My 94 5.8 non MAF is running lean, slight miss and pings sometimes under load

Things i have done
Replaced rear fuel pump (FP is now 28-30 psi at idle on front and rear tank)
new FP regulator
timing at factory spec. 10 BTDC
Plugs
wires (made sure correct routing)
cap
rotor
injector cleaner in gas
sea foam in intake

kind of at a loss now and need some help!

EGR valve?

 

Check all hoses for vacuum leaks.

 

30 is a little low.



Did you replace the whole FDM, or just the pump motor inside?

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Yes, you can temporarily block off the EGR by removing it (or the supply pipe) & reinstalling with a piece of Aluminum foil across the port. Don't leave it that way - it can damage the engine. If the missing stops (don't do this at the same time as ANY other work, or you won't know which one affected it), remove the foil & see if the miss returns. Check the brake booster by crimping its hose.

But the more-common vacuum leak on those V8s is the plenum-to-intake gasket (#52), and you need a long T40 to remove one of the plenum bolts. The unlabelled stud near #56 can also be a PITA.

 

I replaced the whole fuel pump assembly. I have changed the fuel filter and still the 28-30 psi at the rail. If i take the vac line off the regulator it jumps to 45 psi. I have checked for vac leaks as before i had a problem with the cold air blowing out of the defrost vents when going uphill. I found a leak and fixed it and that problem went away. I will give the EGR valve a go and check for more vac leak's

Thanks

 

A 15psi increase when disconnecting the regulator vacuum line is pretty high. Normal is 5-10. So that suggests the regulator is the source of the low fuel pressure.

 

that's what i thought. I changed the regulator and the fuel pressure is the same. i guess its possible i got a bad regulator. what sort of vac reading should i be getting at the regulator at idle?

 

All red vacuum lines under the hood are direct manifold vacuum. For more about manifold vacuum, read this page & the next:
http://www.users.bigpond.com/ergoff/vac1.htm
Here's another:
http://www.secondchancegarage.com/public/186.cfm

 

Plenum gasket has probably failed. Spray carb cleaner along the base of the upper plenum while the engine is running. If the idle goes up, you have a vacuum leak at the gasket. Removing the plenum will reveal a broken paper gasket. The 92 up 5.0 doesn't blow this gasket due to the fact that they replaced the gasket material at the factory, but the 5.8 still has paper gaskets.

 

Ok im getting 20-21 inches off the manifold the needle moves between 20 and 21 as the rpms rise and fall rhythmicly. sprayed around base and no change, clamped brake booster line no change...........

 

Well i think i have found the problem. I took the egr valve off to inspect it and found the supply tube is broken around the flex. So i guess its been pulling in fresh air when the egr is open.

 

My fuel pump went out recently. I changed just the pump on the sender. Now I have both banks running lean... Any suggestions?

 

How do you know it's running lean? Are you getting fault codes for rich adaptive limit?

 

I pulled the codes with my scanner...

 

I'm getting bank i and 2 lean codes.

 

What are the code numbers and the complete definitions?