Cant bring the idle down after tearing the truck apart

[rangerin]

I just finished swapping the auto trans out for a M50D in my '84 ranger. While at it, I took the motor out and tore it all apart to clean it and do a full reseal. I did take the carb apart, but only a little. I changed a few gaskets that were leaking, but I didn't remove any mixture screws or anything that would "mess it up".

Problem: I can't bring the idle down at all. I checked for vacuum leaks and have none. In the past, the truck would hold a steady 20 inHg at idle. Right now, its barley gets 11 inHg at idle. Also, the motor knocks a little just before dying when I bring the idle down via the idle speed screw. I've tried messing with the two air/fuel mixture screws, but can't get any improvement there either. The distributor is set correctly also. Any help is much appreciated as I've been working on the truck everyday for 2.5 weeks and I just want to drive it!


Truck specs:

2.8 motor
Holley carb
Durasparked (as a result, all emmision stuff ripped out)
Timed to 12 degrees (truck runs better @ 12 since durasparking)

 

[RonD]

Sure reads like a vacuum leak with 11" at idle, and the knocking just before stalling, lean mixture knocks.

Partially block off the carb's air intake while idling and see if you can hear vacuum leak.
I often remove fan belts, on cold engine, when trying to track down noises or leaks, without the fan noise engine bay can be much quieter, running cold engine a few minutes without water pump is fine.

You can spray Carb cleaner or Quick start(ether) around gasket areas, COLD ENGINE, and see if RPM changes, if it does then that's the area of the vacuum leak.
The reason for the COLD ENGINE is that both of those fluids can ignite if they come in contact with hot exhaust manifolds

If you have a compression tester I would check a few cylinders, just to be sure pistons and cam(valves) are timed correctly, above 150psi would be expected.

 

[rangerin]

I was thinking the same thing about a vacuum leak. Problem is, I can't find one. I've been over all vacuum connections and the carb and have sprayed everything with WD-40. I dont have a compression tester, but though the 2.8 can only be assembled one way. Both the crank and cam gears have a key that only lets them go in a certain way. I also made sure the timing marks on the two gears were lined up too. Is is possible cor the cam timing to still be off?

On the plus side I checked my oil pressure and I get about 60psi. I did take it for a short drive and the transmission and clutch are super smooth.

 

[RonD]

Well I would still cover the carb air intake, that should be the ONLY way air can get into the intake, if engine is still running with little air going into top of carb then it is getting the air from someplace else.

Another method is to remove all the vacuum lines from carb and intake one at a time, see if idle changes(or see if vacuum meter changes), if it doesn't then cover that port with your finger, if idle does change now then that line/hose is OPEN at some point, follow it.

 

[rangerin]

Found the problem! It was the EGR: http://www.therangerstation.com/forums/showthread.php?p=1482854#post1482854