Dearest all,

My B28 engine (760GLE) had the 3 screws on top of the air intake supposely for adjusting the RPM. problem is that in Haynes manuals, it is recomended to adjust only the one screw at the nearmost to the air intake manifold. What are the other screws for? I'd adjusted all three screws cause before this the two screws is tightly locked and it makes the engine nearly stalling everytime I release the accelerator.

Secondly, the transmission (AW71) jerks hard everytime I release the accelerator altogether and repress hard.

Hope anybody out there would tell me how since I'm new at this DIY repairs.

Love to own a new Volvo but the price is too steep in my country.

That motor has an uneven spacing between cylinder firings and to smooth out idle the engine uses two different camshaft profiles. The concept behind this is that the cylinder bank that fires for the short interval should be a weaker power stroke at idle than is the cylinder bank that fires for the longer interval. As a result the air flow into the two cylinder banks must be distributed at different proportions. This is only really able to be done with an exhaust gas analyzer attached to each exhaust pipe just behind engine and then you switch a valve back and forth while the screws are finely adjusted until the CO levels on both banks are as equal as can be obtained. Then the third screw the manual mentioned becomes the total air flow screw to set base idle speed and the other two are not touched.