I've had this problem for a very long time.
Due to the cam and various other factors it is not noticeable.
I suffer no tremendous power loss that I've seen in WOT, so I think its a closed loop issue.

It is most noticeable in 3rd or 4th gear from 1600-2100 RPM (35-45 or 55-65mph
And literally feels as though I am going over rough road, shaking the vehicle.
I have all my power at partial or WOT it seems, I don't notice it unless I'm really looking for it as RPM's increase above 2300. It's as though one cylinder is randomly not firing.
I've replaced the opti recently, and the coil, no change.
I have installed and programmed in 36Lbs Ford SVO injectors, it has not made the problem worse or better. I have full pressure at the regulator.

I'm sure this is a problem many have come across... this issue has been around since 4-5 years ago after the original baseline PCM4Less tune was programmed in.

Thoughts? Need clarification?

 

bump for lack of a response.
I have datalogged and it looks completely normal to me. if someone wants to take a look at one.
For some reason timing is being pulled a maximum of 5 degree's.... this isn't always the case, notice that its not going down, nor is any knocking being detected....bad gas maybe... but the vehicle was stuttering during this run.

http://myfreefilehosting.com/f/aaae3e8a79_0.05MB

here's another example, just prior to that one, where there is no timing being puled, same rpm, same stuttering.

http://myfreefilehosting.com/f/df96a038ed_0.12MB

 

bump for lack of response after 2+ weeks

 

Almost sounds like converter lock up clutch chatter.

 

possible, depending on what converter lockup chatter is. its happened on the old converter, and the new one, and occurs throughout the powerband, not just before, during, or after the converter's lockup speeds (which I know, because I set them all). I also firmly feel the converter locking when it does right when its supposed too.

 

So for the lack of response. It really sounds like the torque converter, I had mine changed out twice. However, if you have check this out, then its anybody's best guess. GL

 

I kept thinking I had put this information in, but I guess I never did.

This never happens unless in closed loop... so, for the first few minutes I drive, longer if its cold, and the PCM is showing its in open loop, I try to replicate the results, and I can't, it runs smooth as silk

Tranny and converter tables don't differ between closed and open loop for the lockup... hence this cannot be a lockup issue and is a fuel/air issue... timing isn't moving, and it seems as though A/F is fine....
what about the pulse width table on the injectors... or something else... I cannot believe I'm the only one suffering from this issue.

 

Converter won't lock up until the either the coolant temp or transmission fluid temp reaches a certain temp. That would explain why it appears to not do it until it is in closed loop. I had a Yank ST 3500 in a 98 Z LS1 that had lockup clutch chatter. Best I can describe it is do you know those strips they put in the road that allert you when approaching a toll booth? Felt just like running over those. Only did it on light acceleration between 40 and 60 mph. Sent the converter back to Yank and they said they could find nothing wrong. I put that converter in two other cars after getting it back from Yank and it did it in all three cars it was in.
Next time it is doing it, lightly apply the brakes while acceleration. That should unlock the converter and see if it stops.

 

New response to an old post. My converter does the same thing. In OD on the highway is where it's most noticeable. You feather the throttle a little and it does it. I can see it's locked up by watching the tach.
Let up on the throttle and give it a little more agressive tap, the converter 'unlocks' and no chatter... more like a very hard chattering rumble. Step on the brake, converter unlocks, all is well.

I was wondering if there is an adjustment for this? A programming issue? Throttle cable adjustment? Throttle Position Sensor issue? Or... is the problem really the converter?

 

"Next time it is doing it, lightly apply the brakes while acceleration. That should unlock the converter and see if it stops."

Applying the brakes will unlock the converter... and unlocking the coverter is like landing on a trampoline (or actually 100ft of feathers) vs concrete (if converter is locked).. you wont feel the blow (or result) of a weak or misfiring cylinder with unlocked converter.

Make a stictly OPEN LOOP tune and see if it acts the same but make sure your converter is locked.

This problem is much more noticed in manual trans cars with cams since you dont have a torque converter "absorbing" the blow...
What your seeing is likely bank to bank fueling differences or cam reversion affects.. I see this at real low (but not lugging) rpm and load.. in my case it's usually just under 1500rpms and very slight accel (not cam surge). Seems to also only happen in CLosed Loop.. and since Im in SD mode it seems to change/disapeer depending on the tune but Im not concerned yet.

Reason I say it's Bank to Bank misfire (right side is making more overall hp than left side) is because it feels like more than one cylinder and feathering does make it temporarily change..

THere is also the other factor which I've always wondered about the SBC... any motor I've had other than the V8, when you "lug" the motor you can usually "feel" eacy cylinder fire evently.. the SBC is the only one that never "lugged" smoothly.. this is because the 4/7 cylinders fire at the same time which will give you a slight CHUG or general unsmooth "lug" unlike "lugging" even fire motors. Yea ok just lost a bunch of people there im sure.

Anyway to sum it up I think fueling control has the biggest affect on this. (one bank at 15.0AFR and the other at 14.0AFR = ~14.5AFR) but most importantly = different power output from each bank. OPEN LOOP USUALLY RESULTS IN THE MOST EVEN POWER OUTPUT FROM BANK TO BANK.