Hello all, I have a 94 f150 with the 4.9l and E40D auto trans. It has AC and is 2whl drive. My problem is this. I had severe spark knock about a year ago and decided to rebuild the engine (almost 200k). Heads were in great shape however there was slight scoring on cylinders so pistons were part of the rebuild. rebuild went well however, and needless to say, I still have severe spark knock at idle. timing hovers between 4 btdc and 0 degrees. The MAP sensor tested good using a vacuum pump and a digital tach on meter. it went from 320 rpm at 0 inches vac to around 190 at 22 inches. There is good vacuum at idle ..or I think there is, its 20 pounds but drops to almost 0 as it surges. i checked all components that use a vacuum sorce for leaks and even bypassed them and same condition still occurs. I am currently bypassing the "vacuum cannister" as it was leaky. i will make a new one tonight out of 3" pvc.
The EGR vacuum solenoid was bad, the coil never activated, so it was replaced. I am not even sure it is coming into play.
I ran the DLC test for EEC-IV codes and here are the codes i retrieved.
KOEO test 33 and 133. KOER test gives 532, 536, 538.
if I unplug a vacuum manifold port the engine will idle but timing still sits aroun 4 dbtdc and 0. and of course engine gets hot. i get spark knock bad so i cant run the engine very long.
fuel pressure is 50 static and around 42 with engine idling.
I will do more electrical tests later. there are a lot of checks for the EEC-IV that are manual, I guess I will go through them later.
Any advice as to what to check would be appreciated.
Thanks so much, Tim