I have a friend who has a 74 SE450 with a V8. The car is always hunting for idle or reving out to high in idle. What could be the problem. The air idle screw is screwed in all the way. Air leak ? Anything common for this engine ?

Aux air valve stuck (fairly common) or a leak in the idle air hoses or mainfold seals/MAP sensor line.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Can you buy all the hoses somewhere ? What about this MAP sense line ? Can you check it somehow. Also the AAV can you take it apart and clean it or check if it is sticky ?

Check on FastLane on this site for idle air hoses.

The aux air valve can sometimes be cleaned.

The MAP sensor is on the fender, I think -- long vac line about 1/2" diameter to the rear of the manifold. If the hose is hard, replace it. You will probably have trouble finding a metric one, so if you go the the auto parts store, get one that is fractionally SMALLER -- the slightly larger one will leak.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!