96 surges and misfire

[jwokmuba2]

i have changed spark plugs, wires, fuel filter, cap and rotor, cleaned exhaust tubing.

starts fine then surges to the point of almost stalling. also when driving it has a hard miss and stuttering problem.

before the cap and rotor change i checked the spark with a timing light and the number 1 and 2 wires were missing, so i changed the cap and rotor and checked them again, now the number 1 wire is missing, and the number 2 wire is double firing. which i think is weird, please help this is my only transportation.........

[old_master]

What brand and part number spark plugs are you using?

Is the cap wired correctly?

[CJ0717]

Hate to say it but the distributer caps on these are terrible. Same with the spark plug wires. I went through 2 brand new caps over the last 40,000 miles. Also don't but the cheap spark plug wires. This engine needs a hot spark to run properly or it will mis-fire continuously and randomly. The cheap wire kits run about $40. The goo wire kits run around $80-100 depending where you go. Also make sure the wires stay isolated from each other as much as possible. i.e. you don't want them crossing each other. Poor wires are not insulated well enough. I installed a cheap set once and had to go back a do it over again with a proper set.

[old_master]

Originally Posted by CJ0717

Hate to say it but the distributer caps on these are terrible. I went through 2 brand new caps over the last 40,000 miles.

I agree, caps are not something to cut corners on to save a couple of bucks. I'm surprised you got 40,000 miles! Install an AC Delco cap and put silicone dielectric on all terminals inside and out. It will last 100,000 miles, no problem!

[jwokmuba2]

yes the cap is wired correct, i double checked a few times. the cap is a masterpro and i dont remember the brand of plugs and wires, but being me there probably the cheaper brand..... i talked t a friend of mine who is a 30 year gm tranny tech.... not an expert on this specific subject.... he said it could be the distributer it self. something about the rotor that presses on the shaft can crack or break..... is that possible...


another symptom is that if i were to get on the highway and floor the throttle it will take off like a rocket. never miss a lick...???

[old_master]

Distributor bushings are known to wear and cause problems... remove the cap and check if you can move the rotor side to side, (radial play) if so, replace the distributor. As far as secondary ignition parts, (distributor cap, rotor, plug wires, plugs and ignition coil) you get what you pay for, just because it's new, is NO guarantee that it's good and it will perform properly. Secondary ignition is not the place to cut corners trying to save a couple of bucks. These 4.3L engines perform best when using AC Delco, stay away from aftermarket house brands, (Master Pro, Duralast, BWD, etc). Make sure the spark plugs are AC Delco 41-993 with a gap of .060 VERY important! AC Delco distributor cap D328A and put a dab of silicone dielectric grease on all terminals inside and out. Post your results.

[CJ0717]

I totally agree on this one. The 4.3L is a finicky engine. Very spark sensative. OEM replacement wires run about $100/set. The cap is about $60.
It will throw a random misfire code continually until you get the best parts on it.
Lastly is the advice from "old master" dielectric grease on the contacts in and out on the cap is the ticket.
Last note here. I used to work at GM Powertrain and we built the 4.3L Vortec for many years. It has an inherent misfire right from the factory. Very spark sensitive. Any compromise will cause the misfire to get worse and throw a code.