Volvo Repair: 84 Volvo 240 surging idle, fuel pressure regulator, vacuum leaks

Question
Bilbo,

Thanks for looking into this question. I have an 84 240 wagon with 254k miles with an unsteady idle: it idles at about 750 rpm but will surge at 1 - 2 second intervals to 900 rpm. This is worst when the engine is cold, but also occurs after the engine has warmed up. Main fuel pump was replaced 6 months ago; plugs, cap, rotor and air filter over the last week.

Any advice on where to look for to solve this problem is greatly appreciated!

Answer
Greetings,
       There are many reasons why your engine could run unevenly..at idle...leaking fuel injectors,vacuum leaks at hoses or manifold areas leaking vacuum....fuel pressure regulator....problems with fuel pump or related parts in fuel tank... I'm sure that there are more...my first guess is check the fuel injector spray/leaking pattern....oxygen sensor??...

             Good luck...to you,

         Bilbo