Balancing throttle bodies

[Glyn Harper]

Chaps.. I'm at my whits end with my tickover.. My car constantly rocks from side to side when idling. I've done my best to balance the throtle bodies by 'feel' (ie, the car stops rocking a bit) but then the idle ends up needing adjusting.. then the fuelling requirements change because the throttle pot is reading a different setting.. etc.. etc..

Does anyone know the correct process, and what the tools are to properly balance the two throttle bodies?

I've seen a 'twinmax' thing that looks quite good, but it needs connecting to little take off ports, which ours don't have.

I've also seen these synchrometer things, but I don't know if that'll do it.

There must be a proper process.. I know the manual says 'don't do this at home'.. but I need to do it, so I'm stuck with finding a solution!

[hilly]

You need something like this Balancer Clicky.

You can do it by placing a tube across the inlet trumpet and listening to the the sound made and adjusting them to all be the same, but the balancer above will give much more accurate results.

Hilly

[Guest Troy Halliday]

I used one of those to set the throttle boddies up on the Lotus 7 Replics I built. They work a treat. But here is a tip, make sure that some lemon does not blip the throttle while you have it in the trumpets as it buggers them right up. Yep I am going to have to get a new one cos someone wanted to sit in the car and there big feet hit the throttle

[Glyn Harper]

Thanks for that chaps. I've ordered one of those clicky units. Hopefully the postal strike won't delay it too much!!

And I'll bear in mind about someone blipping the throttle.. I have my seat so far back anyway that few people can even reach the throttle peddle!

[Drfatz]

I think mine might be way out of wack as well. Will this approach work on a 90 SE?

[Glyn Harper]

The process on your car should be the same as mine, as it's the same throttle bodies.

Only issue you'll have is that there is a funny nut on top that you have to loosen off. It's not a proper nut though, it's like a round nut with slits in it.. presumably there is a special lotus tool!

I took mine off and was going to replace it, but it's a really weird thread (imperial extra fine or something) so you'll never get a normal nut.. endep up linishing flats on it so I could use a spanner!

You then need to get under the balancing linkage with a stubby flat blade screwdriver.

As someone said to me, there are so many factors affecting tickover speed and balance, it's always a sum of all those factors. If you start of with the throttle bodies balanced though, and then sort the other bits out then that's the correct approach or you'll always be chasing an engine that 'hunts' or rocks from side to side like mine does.

I can't wait to see how much out of balance mine are.. once my synchrometer arrives that is! Don't you just love our hard working postmen, eh?!

[Drfatz]

I assume the best way to get at the throttle bodies it to remove the intake plenum such that the throttle bodies are exposed? I am not entirely sure I know which nut you are referenceing for it has been awhile since I really took a look at the throttle setup! :laughing:

[Glyn Harper]

Just take the plenum cover off.. THere six bolts on the back, and two that go through the cross pipe. This will give access to the inlets.

YOu can only take the whole thing, including the backplate, by removing the who inlet system from the car.

The nut is on the balancing linkage.

[Glyn Harper]

Balanced my throttle bodies at the weekend. It's actually a really easy job! Should have taken some pictures I suppose, but didn't really have time and my hands were filthy!

All you do is remove the plenum box (just the end part) and then you can see the throttle 'trumpets'. I say trumpets, they're actually just a moulding in the backplate.

Once you have access to them, run the engine, and place the synchrometer thing in each trumpet one at a time. They are paired.

I found that the readings I got were 6 on number 1, 5 on number 2, 18(!) on number 3, and 17(!) on number 4! So, slightly out of balance then!

You then need to slacken off the nuck a bit on the cross linkage (needs a special tool, unless you've already had the nut off and filed flats onto it!) and then you can adjust the balancing screw.

What you find is that 1 and 2 stay where they are, and 3 and 4 move when you adjust the screw. I had to increase my tickover halfway to stop it stalling.

I managed to get everything balanced really close.

I'd like to say the car is much better, but it's still a bit 'wobbly' on idle. However, I now know my throttle bodies are spot on, so I can look at things like injectors now.