I have a LH2.2 that doesn't respond very well to an increase in the idle adjustment screw. The idle reads at about 650rpm, and bentley quotes the ideal to be around 750rpm. But when I unscrew the idle screw the RPMs don't increase. But if I screw it in then the rpms decrease.

I almost unscrewed it out of it's socket when trying to get the rpms to increase. Does anyone have suggestions for action to take? I have cleaned out the throttle body already, although I only cleaned the butterfly valve. Is there more cleaning to be done there?

I am going to replace the fuel pump check valve because she doesn't start up until the second crank, but always starts consistently. Could this be related? Also the idle is a little rough and I can find no vacuum leaks under the hood. I was thinking this might be due to the low rpms?

Any suggestions appreciated. Thanks!