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Old 05-27-2016, 06:12 PM   #2
not this alero
AleroB888's Avatar
AKA: Greg
Join Date: Nov 2005
Location: Fort Knox area, KY
Age: 68
Posts: 1,298
Vehicle: 1999 Alero V6
AleroB888 Gettin' there
Part II

I have now replaced these ignition-related part in the system:

Cam sensor,
different coils and ignition module (whole assemblies),
new plug wires,
different crank sensor (rear of engine block),
MSD DIS unit has been removed to simplify things.
Crank pulley and sensor
Upper intake gaskets replaced with thicker ones to make sure manifold clears fuel rails.
2 different sets of injectors.

Oil changes were done again at about 65 and 400 for a total of 3.

I have put a little over 600 miles on it.

During the first 200 miles, a line from the PCV valve got plugged, forcing some vapors out the back valve cover tube. But away from the PCV lines, oil seeps down along the edges of the front head gasket and drips from the corners. It has not been nearly as bad since the PCV line was cleared, but there is still some dripping down both edges of the gasket. It appears to happen only when the engine runs, and does not drastically affect the oil level after a couple hundred miles. The leak appears to be from the LIM/block seam, near the throttle body

So I still have the engine vibration and the misfires when idling or cruising at low speed below about 1500 RPM. The engine starts well enough cold and continues to run, as long as it can warm up for a few minutes. But backing the car out of the garage just after starting can cause it to die.

When fully hot and on the road it does better at high RPM, but it has trouble maintaining idle at stoplights, and surges cruising at low speed. When it is fully hot and then shut off and parked for about a half hour, restarting is very difficult, even if resorting to opening the throttle.

I put a stock front trans mount back on, but the engine itself moves around more, even though less vibrations get to the chassis.

Sets the P300 misfire code. When deleted, it comes back every other startup. The misfires occur on all cylinders, but are more numerous on cyl 6, then cyl 5 is a close second. Misfires disappear around 1500-2000 when cruising, and are not showing up cruising at over 50 mph or so.

Delivered Trans Torque scans 45 ft lbs more than a bone stock vehicle. Has decent power off the line. (still normally aspirated)

I don't think synthetic oil being in there at first start caused this, since it was changed after only 3 miles and 20 minutes of driving. The excess oil pressure at first startup I'm worried about, though, and I wonder if that caused the oil leak at the LIM/block junction.

Need some informed speculation on possible causes...

Thanks for reading (whew).
1999 GLS MP90 supercharged / 2003 GL MP62 supercharged / 2004 GLS stock
Magnuson MP90 / TOG's / 3 in. Magnaflow exhaust / MSD ignition / LS1 MAF / Racetronix pump / HP Tuners / TCE 68mm TB / 36 lb Inj
= Best track time: 12.951 @ 104.48, 1.839 60 ft. (Beech Bend Raceway Park, 11-23-13), 50 Deg. F
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