I think Im having some ignition problems in my 96 tahoe. Recently its been idling a little rough and misfires when the engine is loaded when accelerating. All plugs appear to look good - tan color and very clean and were regapped today. I've swapped through 2 sets of plug wires 2 caps and the rotor is new and appears to be in good condition. I used my digital timing light to read the rpm on each plug wire to see if I could detect the misfire at idle. All but 2 wires would vary between 580 and 650 rpm. The #3 and 5 cylinders would read between about 600 and 1200 rpm most of the time. This seemed odd. Since these wires are side by side in the distributor cap could I possibly have arcing between these 2 pickups in both of my caps? I dont see evidence of this under either cap or hear any ticking from the distributor area while idling. The wires dont appear to be the problem since Ive tried 2 sets. When I unplug either of these two wires it appears to idle better. This seems extremely odd since the plugs arent fouled. I havent checked the coil yet but dont think its the culprit. Anybody have any ideas?

spider injectors, intake gasket.

Just a thought.....Have you checked the pugs for fractures? I had the same problem and was getting ready to change out the fuel spider, then I checked the plugs really close and found one of them to be fractured. That fuel spider is $$$! good luck

I'd look at the cap and rotor. I have had a lot of trouble with my 97. There are two vents in the bottom of the distributor that MUST be cleaned out or you will go through caps and rotors in NO time flat. I'd check the cap and rotor really close, clean the vents and then swap in a new cap and rotor. I have seen this happen in probably 5 different trucks. I have also only had luck with the CSK lifetime warranty caps and rotors. NAPA ones didn't survive and neither did Standard Motor Products' offerings either. Good luck.

You must have a flashing check engine light ,right?if you don't ,then you don't have an ignition problem/misfire .But that said ,check the plugs for cracks or carbon tracking ,and if that is O.K. , spray some water on the plugs and wires you suspect ,that'll get their attention if they are leaking voltage.

The pcm senses "Real" misfires ,but not necessarily a mechanical "shaking".If you have a cam shaft /timing chain issue ,you can have a shake and a timing issue without having an ignition issue .

Also , check that the metal reluctor ring inside the distributor doesn't have a glob of metal filings on it between any of the high points and there is a reluctor ring inside the timing cover that can crack and cause erratic timing.

Your spider injectors also can stick open and send too much fuel into a cylinder .

If you can't find other cause ,I'd suspect mechanical prob between the cylinders .Those engines had shitty plastic intake gaskets that split and come apart ,causing vacuum leaks and coolant leaks .

Also , a blown head gasket between cyl 3 and 5 would cause most of your complaint and not necessarily use coolant at an early stage of damage.

If you can borrow a laser thermometer ,you take the temp of all the cylinders and watch the suspected cylinders ,if they are colder ,then they are misfiring ,if not ,then you have a shake ,not a misfire.

All this could easily be checked by a qualified mechanic in less the an hours charge .