OK I just removed/reinstalled my intake manifold. I put in new plugs and new MSD SuperConductor wires. Everything seems good, except there is a very regular stumble. It's fairly fast and RPM-dependant, but it comes and goes.

I THINK I may have not seated a plug boot all the way, so I may be getting misfires on one cylinder. I'll be checking that first thing in the morning. But is there anything else that would cause this, anything else I should check for?

 

Incorrect plug wires routing...easy to swap a few and you'd be suprised at how well a SBC will run with swapped wires...

Also, do you have good seperation in the wires?

 

I am pretty sure the wires are routed correctly, but they run very close together. Is that likely to be a problem? They touch in places... I guess I can try to seperate them but there's not a lot of room if I want them to avoid touching the manifolds.

 

OK The wires are on the right plugs... And I got the one wire to snap onto the plug. And the stumble is still there.

I don't think it's fuel related, the injectors look like they're firing fine. I don't think I have a vacuum leak, the stumbling seems to regular, and it's RPM related. I'm still suspicious that it's an ignition problem but I don't know what to check! Any suggestions?

 

Geeze, where is all the help today?

Doesn't anyone have any ideas?

Further info:
The stumbling is load-dependant and RPM dependant. High RPMS = many stumbles per second, low RPMS = few stumbles per second. High-load (acceleration and uphill driving) situations, very noticable. Low-load (idling in neutral, coasting downhill), much less noticable.

It seems like it may be affected by engine temp too, it seems to get more prominant as the engine warms up. But it's hard to tell.

I put a timing light on plug wires 1, 2, 3, 4, 5, 6, and 8, got the light flashing on all of them. If there was no spark on one plug, the light wouldn't flash right? I was about to check plug wire 7 when my darned light broke.

 

EJ,

Just for a refresher, what year/engine/fuel system do you have? You problem could be something common to all engines, or specific to your fuel system.

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Later,
Vader
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"Make Me Bad"
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I've got an L03, Vader. But I figured it out on my own... The problem could have happened to any fuel system, it was a bad spark plug. I finally decided to yank all my plugs and look at them, see if there was one that looked like it wasn't firing. I got to #8, and when I pulled the boot off, the ceramic part of the plug came with it :-). So I put the 7 good plugs back in cylinders 2-8 and one of my old ones in #1 (the easiest cylinder to change plugs on ), drove to Autozone and swapped my broken plug for a good one. Problem solved!

Unfortunately I'm not 100% satisfied that my original problem (the one I resealed my intake manifold for) is gone :-(. We'll see tomorrow morning when I go to start it and it's stone cold...