Which PIDs to scan?

[Garry]

Once I get my car on the road, I will need to figure out the cause of some hesitation in the range of 2550 and 2750 under light load & throttle .. someone on ls1.com already suggested I should be turning off the O2's and then do some scanning - which PIDs should I logg in order to narrow down on the cause of the problem? Same as listed in the VE tuning tutorial?

[emarkay]

Turn off the O2's???

What year, model, mods... ... ...

First eliminate any "old school" issues - air filter, fuel pressure, vacuum leaks, backpressure, bad plugs... ... ...

Hessitation can be fuel or spark, or totally mechanical, in which case you may not see a result directly on the scan. Give the car a good "tune up" and a good mechanical diagnostic check, and get back with results and above needed information.

[GMPX]

Well, hesitation or laziness can be either timing or fuel, as we always recommend, get a WBO2 to monitor true mixtures, certainly log timing, and as emarkay suggested, don't forget the mechanical basics.

Cheers,
Ross

[Garry]

LC1 is on the way, guess I should have it by next weekend ... will see how that turns out ...

[ringram]

Log spark timing, commanded afr, o2 mv both banks, Id break spark timing down further and log modifiers like burst knock etc. In fact quite a few guys zero out the burst knock tables as it pulls timing when you tip in throttle often for no reason. Just make sure you log actual KR if you do this and make sure you havnt opened yourself up to real knock.

Now strange as this may seem, I had a similar hesitation, stock PE can cause horrific AFR ratio's of 11:1 or worse. Now if you are driving at stoich, and suddenly trip PE mode into washing out your flame with 11:1 you will notice a slight bogging or hesitation. I changed to OS3 and ran fully commanded B3647 fuel map and it got rid of this issue as AFR was progressively richened rather than suddenly triggering for litte to no reason.


Another way to address this on a stock OS is to change/check the stock PE mode MAP trigger. Its normally 15kpa, so basically PE can be triggered at idle! Id change this to 80 or even 85kpa, so PE is only really triggered under load.

But yeah, as the other guys suggest a wideband will help you "see" the problem.

[Garry]

OK, here's the PID list I'm going to run some time this week ... can't find the spark timing PID you mentioned, though ...

[ringram]

burst knock is est_krb_dma total spark after all mods is est_run_dma and knock retard is plain old KR.

[Garry]

Thanks ... I removed the second bank of some of the values to get back into the 24 channel limit ...

[Garry]

just came back from the weekend at the track ... apart from realizing the clutch is starting to head south, I recon my problem with the hesitation might indeed be caused by SOMETHING with the O2 sensors - under load, especially WOT, HO2S11 is almost flatlining, while HO2S21 stays pretty active. Together with this, the motor goes to Open Loop, with AFR dropping to 11.70 ... Under small to no load, both O2 sensors are rather close to each other ...
I will be putting the car up on the lift and swap sensors - see if it's either a cable, or a sensor that causes the problem ... also got my LC1 today, so that is going in some time soon...
Btw, which side is the HO2S11 sensor?

[ringram]

Yep both should flatline at WOT, if only one is, something is wrong with the other one.
At part throttle they should flip from 0 to 1V all the time. Looks like something up with H02S21 might be where your KR comes from. Could be bad injector too. Definately swap sides with the sensor and see what you find. Do you have any DTC codes?

When you start tuning your ve in open loop you can forget about the O2 sensors for a while. Hell many never go back to using them.

If one is bad how about wiring your LC1 in that side and setting it up as NB for a replacement. Mind you it could also indicate an exhaust leak, dodgy injector or something on the side that stays active during WOT.