Stumbling when taking off in....

[Ben]

84 full size K5. 350, manual transmission. Driving in 1st gear is fine. Shift to second and if I step on it just a little, it stumbles until I get going faster. Same with 3rd gear. Stumbles. Cruising speed, step on it and it'll stumble until I get moving faster then it idles out. Timing is 4 degrees. New wires, cap and rotor are on the way. For now, the cap, rotor and wires have to do. They are three years old. I did remove the cap and rotor and sanded down the carbon off the metal tips. Still stumbles. Carb seems OK. Starts up in the morning fine, chokes seems to be working fine also. Ideas? Thanks!

 

[1989k5]

In my experience, I consider either fuel problem or electrical if electrical I tend to start with the plugs, then work my may back to the more complicated. If you said the wires etc were three years old, they should be good unless they appear burned or cut. Check your plugs first to see if any of them appear wet or sooty, that may indicate a cylinder is not firing for some reason. If you isolate the prolem to one cylinder, try replacing the spark plug, then wire. If all plugs look ok, check the cap/rotar. The other thing to consider is your timing. Make sure you are disconnecting the vacuum advance before setting the timing. That can be a pretty common mistake. I believe your vehicle is an 84, I don't remember what ignition system it has, but if there is a vacuum attached to the side of the distributer, that is where the vaccum hose is to disconnect. If you have a ECM, the wire to disconnect would be in front of the brake master cylinder on the drivers side firewall. Usually brown and outside of the wiring harness loom. I'm not sure if this helps you or not, you may have done these checks already, but it is a place to start. Good luck.
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[1badv10]

i had a similar problem would run rough at low rpms but idled fine, if you kept it in lower gears and out of overdrive it was fairly smooth /forums/images/graemlins/thinking.gif .. turned out to be a wire burnt to the underside of the header pipe.. found it by using a heat probe on a multimeter and checked the temp of each header tube while it was running.. found 1 tube 50-75 degrees cooler went from there.. hope this helps.. patrick