RobsWS6

I finally changed the original fuel filter and O2 sensors, all with 67K miles. All looked like they should except a little color(dirt) coming out of the filter.

I've been running OLSD for over a year and the car is really running pretty good. Would like to get a tad better gas mileage out of it as its about 20-21mpg mixed. Back in 98 when I changed the cam, I was getting 23-25mpg mixed.

So I'm going to throw it back in closed loop and start scanning again. I'm wondering if the VE will really change with brand new sensors and filter. We shall see. Hopefully the weather will cooperate and I can get this done relatively quick. Just need all this rain out of here.

I'll update whenever I do get out with the car to see what, if any, changes I'll be making.

bobdec

Once you go to CL-SD your O2's are going to start tweaking the AFR if your VE tables are not doing what the manufacture (O2's are looking for 14.7:1 stoich). So it all depends on what your current OL-SD AFR readings in various driving conditions are. I your car was happy w/o O2 correction, maybe getting them back in the picture could disappoint. I am currently CL-MAF and thinking about trying CL-SD as an experiment just to see if there is really any difference. Never considered OL-SD or OL-MAF as it opens up exposure to undetected sensor failures EG: MAP goes flaky w/o PCM correcting causing a lean mix !!. However in reality OL is the only way to have total control w/o PCM intervention and it seems having a wideband would be a requirement to see what's going on. Keep us updated..

RobsWS6

The VE was pretty much spot on when I finally went open loop. But that was with the old O2 sensors. I'm thinking they will need to be tweaked a little but not much. Unless it was really skewed because of bad sensors. It does run very well right now, so its more of a curiousity than anything else.

And like you said, gets the computer back in the game for adjusting things.

RobsWS6

Was able to get a first scan done today. Looked pretty good. BLM's in the -4 to +2 range. So just a slight VE tuning should take care of it.

I'm still getting this light bucking/surging in very light to no throttle at low speeds. This is basically why I went with OLSD and it got rid of it. I'm wondering if its DFCO screwing it up? Car is still running great everywhere else but this drives me crazy. It almost sounds like the driveshaft will come out of the car, like it has slack in the drivetrain.

Can anybody lead me in the a good setting for DFCO?

bobdec

Need more info.. you mention BLM's that sounds like OBD1, However '96 s/b OBD2 they call them trims, have you converted. Also since DFCO is effected by MAP any mods like a cam can change DFCO activation/deactivation. DFCO activates at 23 Kpa and over 1350 RPM and over 18 MPH w/a cam you may never hit 23 Kpa. Also the M6 code has a 1 second DFCO activation delay where the A4 does not have any delay what is your transmission setup ? If you are OBD1 then Datamaster/Freescan log should show injector BPW at 0 (zero) during DFCO, (BPW never goes to 0 in any other condition). As far as low acceleration hesitation, could be cam surge or timing related. In a data log take a look at your timing switching in TPS closed table and make sure as TPS moves from closed table to main timing table at lower RPM and MAP cells there is no dramatic jump in the timing. Also look at your RPM when coasting the IAC throttle follower table should keep RPM's up around 1100-1200 when coasting over 12 MPH and then return to idle speed as you coast below 5 MPH, that helps reduce jerking during low speed accell/decell conditions. Is this a CL only problem or has it been around in OL also ? Sorry for all the questions, but it helps isolate things.. Lastly it could be your universals, getting under there an manually checking for slop..

RobsWS6

Yes, running a 95 computer. After logging some today and looking over it, it isn't DFCO causing the bucking. It is already out of DFCO by then. I've played with the throttle follower for a long time prior and that never helped either. Definitely not u-joints as I just swapped back to my carbon fibre shaft from the 1LE.

This is only a closed loop issue and never a problem with open loop. I can be cruising around the neighborhood in open loop loving life and as soon as it goes into closed loop, bam...there it is. 16-1700+ rpm and it drives like a stocker, just low speed stuff is a killer.

So I've modified the VE very little since doing this as it was still pretty much spot on. I put it back in open loop and all is well with the world. I guess I'll keep trying to read up on LT1 tuning. Tuning my GTO was simple compared to this car and I have a much bigger cam in that car.

Ricardo

Rob:
I know this is somewhat old, but maybe you found the cure for it already.
Were you able to get rid of the light throttle bucking in CL or did you jst give up and run OL?

RobsWS6

Nope, just running OL. Its running very well and returning good gas mileage also. 600 mile trip netted 25mpg at about 75mph. Wish I could have gotten the CL to work but doesn't really bother me since it is running so good.

Ricardo

I am running CL and did extensive logging/tuning till I decided it was good to go.
I run a custom cam by Lloyd very similar to the 503.

Still get a little bucking (very little) under very light throttle sometimes more than other times. Its not bad at all, if you know how to drive with the cam you can fool anyone riding along with you into believing you have no bucking.
I would love to be able to get rid of all the bucking in CL (all of it).
It would be cool to start a thread with the actions taken by all of us to minimize bucking in cammed cars.

My car runs fine in OL at a fixed 13.5 AFR.

RobsWS6

In OL, mine is pretty much 14.5-14.9 AFR. Probably why it still gives good MPG still.

I tried running rich and lean to get rid of it but just couldn't. If I keep it in a lower gear and have the RPM around 1800-2000 driving around town, it won't buch at all. But I like lugging the thing around 1000-1100. In OL, its smooth as glass.

I might tune the MAF again but I really like running in SD. It just has much better throttle response than running a MAF. I've had in 100 degree weather and down to upper 30's and it runs just like it was stock.