Murray

20hp on top off the X-pipe and EIS is definitely worthwhile. I think you posted a dyno chart a while back that had you at 288 rwhp. i wouldn't mind a number like that.

Thanks

jcorenman

I've been following this thread, feeling a bit frustrated because this sort of diagnosis is dead-easy with a Sharktuner, but Murray doesn't have one available. There are other ways to do some checks, like the 'scope checks outlined in the WSM, but that is also not so simple for most folks. The reality is that these cars are hard to diagnose without some sort of tools to find out what all those pesky electrons are doing.

Here's what I would do, with a Sharktuner: Load stock files (eliminate any variables), check RPM's to be sure the tach hasn't gone flaky, check AFR* and the O2-adjust signal at idle, to make sure that the basic mixture is OK (this eliminates MAF calibration as well as fuel-pressure and air leak questions). Then look at the ISV control signal, is it in the normal 45-55% range, and moving around a little? Or is it at a higher value and calling for more RPM? (It should be, at 600 rpm). Then disable auto-ISV and manually step the ISV control-signal from 45% to 75% and see if there is a corresponding change in engine RPM-- this will verify that the ISV valve itself is working properly. And also check the EZK, make sure that the knock and hall sensors are all working and timing is not getting retarded. Somewhere in there should be the answer, or at least some pretty good clues.

(* Checking AFR requires a WBO2, but even without that the O2-adjust signal will provide a good indication of fueling. This is the signal that the LH generates in response to the NBO2 sensor, to adjust the AFR to 14.7. If O2-adjust wanders between -5% and +5% or thereabouts then the fueling is correct).

The fact that this problem first showed up with the AA chips is probably coincidental, the fact that the idle is less stable with AA chips is interesting, and suggests a fueling issue.

Remember that Autothority chips were done a long time ago, and there is no evidence that the folks who did them really understood how the LH and EZK work.
AA chips are '88 files with the following changes:

• Higher idle speed (775 vs 675), not needed for an S4 and not what an auto wants;
• More fuel in the mid/high-load range, where the S4 already has too much fuel;
• Higher rev-limit, not useful for an S4 and can't get there with an auto (and not a good idea if it could);
• And more ignition advance throughout the mid-to-high load "cruise" map.

The extra fuel is worse than useless, the S4 maps already have too much at the high end. So this likely costs top-end hp.
And it may be related to why Murray's idle is less stable with the AA chips: as RPM drops the ISV opens (assuming the ISV is working), and load does likely get up into the mid-load areas of the map (at low RPM) where they added fuel.

The change that is most interesting is the added advance: Up to 12 degrees more advance in the mid-to-high load part of the "cruise" maps, primarily in the max-torque area, for the normal cat map and the Aus low-octane map, but not the normal no-cat map.

Certainly adding advance in the max-torque area will feel "peppier". But two things are interesting: One is that the auto knock-retard for the EZK is 9 degrees, so if the timing was "edgy" with stock maps then the AA chips are going to send it beyond what the EZK can control with knock-retard.
The other interesting thing is that they did NOT change the WOT map, or disable it. So if you put your foot in it (and the WOT throttle-switch is working), then the ignition timing is exactly stock.

OK, back to Sharktuner: Certainly Sharktuning a dead-stock car is worth some hp. Any factory tune needs to work with a range of production tolerances and is necessarily conservative-- leaving some hp on the table. By tuning for your specific set of parts you can pick up that extra power, but it is impossible to predict how much exactly, because each car is a bit different. And for the same reason, swapping one car's Sharktuned chips to another is not the best option. If you are going to do that, then grab the MAF also-- that is probably the source of greatest variation, as they age.

But generally, Sharktuning a completely stock motor is probably not the most cost-effective path. It's fun and good training, but doing the mod's first and then Sharktuning will compound the gains.

Cheers,

AO

Note to self: Jim C. has forgotten more about Sharktuning than I can ever hope to learn!

Murray

Hi Jim,

Thanks for the write up. I didn't really notice anything in terms of additional power at WOT. Mid-throttle did seem peppier, but I guess it's really no different than just stepping a little further on the gas.

Like you I find the frustating part is the difficulty in diagnosing things. Without a sharktuner and an experienced tuner to work through it with you, there just isn't any easy way to work through these kinds of things. I guess that's why you see so many threads of people replacing this that and the next thing trying sort it out.
I guess the onset of this symptom (low idle) and the AA chips is coincidental. I will try and resolve that issue as best I can. If I have to take it to my mechanic in the end so be it. Right now it's not currently causing any drivability issue. It idles smoothly, doesn't hunt and isn't stalling.
I do plan on adding the EIS to my X-pipe equipped car and will then see if there is a way to get it sharktuned.

AO

Hey Murray,

It's a long-shot, but if you and the boys are ever down my way, I have a full Shark-tuner setup complete with spare brains (PEMs installed), MAF, WBO2, etc. We could plug it in and see what happens. Scheduling the time is always the hard part. But you and I could work on the car while the kids get their fill of video games and what not. Anyway, letting you know it's an available option for you.

Murray

Thanks Andrew. I may very well take you up on that offer.

Murray

Can a vacuum leak cause a low idle or does it always cause a faster idle?

Speedtoys

Generally faster until its too big, then runs baaad.

Murray

That's what I figured. I did find a vacuum leak at front fuel dampener and there is still a whistle at idle that seems new. I'll have to chase those down but I doubt they are the cause of my low idle. I think I'll pull the plugs and see what they look like.