine the kind of improvement that I saw.

Over the years I've encountered this problem on SU carburettors, Amal's, Mikuni's and probably a few others I've forgotten but have never seen 0.5mm (0.020") on a shaft of 6-8mm, and these were all at high mileage. I assume the little split bush was a way of reducing the high wear rate (probably not an oilite bush as I previously assumed). Surprised you were able to get any sort of consistent running with that kind of clearance but now makes me think if the SP6 can run with that kind of air leakage what I've got may actually be quite good! Cheers for the help

[andyoleary]

Racing Green fitted a set of their refurb'd TB sets onto my Tuscan about 5K miles ago. They checked them after 1K miles and the balance of the TB's was still as set originally. Checked again after about 3K miles and, again, the balance was still the same. Costs about £250 for the set + fitting if I recall correctly. No more issues with slight hesitance/lumpy running at around 3Krpm/light-throttle/cruising speed.

Andy