New motor issues.

[LakeRat32]

Ok folks, let's see if the collective can help diagnose an issue I am having.

I've got a 96 Tahoe, 5.7 Vortec. Just replaced the motor with a GM short block. Added parts are as follows:

MSD 6AL control box.
MSD Streetfire distributor.
MSD wires and coil.
Powermaster 240 amp alternator.
Pace Setter shorty headers.
GM Spider injectors.
NGK Iridium plugs.

And now the issue. I got everything transferred over from the old motor that was still good, plus a few sensors and stuff that were replaced. Poured the oil, trans fluid, and turned the key.

At idle, it is rougher than slidingnon 30 grit sandpaper, lopes like it has a cam(it doesnt), and stalls when I shift into gear. There is a miss on cylinder 3 and 6, and I chased the wires 4 times making sure they were on the right plug and distributor point.

I've got all the vacuum lines either capped or ran correctly. I am not using the smog can, so I disconnected and capped those lines. The EGR and PCV are brand new.

I pulled the plugs and none are fouled or burnt. And the control box is not miswired or shorting.

I've read about a fuel pressure issue, but I don't think that's it because nothing was wrong with the fuel when I pulled the old motor, i spun a couple main bearings and gouged the crank. So I don't think it's a fuel issue. My line of thinking is either timing or vacuum based on what I've experienced in the past with motors and what I've read on some forum posts.

Has anyone seen this happen, and does anyone have an idea on what could be causing it?

 

[willxfs]

Not too sure. Sounds like it could be timing. I found the write up in the following link to be very helpful when I was setting the timing on my motor. I installed a rebuilt 383 in my rig with a reman delphi distributor. I couldn't get the edge (as depicted in the third picture) to line up with the edge of the camshaft position sensor. I ended up having to remove the gear on the bottom of the distributor and rotate it 180 degrees. Once I did that the everything lined up just as the write up describes. All was good. Just had to use the scanner to set the cam offset retard to + or - 2 degrees. Also be sure you are at TDC on the compression stroke. I see you you have a different distributor so not sure if the write up will apply. Good luck. Keep us posted.

http://www.gmtruckcentral.com/articles/distributor.html

 

[swathdiver]

Chase them wires again, with another set of eyes maybe. Check the gap on the plugs.

 

[Upper tanker]

This might sound stupid, but do you have a known good distributor cap laying around? I rebuilt my 350, and bought an msd distributor, cap, coil, and wires. When we did the first start up, I was getting terrible misfires out of 2 cylinders. I re-adjusted the valves about 47 times, but it was still popping out of the tailpipe. Finally, I decided to throw on the original cap back on the distributor, and the problem went away. So, a BRAND NEW MSD cap was the cause of my misfiring. Not saying this is your problem, but it might be worth a check.

 

[LakeRat32]

So I pulled the stick and popped my old stock stick in, and was having the same issue. So that shot me to plugs wires and vacuum. Turns out, I had 3 wires that had slipped the loom and roasted on the headers. Super simple fix, but one I overlooked trying to make it difficult. I did however smoke it and found a small leak in the brake booster, but indent know if that would cause an issue or not.

Now I'm in the process of regearing it to 4.10 and spoiling the rear, upgrades to 38 spline shafts and a full air locker out front. Iv e learned that stock 30 spline isn't very strong the hard way.