will give it a try tomorrow. 
Another engine miss
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Another engine miss
About 6 months and 1500 miles ago I did tune up.
79 stock 350 L-48
1. plugs and wires
2. pick up coil, module, rotor and distr. cap
3. timing per sticky
Still had a little miss at idle and when I held the rpm's anywhere higher up. Thought well it could be carb. Did the lars procedure and all did better but not totally, so I decided to change the plugs and check plug wires, old plugs looked good burning lite tan color.
Not sure what to check or do next.
Could it be the Integral ignition coil since it was not changed?
Thanks ED
79 stock 350 L-48
1. plugs and wires
2. pick up coil, module, rotor and distr. cap
3. timing per sticky
Still had a little miss at idle and when I held the rpm's anywhere higher up. Thought well it could be carb. Did the lars procedure and all did better but not totally, so I decided to change the plugs and check plug wires, old plugs looked good burning lite tan color.
Not sure what to check or do next.
Could it be the Integral ignition coil since it was not changed?
Thanks ED
Last edited by ED79; Oct 5, 2009 at 12:45 PM.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Well, if you're going to throw parts at it until the problem goes away you might as well make a list. It may end up being cheaper if you know, can find, or pay someone to scope the ignition primary and secondary. That way you'll be able to tell precisely how the ignition is performing and which cylinders, if any, are laying down.
If the lab scope is out of the question, I would start by shorting plugs to find the bad cylinders. This will narrow it down to specific cylinders or a random misfire. If it shows up as specific cylinders, then you can start checking from there to include a compression test. If it's random, then you can trouble shoot the individual parts. Coils tend to misbehave more when they are hot and that's a good starting point in suspecting the coil. I suppose you checked the switch on voltage at the coil already?
If the lab scope is out of the question, I would start by shorting plugs to find the bad cylinders. This will narrow it down to specific cylinders or a random misfire. If it shows up as specific cylinders, then you can start checking from there to include a compression test. If it's random, then you can trouble shoot the individual parts. Coils tend to misbehave more when they are hot and that's a good starting point in suspecting the coil. I suppose you checked the switch on voltage at the coil already?
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Maybe it should be mentioned it's considered a good idea to keep wires 5 & 7 separated & cross w/ X. I knew about it before I had a car & never had a problem. I bought a Chevy V-8 that was missing & checked 5 & 7 first & fixed it.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I wonder if your describing a lean idle miss. If you are it usually changes cylinders.
If you do have a real miss you can try this. Adjust the curb idle screw to the worst miss you can. Then take an infra red heat gun and shoot each cylinder at the exhaust manifold. If you have headers its works real well. Just look for a cylinder that is cooler than the rest. Its usually a good place to start.
If you do have a real miss you can try this. Adjust the curb idle screw to the worst miss you can. Then take an infra red heat gun and shoot each cylinder at the exhaust manifold. If you have headers its works real well. Just look for a cylinder that is cooler than the rest. Its usually a good place to start.
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Ok I left my brain in the shower, I understand keeping 5 and 7 apart but I'm lost on the ( cross w/x thing) do you mean cross one over another wire so they're not running side by side? Thanks ED
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Pro
Joined: Apr 2007
Posts: 736
Likes: 1
From: Chester VA
Given that you said you worked on the carb and that resulted in a change, I'd continue troubleshooting that. Your idea of a coil is an easy thing to rule out though, coils aren't much $. If the $ is a big deal, just try it and if it doesn't solve it return it.