Has anyone ever had surging and/or slight bucking during cruising at say 47-53 mph at about 1700-2000 rpms. Where your not giving it any gas pedal or just barley. I've cleaned my MAF, throttle body, TPS, and IAC. I also tried to reset my TPS, and my IAC but I still have this problem. I was getting this at really low speeds of about 25-30 mph. But after I cleaned and reset the TPS, IAC, MAF, and throttle body it seems to have gone away at the low speeds. I have a modified 383 TPI with a rebuilt 700r4 Pro built trans, with a Big end 3000 stall converter.
Any suggestions/ideas would be appreciated.

 

I had something very similar. Turned out to be the distributor. I'd check the entire ignition.

 

Distributor!
I don't think I would have considered that. I have a MSD Ignition system. What do you have or did have at the time, and how did you you determine that was it?

 

Funny that you mention the MSD ignition. I've heard that by adding MSD style ignitions, you can really strain old ignition components. ....and that would make sense. ..Within a few hundred miles of going to the MSD 6a and Blaster coil, I started having minor issues. It felt just like an occasional miss or a skip, like a bad plug, so I did all new plugs, wires, cap and module. That didn't work, so I went with a new distributor. By the time I did the dizzy, ( a few weeks later) I could feel it the miss just about everywhere I went, and when it was replaced, it was instantly silky smooth! It's not a bad idea to have all new ignition components, so I didn't mind the trial and error approach. I've also heard that ignition modules can be brand new, and not work right, so if you DO end up getting a new ignition module as well, spend the money and get the AC delco, not the foreign knock off.

...as for how I knew is was the distributor, all I can say is that to me it just felt like an ignition problem. Took replacing everything to find the distributor as the problem!!!!

 

Thanks for the info.
I have all MSD ignition components even my wires. I even paid the few extra bucks and got the better MSD coil as I went through 3 MSD stock replacement coils and they all crapped out on me in 6 months or less. The ignition module in my MSD dizzy is the one it came with, should I try and replace it with the AC DELCO?
The one thing that does seem different than your situation is I don't notice any misses just the surging hunting almost at light throttle at 47-53 mph. Other than that it seems to run fine. Although sometimes I notice a little backfire which seems to occur when I punch it at 1/4 - 1/2 throttle, but not all the time.

 

Without really being in your car, there's no way to feel what you're feeling. If you already have a new distributor, i'd say it's less likely to be the culprit than my situation, which may very well have been the original dizzy.

...it may very well be the tune. Who tuned it? Surging and hunting sounds like tunes and sensors. The more we discuss, the more I'm leaning away from it being your ignition.

...however, how about this? could your surging/hunting actually be your torque converter locking and unlocking? 3000 seems kinda high for a TPI car, especially a big inch TPI like your 383. At lower RPMs, your TC will still wanna lock up, BUT...you may be under your stall speed, causing it to lock and unlock, lock and unlock. P.I.T.A, trust me! Ask me how I know! LOL!!! ....can you make it surge/hunt whenever you want? If so, just rest your left foot on the brake ever so slightly. It'll be enough to keep the TC from locking. If that helps, there's your issue. I had the same thing.

 

Your not the first person to suggest the converter. I had thought and was even told though for my cam a 3000 is the way to go. I guess I'll look more into that, but to talk to someone who really knows about converters can be difficult as it seems to be a bit of a mystery. Or one person says one thing, and someone else says something else and they both claim to be experts.

 

We're talking two different things. As for your surging/hunting issue, it could possibly be the locking and unlocking. Even if your engine and converter were perfectly matched, this could still be an issue. I wired in a switch to the brake switch, so while driving aggressively, it fools the converter into thinking the brakes are being applied, and it won't lock up. Flip the switch for normal driving and it behaves like normal.

....but as for whether or not the converter is too large... it might be a perfect match for you cam. That's not my point. My point is that both the cam AND the converter might be too big for your engine. On a stock 350, the TPI doesn't flow real well, and has a low RPM operating range. On an air hungry 383 like you have, it's even worse! The power comes on lower, but doesn't last long. On my 350, I had a 2400 stall, and that's where the power really started to come on. By pure physics, you're making power even lower, but your converter is wasting it until 3000. ...then probably about 1800 RPMs later, the TPI runs outta breath. I don't know what cam you have now, but as a rule of thumb, you want a shorter duration with a TPI. Get more air through more lift, not duration. ...then of course, you want to match the converter to whatever cam you have. Of course, it'd be cheaper to leave the cam and converter, and change your intake to a stealth ram or FIRST system.