Hello Everyone
I got a 99 GMC Jimmy 4dr SLT 4.3 with a Intermittent P0507 high idle condition it likes to run at about 800-850ish RPMs. the Service Engine Soon light will come on while driving usually stay on for a couple of days then shut off randomly after just starting the engine. Despite having the code the Engine and Trans run fairly smoothly with little issues. Also the engine as well as the car has had some upgrades such as a new catalytic converter installed the P0507 was there before it was installed. And a new fuel pump to fix the notorious gas gauge stuck on E which also threw its own code but i don't remember what it was but its gone. I have recently recharged the AC System because it gets Stupid hot here in the summer and I have been running it a lot and it seems to bring the RPMs down to 600-700 where it should be, depending what accessories and components are running such as the AC and the Fan. and most of the vacuum lines for the engine are new and get good vacuum pressure there are no leaks causing the engine to rev up as anybody would expect. but my fuel economy is also poor the roof display says about 9.5 mpg avg. I'm not sure if these issues are connected but i do know that these blazers / jimmy's aren't very fuel efficient but i feel like it shouldn't be that low even for city driving. I do "romp" on it a little occasionally but it shouldn't affect it much i don't think. I am thinking there may be a chunk of carbon build up in the EGR system causing some issues. what are some things to check or do such as cleaning the sensors and valves. Also i daily drive my jimmy so I don't want to take it half apart i just want some simple tips and pointers to remedy this!