Cambridge205

I'm sure this is an easy problem for most of you to fix but I'm new to tuning so its hard for me to figure out. my car is an 89 GTA 5.7 with a ZZ4 cam. I'm using Turnerpro RT for data logging and bin editing. Heres the problem, I think when the car goes to idle in closed loop I'm getting a false lean because it smells like gas but I still get high BLM's, on start up and in open loop my blm's are at 128 but smells like gas...

When cruising around I still have high BLM's so I changed the injector constant to 19.7 and that really richened up the cruising part but it didn't help the idling part.

So I'm thinking I need to get less gas at idle but more at higher rpm's and I think the way to do that is with the MAF tables. Would it be ok to leave the lower constant and just change the MAF tables for the idle? Would I have to increase grams or decrees them in the MAF table? does the MAF table change the injector pulse width? Under volts in the MAF table is that how many volts the ecm is reading from the MAF?

Cambridge205

I just found something interesting when I was going for a drive yesterday and data logging about halfway in my cruise I started getting knock counts at a certain RPM I think it was about 2100 RPM and whenever the knocks happened I got some knock retard but once the knocks stopped the retard went back to 0. So I drove it home and in the carport I revved it to 2500 a few times and every time I did that it got some knock counts added and knock retard.

This morning I wanted to see if it would do that again and it didn't. I revved it in open loop and closed loop it wouldn't add knock counts. maybe it has to be driven for a while??

I'm running 91 octain for now. I heard low fuel pressure could cause this but my fuel pressure is 43 psi. The only changes to the PROM is manual tranny enabled, lowered the cooling fan temp, and lower injector constant. It has stock timing from the apyu-3561. When I had the higher injector constant this never happened but it ran real lean. But now its running almost stoich maybe a little on the rich side.

pandin

Something to try: $6E code Maf

Put 130 in your Max blm (04D4) and 140 in the Max integrator (044F), this will allow the car to run with out dumping a ton of fuel at idle. Check other BLM cells as this will limit (lean) any cell reading over 130.

This will also allow you to see when the issue changes (blm's drop).

Check and see if "BASE PULSE CLOSED LOOP CORRECTION, SCALED 1" is loaded in the ADS file. It is Bit 19 (bit 20 is BLM output) just insert and match all the other info. This is the "Fine correction", it goes up and down before the integrator does.

Do a idle data log (in park and no AC) and watch the O2 counts vs the fine, integrator, and blm values, if the O2 is reading low and the blm's are slowly climbing, go to the "Closed Loop Rich/Lean Threshold vs. Airflow table" (046B).

In the table there are Grs/sec vs O2 mv, find the match to your idle grs/sec, lower the mv number to something closer to what the O2 is reading, before it starts to climb as the blm increase. I graph in MS excel, then use Max, Min, Median, Avg, and Standard Deviation to find the middle.

To make this table "easier to read" add a copy of 046B and delete the math correction, this will then display in Decimal (nice even numbers). Also adjust the upper (0459) and lower (0462) keeping the same spacing (+ - 10 Dec).

This is what I am using to find the idle O2 threshold (mean), the cruise will be different. This is also where to adjust the Air pump offset out, if it has been removed.

"Diff Value to Make up Rich/Lean Window When Air diverted (VDC * 226) subtracted (0454)", this is where the 100 mv O2 offset is stored.

"Diff Value to Make up Rich/Lean Window for Fast O2 (VDC * 226)" (0453) is also a 50 mv O2 offset. These two constants can change the O2 mv center by 150 mv.

The upper, threshold, and lower tables are factory loaded higher. In ARAP $6E, the threshold table is factory loaded at 8 Grs/sec 611 mv.

Subtract 150 mv and you are at 461 mv, a little on the rich side of 445 mv (14.7) for idle.

It is my "opinion" that this is a better place to raise/lower idle fuel then the Maf tables.

I welcome any and all comments, this is how you learn something new.

Do a search on "O2 swing points", for more detailed discussion.