Volvo: 1993 volvo 940 idle issues, vacuum leaks, vacuum lines

Question
Hello,
Thanks for taking the time to answer my
question.

I just bought a 940 automatic for $1300. It's in
great condition cosmetically, which leads me to
believe it was well maintained mechanically. I
have noticed, though, that when stopped, the
rpm's fluctuate from about 500 to about 900-
1000 pretty quickly. It kind of reminds me of a
heartbeat, fluctuating up and down in a second
or two, and happening with a regular "beat". It
starts and runs fine, but when at a complete
stop it happens in any gear, ingluding park and
reverse.

Answer
Alexander,
Clean the throttle hosuing of the built up carbon. Pull the vacuum lines off the mainfold and may sure that they are clean not plugged up. Inspect the intake air hose for leaks. Check for vacuum leaks. Read the codes to see if there is a fault code for the idle speed motor. Sometimes they can be cleaned out or you might need a replacement. Move to the fuel system see what pressure it's running. Make sure that the pre pump and main pump are both working. Check to be sure that the fuel filter is not blocked. Fuel pressure should be 42 psi.