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**kwmech** · 02-16-2018, 01:23 PM

Boy, talk about a thread Hijack!

Back to the original OP. Sounds like you may have a vacuum leak in the system. Most common is the gasket underneath the TBI or the TBI adapter. With the engine running, spray some carb cleaner around the base of both and see if the idle changes. Also check the vacuum line to the MAP sensor. Actually check all the lines for deterioration or cracking

02-16-2018, 01:23 PM	#11
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: 89 C 3500 7.4l TBI with issues Boy, talk about a thread Hijack! Back to the original OP. Sounds like you may have a vacuum leak in the system. Most common is the gasket underneath the TBI or the TBI adapter. With the engine running, spray some carb cleaner around the base of both and see if the idle changes. Also check the vacuum line to the MAP sensor. Actually check all the lines for deterioration or cracking