Your fuel presure is fine. The fuel pressure spikes because when its "jerking" its problably misfiring, and that's when the intake manifold vacuum drops, causing the fuel pressure to rise. The changes in the IAC are minor. Its not going to cause sudden changes in vacuum. Its the "jerking" that's causing the vacuum to drop.

 

lt4 swap lol..... Ill check all my plug wires again. Should check compression. And I have noticed some oil in the pcv hose and the oil filth around the cap (these were the first signs of my head gaskets starting to deteriorate back when i had my 92' camaro).


And thank you for your help and explinations. I really do appreciate it.

 

Also just a question. Why is there no pcv valve, just an empty elbow. That would explain the oil getting into the throttle body, right?

 

The PCV valve is located in the driver side of the intake manifold. The tube on the passenger side valve cover is just a fresh air supply tube, providing a source of fresh air suction so the PCV valve can evacuate the crankcase gases into the intake plenum. There should not be a PCV valve there. During periods of low vacuum, the PCV cannot keep up and the system will reverse itself, blowing oil mist through the tube into the throttle body. The system is designed this way and a small amount of oil is normal (baffles in the valve cover help to keep most of the oil separated from the crankcase gas). Large amounts of oil could be signs of excessive blowby, which should be noticeable by just placing your hand over the oil fill cap and feeling for puffing.

 

How does it not draw vacuum on the fresh air side?

 

I think i figured the pcv system out, but more importantly I figured out why the engine was missing, well the system causing it to miss. I unhooked the vacuum from the egr and took it for a drive and it wouldnt miss. While i was driving I stopped and hooked the egr back up to confirm and it missed while driving.

 

The "fresh air" hose connects to the port on the side of the throttle body. That port is routed through the small plenum on top of the throttle body (under the cover plate) and the opening emerges IN FRONT OF the throttle blades. There is no intake manifold vacuum in front of the blades.

 

Will there be any adverse effects from disconnecting the vacuum to the egr system, other than throwing a code and a little bit higher timing? I run 93 octane so that should help with the timing even though it advance up to 40 degrees. Also will it run rich, By trying to compinsate for the exhaust gas?

 

Lot's of people disconnect the EGR, incorrectly thinking it will lead to increased power. The only adverse effect would by high combustion temperatures that could lead to detonation and the PCM pulling timing. You will also have higher NOx emissions. The car won't run richer from this deletion....

People will comment that you don't need EGR with a cam with the proper LSA and overlap......that's true.

 

I hope i quoted that right, and thats why the lt4 doesn't have a egr, because of the amount of valve overlap.

Also how would this create hotter combustion, considering your putting in cooler air instead of hot exhaust? And I guess this will bandaid the problem for now.