BMX Dad

My datalog is posted at:

http://www.mediafire.com/view/h03gk1...P3S2129782.csv

I would greatly appreciate analysis of the data.

Car may be running rich - rotten egg smell from exhaust.

Thank you for your review and suggestions.

Injuneer

Got it. I'll take a look at it. Only DTC is 66 for the A/C pressure switch. Seems to be grossly over-fueled in low load cells, with the long term fuel corrections (LTFT) bottomed out at 108 on both sides. The MAF flow at idle looks to be on the high side, MAP is high at idle, but probably a result of the cam specs.

When you go WOT (PE mode) the LTFT's default to 128, as they should (PCM was subtracting fuel), and the left and right O2 sensor values to not seem out of line. Recognize that the stock narrow band sensors are not very accurate at the A/F ratios used for max power/torque at WOT, so there are no "absolutes", but in general, they don't look overly rich when being fueled with 128 LTFT's. That would seem to indicate the problem is focused on the low load operation - something that affects the A/F ratio more at low load than at high load.

You have a lot of knock retard in PE mode.

How old is the cat?

Who tuned it?

I'll continue to look at it .

As an aside, how do you like the JBA's? I had a set of those back in 1996 when my car was basically bolt-ons, and felt they really seemed to strangle the engine above 5,000 RPM.

BMX Dad

Fred,

Thank you for the review.

CAT is only two - three years old. Found a brand-new stock OEM CAT (single CAT Fed model) from a guy who bought it new and never installed it.

Tad Banzuelo in OC CA tuned it.

The JBAs are all I have ever owned so I have nothing to compare them to. I have had them for several years with no complaints. Tad says I would pick up another 60+hp if I switched to LTs.

Thanks again......Bob

Injuneer

Not sure that I have much to add to the above comments.

The following data looks OK:

-idle is stable at programmed RPM (800)

-IAC is in acceptable range at idle (38), and opens up with RPM as it should

-Coolant temp appears normal (194)

-Intake air temp appears normal (85 while driving, 94 at idle)

-System voltage is good, always above 13V

-Closed throttle TPS is in the acceptable rang (0.75V) and WOT as well (4.53V)

-MAF readings at idle are a little high... might be due to the tune/cam. Used to looking at 6 grams/sec, and you are running 10+ G/Sec. Could also be the result of mods to the MAF calibration table, or a problem with the MAF. The excess air flow at idle corresponds roughly with the PCM's efforts to reduce fuel.

-MAP slightly high at 46kPa, butnot out of line with the cam specs.

-Spark advance at idle, and even under load looks to be on the high side. The increased advance at idle may be the tuner's method of compensating for the cam.

-As noted, you have a lot of knock retard, but the worst incidents (6/7*) are experienced on lifting throttle. Any chance something is banging on the chassis when you let off the throttle?

-At idle, the PCM is pulling out 15% fuel on both sides, and another 15% using the short term fuel corrections on the left bank, for a total fuel reduction of 30%. The right side isn't quite as bad, but the long term corrections are bottomed out on both sides.

As noted above, the big problem is the high excess fuel at idle, and continuing on into the low load cells. By the time you get to the high load/high RPM cells, the problem
has virtually disappeared. In PE mode, defaulting to Cell 15 and LTFT's of 128, your O2 readings are not unreasonably high. Right side is generally just under 900mV, and the left side is generally just above 900mV, although it does reach 945mV on a couple of the WOT pulls. Read cautions above on the accuracy of narrow-band O2 sensors in PE mode.

I'd provide these comments to your tuner and see if he can think of reasons it would be running extremely rich at idle and in low load cells.

BMX Dad

Fred,

Wow! Thank you very much for taking the time to do a deep dive on my datalog. I will share this with my tuner.

Thanks again.......Bob

BMX Dad

My tuner, Tad Banzuelo, found that my left O2 sensor was not functioning. I replaced the wiring to the sensor and the O2 sensor.

Ran a new data log tonight. Car seems to be running strong and smooth.

Data log: https://www.mediafire.com/?c0k4u52t4zwj00o

Injuneer

Interesting, because in the data log you linked in your initial post, both O2 sensors were functioning normally in closed loop. In fact, if you take an average value of the left and right sensors over the 5,600+ lines in your log, the difference in the average millivolts is only 1%.

The only difference between the sensors seemed to be the time it took to reach operating temperature and start working. That could be indicative of a problem with the left O2 sensor heater circuit, but that would set a code, and none was present.