I've got a 2ltr zetec fitted with Jenvey throttle bodies, the ones which look like twin weber 45s. I just got a airflow balancer to check that the linkages were set correct between the two units. All started well, the rear two inlets showing, as an example, "5" on the scale. The next inlet on the other throttle body showed "4" so two mins adjusting the linkage and that too was showing "5". So now in theory the two units are balanced....but I then decide to check the last inlet and that is showing only "3"! . I took the plug out for that cylinder and it is slightly sooty so looks as if it is low on air and slightly rich. With the plugs out I compression test the engine and all cylinders show well within 5%, so looks as if leaking piston ring or valve is not to blame. The gaskets are as new so I'm a bit stuck as to the cause, I even swapped two injectors round, just a shot in the dark, and no difference. As the two butterflies are linked together on the same spindle they can't be adjusted individually...I suspect that the butterfly not opening as much is the most likely cause but before I send of the body to be checked anyone any ideas?
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I dont have bleed screws fitted, they just need to be drilled thru if they are needed as the hole and thread is cut. the gaskets are standard Ford ones, not "O" rings. The bleed screw is an option but makes balancing a bit tricky...

Hard to see if the butterfly is open less as the difference would be very small, they all look closed when idling as the gap is tiny.

[Edited on 22/10/07 by zetec]

Could you try pushing both butterflies to see if it makes a difference to the idle.....

Also, you could try putting you hand over each TB an see if you can hear an air being sicked in...Only taks a very small lead to make a difference....

Is it easy enough to swap the injectors over?? - could be a dodgy injector also i guess.

Tried swapping injectors and still the same. Took the TBs off yesterday and gaskets all OK. Spoke to Jenvey and they say to post them back to them and they will check them, will let you know what they say.

What heppens if you cover them (one at a time) with your hand....does this stall the engine?.