Vacuum leaks usually tend towards low end of wandering idle (engine starts to die). May rev to other side after it catches itself, but never any further than throttle plate setting (usually set too high due to leak). Stock DeLo of course doesn't idle off throttle plates. Idle speed motor can open up to 3/4" air passage -- equivalent to 20% or more of plate action (anybody know actual diameter?). Your automatic idle system may be twitchy. THIS is why I recommend all owners should be familiar with manual idle circuit built into upper air assembly. Even if not used as primary system, does allow automatic circuit to be disabled for diagnosis. Contact me off list (brobertson(at)carolina.net) and I'll send you a Volvo procedure. Bill Robertson #5939 >--- In dmcnews@xxxxxxxxxxxxxxx, "Jonas P" <Delorean3543@xxxx> wrote: > This problem usually only happens on cold starts. After starting my > 81 D the engine races up and down. At an idle in park it sounds like > someone > is pushing up and down on the gas peddel. When you put it in drive it > still happens but not as bad. Sometimes I can rev the motor to around > 4000 RPM's a few times and it quits. After the motor warms up a bit > it stops. I know for sure I have a vacaum leak, John Harvey is > putting > together a silicone hose set to replace my old ones. Would a vacaum > leak cause this type of problem? If not, Anyone know what would cause > this? > Thanks > Jonas 3543