Rough running at light throttle- Update

[DW199]

That's an interesting observation.  The Jenvey TP1 kit included a spacer and cover plate.  Do you fit the spacer between the tps and throttle body or between the tps and cover plate?  I didn't fit the spacer that was supplied with the kit as one hadn't been used originally.  

[ECR]

If it is binding on the end of a throttle shaft the spacer should surely be used to space it away so the spacer must go between the throttle body and the tps...

[DW199]

I don't think it is necessarily that simple.  I have just performed an experiment with the tps that I removed from the car.  I assembled the tps on the bench sandwiched between the cover plate and spacer.  I used some flat washers to spread the load on the spacer and then tightened the whole thing up using a 6cm long 3mm allen key.  At light to moderate tightness, rotation of the tps remained free.  As I increased the tightness, it started binding at the full throttle end of travel.  Increasing tightness more caused stiffness throughout the range of travel similar to what I was feeling when the tps was mounted on the car.

I think what is happening is that the relatively weak cover plate is being bent by the screw heads as they tighten up.  This seems to distort the body of the tps causing the binding.  One way to potentially prevent that from happening would be to assemble the tps with the spacer between the cover plate and body of the potentiometer. This would spread the load better and would hopefully prevent the binding.  There is another experiment that needs to be done.

[ECR]

I have a Jenvey setup on a16v Vauxhall. This was fitted by Steve greenald of road and race who should know his way round the assembly. My cover plate is on the outside of the assembly and has no spacer. 
I do find that tightening the fixing screws during setting of the throttle pot position is very critical and affects the voltage readings on Easimap so perhaps you are right in suspecting that the pot distorts somewhat

[DW199]

I have just tried it again using some thick strong flat washers under the screw heads to spread the load.  However hard I tried I couldn't cause the binding.  I removed the washers, tightened the assembly again and the binding returned.  I am therefore reasonably confident that the cause of the problem was distortion of the tps body as a result of the screw heads bending the cover plate when overtightened. 

[ECR]

I'll give that a try. Well found ....

[DW199]

Bear in mind that I have a Sigma engine with a single throttle body so the problem and solution for Jenvey throttle bodies may be different.  I believe Oilyhands is Dave Andrews so I would definitely follow his advice.  if you take a look at his web site http://www.dvapower.co.uk/ the section on fitting Jenvey throttle bodies shows an M6 washer on each side between the tps and throttle body to avoid binding.