tbi question

[bighutch]

I have a 1987 suburban with a tbi 350. When the truck is idling it fluxuates between 500 and 800 rpm back and forth back and forth about every 2 seconds or less. Anybody know whats wrong.

 

[Can Can]

It sounds like a vacuum leak to me, brother. Take a close look at all of your vacuum lines, as well as the throttle body base gasket area. Start there and let us know what you find.......

 

[4X4HIGH]

Do you have A/C and if so make sure that the pump doesn't keep cycling off and on. When the A/C is requested the ECM raises the idle and when the A/C compressor shuts off then the idle drops as well. Just a thought and a place to start checking if you can't find any vacuum leaks.