90 straight six, manual. Fuel filter. Iac/tps throttle body all cleaned and properly adjusted. Still getting a stutter under load, but not while accelerating. It's almost like the injector pulse is off. I still need to double check the dizzy but if it was off I feel it would be a constant issue. For example- if I climb a hill in 2nd and hold the rpms at about 2500 let's say, it will buck and stutter. If I try the same hill in 3rd gear (let's assume I can make it up the hill) and I give it 50% throttle, no stutter, makes it up the hill just fine. I'm pretty lost on this one, tune up was done a little under a month ago

 

Also, grounds have been refreshed, as well as a 4 ga solid copper ground added to the upper rad support

 

I'm pretty cheap...I'll gap my plugs a couple times between changes. (the gap get's a small tad bigger every mile). (.035 Is the spec Btw.). Also if all looks OK, I'll clean the cap and rotor, sometimes the wires, right in the kitchen sink with dish soap. Anything on/in the cap can give the spark somewhere else to go other than to the plug. Be sure all is good and dry.

Also these things don't like Platinum plugs for some reason. Do you have a gauge? It's running at around 200*?

 

Does heat make a difference? Mine did that until I added a switch for the efan. It's much better now. Never really did it in the winter.

 

Ok, it has champions gapped at 35, cap and rotor are clean, it runs right about 200 per spec, and the fuel is just regular old 87 with a bottle of seafoam.

 

By champions I do mean the coppers

 

OK, so plugs are cool. For us following, under load, is more or less the same as accelerating to me.

"Buck and stutter" climbing in second......Good one! (In the old days a fuel delivery issue, simply the vertical from the tank up to the bowl could show up on a steep hill!).

Does it ever do it level? Got around one ohm resistance between the engine and battery neg? (I know you did stuff, but maybe check it?) Stranger things have happened.

I'd check/clean the dizzy cap.

 

Yes, level ground, uphill, downhill, regardless, it happens. Check resistance, 0 ohms between terminal and block.to clarify what I mean by under load, I mean if you were trying to maintain speed/rpm, it does this. If you were just accelerating, it runs fine.

 

Have you looked at the connectors inside your spark plug boots? I was experiencing the exact same thing and discovered an arcing issue on one of my plug wires. Interestingly, it rarely (if ever) seemed to stutter when I was accelerating, only when maintaining a constant speed. Something to consider.

This is what it looked like under the boot on my #4 plug wire...

 

I will have to look into that...very interesting

 

Parsnip, don't ignore the dizzy indexing.

Things wear with time, and if it was indexed improperly when new and on the ragged edge, it could be out of spec now. What you're describing is one of the symptoms of a mis-indexed dizzy.

The issue comes about because the ECU tells the coil when to fire.

The dizzy, if mis-indexed, could get fire when the rotor is too far from the cap terminal when the firing happens. Has to jump a huge gap.

 

I'm going to do that riight now, but quick question on it- the trailing edge of the dizzy should be on the #1 cap point at tdc, correct?

 

Note from DJ
Go to cruiser54 #12 & 13

 

There's photos in the post. Trailing edge of the ROTOR.

 

It's the trailing edge so when the ECU advances the spark, it can still reach the electrode on the cap.