Engine missing and erratic spark.

[mpellis]

My 82 K10 with a 350 in it has developed a engine miss and has reduced power. On acceleration it even causes the truck to shake. When I first noticed the missing I checked the spark plug wires and noticed that one had contacted a header tube and melted through the insulation. I removed the distributor and visually inspected the cap and rotor. Each looked nearly new. I did find that the previous owner did a crappy job of splicing the battery wire connection at the distributor cap and fixed that. I replaced the spark plug wires but the miss did not go away. I bought a non invasive spark tester that you hold next to the wire and press a pocket clip and a light illuminates each time the wire passes current. I noticed that some cylinders the light seems to be illuminating almost twice as fast as others. The spark seems to be very erratic. Could the spark plug wire contacting the header have taken out some other component and cause the erratic spark in some wires? Any suggestions on things I should check? Thanks in advance.

[Blazin]

Electrical is not my strong point, but you didn't mention if you checked and / or replaced the plugs? I would start there. I have seen cap and rotor that look perfect and have issues from age etc. too.

[jays2w87]

I agree with Blazin
 Fluke makes a good stick tester, its not designed for auto use but it works. I would say if the plugs are good, gap is good, distributer is set right then find a clamp on tester . They are really accurate.
Or try to advance the timming and see if it steadys out.
You only have about 5-8 degrees of play . Pass that and the engine will quit.
I had a 94 K1500 with a 305 tbi, when I got it, it ran like crap!
All I did was clean the plugs, check the gap and set the timing. I didnt even put a timming light on it, I gave it about a 3 degee turn and it went from a slug to a tire burner. 

[Lt.Del]

Do you have a garage?  Put that joker in it and turn out the lights.  Start the engine and look under the hood....any lightning storms going on in there?  It'll point you in the right direction.

I guess you could do it in your driveway at night time as well.  Look carefully at dist. cap....if it is cracked, you'll see some blue electrical strikes around it.

I'd replace cap/coil/rotor/plugs anyway. They don't last forever.

[mpellis]

Thanks for the replies guys. As Blazin suggested I put new plugs in the truck. I also had O'rielly's test the ICM and it passed.  I advanced the timing a little and it smoothed out some and is more responsive on acceleration. The truck is running a little better but is still missing. When I changed the plugs the #2 plug was black and wet with oil so I'm assuming there is some sort of mechanical failure going on there. I haven't noticed any smoking but haven't followed myself in the truck lately. My brother-in-law was over and when I idled the truck up to between 1500 and 2000 rpms he said the passenger side exhaust sounded funny. It doesn't feel as smooth as the driver side exhaust. The passenger side is where I had a ticking lifter earlier this spring/summer. Would a bad cam and lifters cause oil on the spark plug or is it a sign of something else. I am thinking about changing the cam and lifters.

[Lt.Del]

i dont think that would be causing the miss.  but i may be wrong.  I would still look at distr cap/rotor + coil.
New plug wires yet?

I am suprised that particular spark plug w/ oil isnt fouling up.

[Captkaos]

A bad cam would cause a miss.

[arkoza63]

the same thing hppened to just this week, burned a wire on the exhaust man. replaced wires helped some. just replaced plugs back to norm. replace the plugs.

[Blazin]

If one of the contacts in the cap is screwed up it would cause that plug to not fire. hence fouling out and a missfire. I agree it could be deeper like worn ring. A burnt valve could cause a missfire type sound in the exhaust. A completely shot valve seal could cause the oily plug. I agree that a bad cam would cause a mis fire but usually a bad cam gives a pretty harsh popping back through the carb. the more RPMs the worse it is. I would do a compression check. If you get a low number or numbers there than do a leak down test. If you run it without the valve cover on you might see a rocker that is not lifting as much as the others. Could be a bad valve spring or bent push rod?

[VileZambonie]

If it was the cam you'd see it on your vacuum gauge. Or as Blazin suggested idle with the v/c off and observe the rocker arms. If it's a simple miss just tune it up and gap the plugs.

[mpellis]

Thanks for all of your replies guys. Well the verdict is in. I took my truck to the mechanic I use and he put the truck on his scope. He found low compression in the #2 cylinder. After closing both valves the compression was good. He checked the cam lobes with a dial indicator and the cam is good. I have a bad lifter for this cylinder. Now I am debating whether to spend the cash to have him change the lifters or attempt it myself. The bill for diagnosis and changing the lifters will be right at $500 according to his estimate. It may be worth it rather than the hassle of trying to do it myself although I don't think it is a difficult job.

[VileZambonie]

Do you mean he did a cylinder leakage test? Is the lifter making noise?

[Blazin]

If you are going to do lifters I would do a cam and timming chain too.

[mpellis]

Vile, there were lifters making noise on the passenger side earlier this spring after I bought the truck. I took it to a mechanic to have the lifters adjusted and the noise went away. It appears that he may have adjusted them too tight.

Blazin, looks like I'll be doing a cam and timing change for sure. the rearward lobe on the #2 cylinder was rounded off as was the front lobe on the #8 cylinder. The rest showed some slight wear. When I saw the lifter from the #2 cylinder was parabolic shaped on the bottom.

The bad cam was a Comp Cams 12-238-2 and it is being replaced with a Melling MTC-1. I don't know anything about cam specs but hopefully the new one give me decent power and fuel economy.
The rest of the motor looks like it has the 10,000 miles on it that it is supposed to have. I should have the truck back by Tuesday. I can't wait to take it for a spin. My Eagle Talon is OK but I miss my truck.

[VileZambonie]

the MTC-1 is ok for a stock engine.