92 f-150. New NAPA reman engine about 12000 miles ago, very mild comp cam (not sure what one), new EGR, new ford motor sports 19 lb injectors. wires plugs etc, maybe more but cannot rember. Gets really bad millage, 8-10 hwy, bogs down on the mountain passes, no readable codes.... This is all new sense the new engine, the old engine with 200k ran allot stronger and got about 14-16 mpg hwy. The other problem I am having with this engine is that at idel and up untill it starts to rev over aprox 1900-2000 there is a noteacable hisistation, like a missfire. Watching the tach you can see the RPMs drop about 25-75. Also the trucks idel speed is very irregular, some times it will idel at 1200, other times at 1000 and at 800, if you flog the gas, most of the time it will return to 800 rpms, however these last two ideling issues are not specific to the new engine, the old engine did the same thing. THe timing is set at 10 BTC with sprout disconnected. Wiht it connected timing is about 20 or so and advances up to maybe 38-40. Are there any ideas of what i can look for, I have posted these same problems before but thought I would give it a try again, this gas millage is killing me and I am at a loss for what to look for.
Thanks

 

Sorry i reran the codes and there were two in memory, 332 and 337, EGR did not open intermittantly-EVR or PFE and EGR feedback signal is/was high-EVR, could these be affecting the above mentioned problems? The EGR as well as the positioning sensor are new.

 

getting the cam specs is important, because it may be the incorrect type for you application. also may have a bad TPS or IAC solenoid

 

Yeah, EGR problems can cause the truck to idle and run like crap.

But what Kemicalburns said is right on too.