Thread: D1 3.9 air leak

Are you sure it's a vacuum leak, and not the standard dirty stepper motor problem?

Does the idle vary to the point of stalling, especially in gear (or not in Park or Neutral) and when warmed up? If so then give the stepper motor a good clean.

And another question, are the replacement dissy cap and rotor genuine Lucas? If they are aftermarket, then that would probably not be helping.

the MAF is new and is working fine, the dizzy im not sure what brand they are but i'll definatly check that out. it the 5 speed manual box but im on the hunt for a zf4hp22 auto box at the moment . cheers for assistance

Ok, so you've checked the MAF, but try pulling the stepper motor (idle air control valve, on the back of the plenum) off and giving it some love with a soft wire brush and and some carby cleaner.

It's a regular problem with these engines, and mine was no exception. If it's gunged up and sticking, the idle goes all over the place.

A common air leak is caused by the fuel pressure regulator's vacuum hose falling off the back of the inlet manifold. The hose is likely to be old and perished.

After cleaning the idle stepper, also clean the throttle butterfly and play with the base idle speed. That is a 3/16" allen screw set in a recess on top of the throttle housing.

ok yer i havnt even had a look at that idle stepper motor. im hoping thats all it is, what is optimal rev range for the 3.9 rover v8?