i have a 91 2600i thats running rich high idle and the idle jumps from a 1000 to like 2000 and back down to under a thousand check vac leaks none plugs r all black from running rick black smoke out the pipe has anyone had this problem just don't want to start throwing parts at it and the check eb=ng lite is not on

 

Fuel injected right??? Mine did that, but it's a carb setup and I just got rid of the carb and bought a weber.
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Have you checked the ecm? These trucks are known for ecm problems. I recommend this guy: http://www.avproecm.com/ He repaired the one from my truck almost 4 years ago. Good luck.