Ananta1369

1993 Camaro z28 LT1 always has strong exhaust fumes. If I'm sitting at a red light with my windows rolled down I feel like I'm going to pass out!

I have just completed my first scans of the car using Scan9495. Before I make any changes I would like to have these reviewed by the resident experts. Currently the car has Pacesetter long tube headers and the EGR delete mod and cat delete. Other than that it is stock.

I have the Fastbird O2 harness and two new A/C Delco 4-wire O2's but have not installed yet.

Also, these three scans are all done with the car in Park. I just finished replace the front and rear suspension but haven't gotten the alignment done yet.

The graph is the O2 sensor w/ LTFT data with the top for bank 1.

Thank you.

Injuneer

I'll take a look, but may take a day or two to look in detail, but the graph and the three files contradict each other.

Still using the stock 93 1-wire unheated. Just looking at the graph, the Bank 1 O2 sensor does not appear to be working. Bank 2 sensor is working, although limited range.Then I take a quick look at all three files and neither O2 sensor has moved off of ~457mV, indicating they are both not working.

Where did the graph come from?

Ananta1369

Thank you, Injuneer. Still using the stock 93 1-wire setup. I have the heated O2 conversion kit from FastBird that I will install. I wanted to get a baseline reading first to confirm my theory that the stock O2s are causing my issue. The graph is from the same scan94/95 software I used to create the scan files. As a matter of fact it was created the same time the third scan was done...2ndWarmStart.

Injuneer

Looking in detail at "2ndWarmStart", the Bank 2 graph turns out to be very misleading. The width of the lines makes it look like the system is spending an appreciable amount of time outside the limits of 400-500mV. But in fact, each line outside those limits is a single frame of data, occurring once in a period ranging from once every 10 to 30 seconds. It's not going into closed loop because of the Bank 1 O2 sensor problem. So it's possible that the ECM is making a perfect calculation of the injector pulse width, and hence the O2 readings are not moving too far from 450mV (14.7:1) target A/F ratio. But would be unusual.

Best thing to do is install the heated O2 sensors and see if things improve. Yes, check from a cold start. That will tell you if the O2's are working. See if it goes into closed loop at about the 206-second mark. Then you can learn more about why it smells so rich. The injector pulse widths are typically at ~4.2mSec, and that seems high. I would expect them to be at the 2 to 3 mSec range. Stock injectors? Stock tune? but if it was really running very rich, the O2 sensor readings should be up in the 700-900mV range.

Seems to idle 25 to 50 RPM above the programmed idle speed of 650 RPM in neutral. The IAC counts are too low at idle (6). Should be in the range of 20 to 40 to give the ECM more range for controlling the idle. On the other hand, TPS closed throttle volts (0.65V) are typical of a stock, unmolested throttle body.

Barometer (103.7kPA) would appear to indicate you are located near sea level. MAP is very good at 31.7 kPA, not showing any indication of misfires. Spark advance is where it's supposed to be at idle, and there is no knock retard, although none is expected at idle.

System voltage is good at 13+ V, except when cranking, where it drops to 8.7V. Healthy alternator, not so healthy battery ? ? ?

Engine really heats up at idle. What was the air temp when you were running the data log? IAT is 108-degF, probably heat soaked. But coolant is all the way up to 227-degF, which should turn on fan #1 (turns on at 226*F) but fan is not commanded on. That's on the high side for idle, unless ambient air temp was very high.

Ananta1369

You are correct, I live about a .5 mile from the coast. And as for the battery it will need to be replaced soon. Yes to both stock injectors and tune.

So I just completed the Fastbird O2 swap for the heated O2's. I completed another scan and you can definitely see the difference. Still seems to be running on the rich side. I am uploading the file along with a new chart which is much more active then the one from last weekend. Here are the details:

Scanned from cold start right after installing O2's. Outside temp around 75.

Thank you!

Injuneer

I'll take a look as soon as I can, but a bit backlogged. Seems much better from the graph. Into closed loop right at ~206 seconds, good sensor activity.

Ananta1369

Thank you. I really appreciate what you do for us on this forum!

Injuneer

The data log was started after the ECM had been reset (LTFT's start at 128). Operation was limited to sitting still at idle. That means the only A/F feedback is for Cell 16, the idle cell.

Take 210 seconds to enter closed loop, and the coolant temp is 136deg-F

Looking ONLY at Cell 16 (Idle)

The left Bank (Bank 1 - 1/3/5/7) appears to be functioning fairly normally. In open loop, the O2 sensor warms up, moves away from ~450mV, and drops a bit as it warms up, and the AIR pump is shown as running. Does not lean out as far as I would expect with a fully functioning AIR pump (but then you indicate it has been deleted). But is does drop to 300-400mV. When the ECM indicates the AIR pump shuts off (133 seconds), it returns to about 500-650mV... slightly rich. While you indicate the AIR is deleted, there is definitely a hazy connection between the O2 sensor readings, and the ECM flag that indicates the AIR pump has been activated. On entering closed loop, the O2 starts to cycle. The STFT drops down to 120, where it starts to drop the LTFT to lean it out a bit. It drops as low as 115, then starts to increase. By the end of the log, the LTFT for Bank 1 is 122. But it has moved all over the place. That means at the end, seemingly stable, the ECM is pulling out about 4.7% excess fuel to keep it at 14.7:1. To me, that's within an acceptable range (+/- 5%). But there was a period when it was pulling out 10.2%.


Right side (Bank 2 - 2/4/6/8) not so good. With the AIR running, it's way up at 820mV. Should drop well below 450mV with AIR running. When the AIR pump shuts off, increases to 860mV. By the time the system enters closed loop, it's all the way up to 930mV. That's really rich. In closed loop, in response, the STFT nose dives to 96, pulling the LTFT down to 123 almost immediately. Hovers there for a while, at this point, not much different than Bank 1. Then with both banks continuing to drop. The Left bank LTFT reaches 115 and the right bank bottoms out at 108. That is as low as it can go, pulling out 15.6% of the fuel.

At this point, things change.... Left bank starts raising the LTFT rapidly, and the right bank increases, but not as fast or as far. Really weird.... it's like something happens, the O2 sensors, particularly the right side, are hanging down in the 100-200mV range for an unreasonably long period of time. Then things flip again, and the Left bank LTFT climbs to 137. Then is starts to drop again.

Please confirm you were not moving the throttle. The TPS stays steady at 0.65V (0%) for the entire log. BUT - MAP is changing and the ECM starts changing the LTFT's. The MAP seems to run mostly in the 32-33kPa range, but when all of a sudden both banks start to rapidly raise the LTFT, MAP is steady at 38-39kPa. MAP should not change at idle unless the throttle moves. Misfire? Hanging valve? There are other places where the MAP suddenly jumps up above 40kPa, then suddenly drops below 23kPa. Faulty MAP sensor? These are not normal changes. 1993 runs in speed-density. MAP is a key input to the calculation of mass air flow into the engine, hence the ECM bases fuel injector pulse width on MAP (and IAT).

MAP goes up, ECM starts raising the LTFT, MAP goes down, ECM starts lowering the LTFT. Has to be connected.

What can cause a rich condition:

Things that affect both banks:
- high fuel pressure
- fuel contamination
- canister purge (doesn't happen at idle)
- MAP lower than normal
- intermittent TPS sensor
- EGR open at idle (shouldn't be, and you indicate yours is deleted)

Thngs that most likely affect only one bank:
- rich injector
- leaking injector
- leaking fuel pressure regulator (dumps into vacuum port on Bank 2 side of intake)
- misfires (causes a false lean reading)
- leaks in exhaust before O2 sensor (causes a false lean reading)

Sounds like there is something affecting both banks of the engine, most lilely related to MAP, and also something affecting Bank 2.