1997 gmc yukon idle acting up

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nicksuspect

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Hello friends. Out here for some wisdom. Been having an issue with my idle and going up hill stumbles. No codes. Almost everything is new including the engine. Used only gm genuine parts. We set our timing at dead on 0 cam retart. With a flashlight I was looking around the block and saw it was seeping oil from the front of the lower intake manifold straight in the middle of the valley. Was wondering if this leak could be causing me a misfire. I've had this issue before with my old engine but it was fixed with new intake gasket.the only thing I haven't replaced new is the egr, crankshaft position sensor,connector to crankshaft position sensor
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nicksuspect

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So I got a new egr cuz no matter how much I cleaned my original it would still get stuck coming back up. Possibly vacuum leak. Still stumbles but not as badly or as much. I'm kinda of thinking it's pulling vacuum from the front of the intake manifold where I'm having oil seep out from. Ima try and do a smoke test see what I can find
 

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So I ended up removing my Idle Air Control and not only was the o ring warped but it has so much carbon build up. Strange thing is I don't use cheap gas I always use 91 octane fuel. The last time I took my intake off which was recent I remember cleaning the crap out of this but then again I never actually took the sensor out I just cleaned it while it was inside the throttle body. I'm wondering if I should even try to clean it. And if so I'd still need a new o ring. Or buy the delfi one- which I've heard doesn't work as good as the original
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O-rings are cheap. Pintle doesn't look that bad to me. Maybe there's carbon on the seat interfering with airflow. Clean it, and the seat, get an O-ring, and see what happens.

"No codes" doesn't mean much. Connect a scan tool, verify EVERY sensor and computer output.

Seems to me that if there were a big problem with oil seeping OUT of the manifold seal, there can't be much air getting IN. If there were, the oil would be pushing out. I'm not saying you don't want to fix the oil leak, just don't expect it to make any difference in how the engine runs unless the infamous intake gaskets have issues.
 

missouritig

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Run a fuel pressure test before you go any further. My 5.7 vortec ran absolutely terrible and never threw any codes. My fuel pressure was a little weak, but not terrible. Ended up being damaged spark plug wires. I replaced leaking mpfi spider injector, replaced spark plug wires, distributor cap, rotor, and ignition coil. Runs awesome now
 

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O-rings are cheap. Pintle doesn't look that bad to me. Maybe there's carbon on the seat interfering with airflow. Clean it, and the seat, get an O-ring, and see what happens.

"No codes" doesn't mean much. Connect a scan tool, verify EVERY sensor and computer output.

Seems to me that if there were a big problem with oil seeping OUT of the manifold seal, there can't be much air getting IN. If there were, the oil would be pushing out. I'm not saying you don't want to fix the oil leak, just don't expect it to make any difference in how the engine runs unless the infamous intake gaskets have issues.
Yeah I cleaned it out a new o ring and still trips on idle. What should I look for in the scanner that would be abnormal? I took some pictures of where the oil keeps going out. My fuel trims are showing pretty lean but I was driving about 60 mph. My spider injector assembly is brand new gm genuine and also my fuel filter. My fuel pump probably like 1 year old Delphi pump. from.
 

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nicksuspect

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Run a fuel pressure test before you go any further. My 5.7 vortec ran absolutely terrible and never threw any codes. My fuel pressure was a little weak, but not terrible. Ended up being damaged spark plug wires. I replaced leaking mpfi spider injector, replaced spark plug wires, distributor cap, rotor, and ignition coil. Runs awesome now
The majority of those things are brand new. I just put this engine in. Has a new distributor new plugs new wires new injectors.
 

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...and old wire harness supplying power and ground to the pump. If the pump is starving for power, it's not going to produce appropriate fuel pressure.

Test the pressure to be sure.

Verify that the IAC works.

Video is worthless. I can't read the screen.
 

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I'll check the pump harness tomorrow. I did check the ground wire and it was still intact didn't look broken . These reading was at about 60mph.
I'll test further tomorrow. I am still gonna open it up tomorrow make sure the injectors aren't leaking by taking the pegilum off. What pressure is it supposed to read at and how long should it hold pressure
 

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nicksuspect

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So I did a smoke test and I had a bunch of smoke coming from the timing cover. Could this be considered a vacuum leak. Had no leaks anywhere else
 
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