1997 gmc yukon idle acting up

[Schurkey]

Air leakage into the crankcase isn't going to affect how the engine runs. Crankcase air is metered into the intake airstream via the PCV valve or PCV orifice. The crankcase has no real vacuum, just airflow from the PCV system and the intake of filtered air opposite the PCV valve/orifice.

The timing cover shouldn't leak air in or out. The issue might be unfiltered air getting into the engine, not the air itself.

 

[missouritig]

Hey so pressure should be close to 60psi on a vortec. If it bleeds down real fast then its likely an injector assembly problem.

before you start tearing into things, do some more diagnosing because youve done some major work that is prone to problems.

First when you say injectors were replaced, where did you get your spider assembly from and is it under warranty?

Did you replace just the upper manifold gasket or did you do both? Do you still have the ground wire for the ignition components somewhere around the thermostat housing?

Also, what distributor did you buy and are you able to see what timing is at idle and at 2,000rpm?

Both of those if installed slightly wrong or if they are off-brand chinese knockoffs can perform terrible.

Do you have any pending DTC codes?

Give some more info about your engine, what kind is it and whats the history.

 

[nicksuspect]

Hey so pressure should be close to 60psi on a vortec. If it bleeds down real fast then its likely an injector assembly problem.

before you start tearing into things, do some more diagnosing because youve done some major work that is prone to problems.

First when you say injectors were replaced, where did you get your spider assembly from and is it under warranty?

Did you replace just the upper manifold gasket or did you do both? Do you still have the ground wire for the ignition components somewhere around the thermostat housing?

Also, what distributor did you buy and are you able to see what timing is at idle and at 2,000rpm?

Both of those if installed slightly wrong or if they are off-brand chinese knockoffs can pebody rform terrible.

Do you have any pending DTC codes?

Give some more info about your engine, what kind is it and whats the history.

I'll be checking it today.. it's an l31 4 bolt main. I bought the injectors from gm. Probably like 3 months ago so yeah still under warranty. I replaced both upper and lower gaskets and the intake itself because my original was leaking bad. Yes my ground is still intact where the thermostat hosing is. I bought the duralast distributor from autozone cuz it had a metal body n lifetime warranty. My original broke from where the cap holds down. They weren't installed wrong we put the timing retart exactly at 0. No dtcs. Engine is new as well. Didn't start doing this this till last week. Was running fine before hand

 

[nicksuspect]

So I just did a fuel pressure check. Goes all the way to 60 only drops alittle bit and stays there. When runing its at 50

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[nicksuspect]

I'll be checking it today.. it's an l31 4 bolt main. I bought the injectors from gm. Probably like 3 months ago so yeah still under warranty. I replaced both upper and lower gaskets and the intake itself because my original was leaking bad. Yes my ground is still intact where the thermostat hosing is. I bought the duralast distributor from autozone cuz it had a metal body n lifetime warranty. My original broke from where the cap holds down. They weren't installed wrong we put the timing retart exactly at 0. No dtcs. Engine is new as well. Didn't start doing this this till last week. Was running fine before hand

So from my tests and what the book says I'm well within specs. Mine probably drops less than 5 and when running is within the 10 drop

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[nicksuspect]

So upon disassembling I come to find oil inside my distributor.? I don't know if you guys ever had this happen. It does have lifetime warranty. Also noticed my rotor was rusty for a new distributor. For comparison the grey one is from my old distributor the grey isn't rusted at all. Could this all be causing my issue. I've read that oil inside could cause the proper transmission of ignition spark cause misfire and run poorly

 

[Schurkey]

So upon disassembling I come to find oil inside my distributor.

Verify entire PCV system including the filtered-air inlet hose to the valve cover opposite the PCV valve.

Oil in the distributor may be the result of excess crankcase pressure.

Wouldn't hurt to assure that the distributor shaft is properly supported by the bushings in the distributor housing. The shaft should turn easily, but not flop around on loose bushings. Proper shaft-to-bushing clearance would limit oil going up the shaft under normal circumstances. (i.e., if there isn't excessive crankcase pressure.)

It does have lifetime warranty.

If the bushings are wiped-out and the shaft wiggles around, return it for another. But excess crankcase pressure could push oil up past good bushings.

Also noticed my rotor was rusty for a new distributor.

Wild Guess: Cheap rotor without proper plating of the metal conductor.

 

[nicksuspect]

Verify entire PCV system including the filtered-air inlet hose to the valve cover opposite the PCV valve.

Oil in the distributor may be the result of excess crankcase pressure.

Wouldn't hurt to assure that the distributor shaft is properly supported by the bushings in the distributor housing. The shaft should turn easily, but not flop around on loose bushings. Proper shaft-to-bushing clearance would limit oil going up the shaft under normal circumstances. (i.e., if there isn't excessive crankcase pressure.)


If the bushings are wiped-out and the shaft wiggles around, return it for another. But excess crankcase pressure could push oil up past good bushings.


Wild Guess: Cheap rotor without proper plating of the metal conductor.

So I checked all my evap hoses and are all good and free no clogs. I checked my evap purge valve and it's good. Then I hit the evap purge vacuum switch when I blew into the breather hose.Air comes out where the connectors connected. That's obviously not supposed to do that. Anyone have information on what that switch does. In the book it says it's supposed to be closed. But I can blow through it from either end. Could this be causing the build up of pressure?. Not letting the air circulate

 

[Schurkey]

The PCV (crankcase ventilation) and the Evap system (fuel tank venting) are totally different systems.

 

[nicksuspect]

Little finds.Crankshaft position sensor wires looks like it was pulled. Also power steering evo sensor wire was exposed tore alittle. Timing cover full of oil. Glad I ordered the holley metal timing cover. Ima keep posting pictures as I go about this whole process let's see how many more surprises I find