If that O-ring is not there then you have 2 problems. 1. There will be a vacuum leak and 2. Yes it will cause the plunger to be off since now the distributor is sitting slightly lower. Remember....the slightest maladjustment can cause the entire fuel delivery system to go out of whack. To answer your question about adjusting the air/fuel mixture: You will need a CO analyzer a 3mm Hex key and patience. Some people have done the adjustment without the CO analyzer and used a Volt meter but to do it right you will need a CO analyzer and take the readings from the tap ports on the cross over pipes. I would leave the CO adjustment to a competent garage since the analyzers are fairly expensive. Steve --- In dmcnews@xxxx, "deloreanfl" <ericp@xxxx> wrote: > Hi Mike, > > Don't forget to install the rubber O-Ring that goes between the fuel > distributor and the mixture control unit. I was told by several > people that this wouldn't make a difference, and wasn't needed - but > I forgot to replace mine one time...and had EXACTLY the same result > you are having. My guess is that it raises the plunger pin just high > enough from a rest position to make a difference. But hey, this is > my guess: All I know is that my car wouldn't work without it! > > Good Luck > Eric > Dunedin, FL > deloreanfl@xxxx > > > > --- In dmcnews@xxxx, Senatorpack@xxxx wrote: > > > > > > Hello DML, > > > > I'm helping out a new owner tune up his car and replace the > fuel > > injection system. We have reset the car back to factory settings. > However we > > have encountered a small adjustment issue. > > > > Installed new fuel distributor and control pressure regulator, > etc., etc., > > on new owners car. What is proper way to adjust air/fuel ratio? > > > > Engine starts, however only runs when fuel distributor is free > (loose) > > from mixture control unit. (Fuel lines attached) > > > > i.e. Engine will stall when three screws to attach fuel distributor > to > > mixture control unit is secure. Engine will run when screws > removed, however > > idle is rough. > > > > Seems as though the plunger on the bottom of the fuel > distributor is out > > of sequence with the air plenum arm beneath the air box. > > > > This is the first time that I have seen the air plenum and fuel > distr. > > plunger is out of alignment. > > > > Thanks > > Mike