Scanned The Z With My Laptop Yesterday - Here's What I Found...

[97LT1Z28]

I just got new scanning software yesterday - I'm still trying to find the low-rpm miss and rough idle problem. Here's what the program says:

At Idle in closed loop:

Manifold Absolute Pressure (in/hg) is 10.3 - 10.6
Intake Air Temp is 109 dg F
Ignition Timing Advance varied between 14 - 16 degrees
MAF Flow Rate was .86 - .89 lb/min
Long Term Fuel Trim Bank 1 was -7.8%
Long Term Fuel Trim Bank 2 was -2.3%
O2 Sensor B1S1 Voltage ranged from .12 V to .795 V
O2 Sensor B2S1 Voltage ranged from .08 V to .835 V

The Bank 1 and Bank 2 O2 Sensors didn't seem to follow one another - it seems like they each did their own thing separately.

Now I'm thinking my problem is both the front O2 sensors......

[Kevin - Blown 95 TA]

You might have an exhaust leak. I just went through this when fooling around with spark plugs which I had to remove the Y-pipe to get to #6. In removing the Y pipe twice & with the donut gaskets getting old, I ended up with an exhaust leak that was making my fuel trims add fuel. My car was running rough and idling poorly. I finally pulled the pipe back off and put new gaskets on there and that made it better but not as good as it should be. I retightened them once more, and the car responded with a smoother idle, better running, and better fuel trims. Not saying this is what's wrong with your car, but that's how a lot of fuel trims get messed up - intake or exhaust leaks causing faulty readings at the O2 sensors. At idle and part throttle, the O2 sensors just switch from rich to lean readings - they don't follow eachother per se.

[Injuneer]

Everything looks fairly normal.

Each bank of the engine is independant from the other. The O2 sensors voltage will NOT move together. Each one will "do its own thing"..... completely normal.

Not sure I see an exhaust leak. The PCM is cutting fuel slightly on both banks. Maybe cutting a shade more than the normally acceptable level of 5%. Surpisingly, an injector "drip" will cause the PCM to cut fuel. The unburned fuel leaves the cylinder, and once its in the exhaust it consumes some of the oxygen, making the O2 sensor think its running rich. So the PCM cuts fuel.

Hard to say if that is the problem. +/- 5% on the long term fuel corrections shouldn't be a cause for concern. The fact that the bank 2 long term is -7.8%, and a bit different than the bank 1 long term is a POSSIBLE indication of a problem.

[Joe K. 99 Zeee!!]

I got a lean indication in just one bank once. Apparently I hadn't gotten the intake tube all the way around the throttle body. Enough air got in that the PCM couldn't correct for it and threw a Service Engine light. For some reason, maybe positioning of the sensors, one bank will give a lean indication sooner than the other. Oh, this was in a '96 LT1 by the way.

Have you checked on the intake side??

[97LT1Z28]

I'll check it again!

When the car starts to miss badly at idle, I noticed that the exhaust smells very rich. I wonder if some plug wires are arching on that side causing the miss and unburnt fuel is coming out of the exhaust??

[Injuneer]

A misfire produces unburnt fuel and the air that wasn't consumed. The air hits the O2 sensor, and it produces a "lean" signal, so the PCM starts to add fuel, using the long term fuel corrections. That doesn't appear to be what is happening with your engine. Your long term corrections are negative, meaning the PCM is reacting to a real or false "rich" condition.

Your long terms are not really all that bad. Its the fact that the left side is a bit outside of the acceptable level, and different from the right side.

Now this could be a combination of multiple problems.... too high a fuel pressure would start to pull the long terms down, and the misfires might push them up.... but that's an extreme combination.

You need to get the long term corrections for more than Cell 16 (idle). Try and get the long term values for some low load/low rpm cells (01, 02) and for some high load/high rpm cells (14, 15), and as many others in between.

If you have a complete data log from a startup through warmup, normal driving and a WOT blast, you can probably get one of us to look at it. I'm just so backed up with logs that people send me to look at that I can't guarantee when I can get to it. But there are others here who can help.

If you have a log, I need it in ".csv" or ".xls" format.

[wrd1972]

I just got new scanning software yesterday - I'm still trying to find the low-rpm miss and rough idle problem. Here's what the program says:

At Idle in closed loop:

Manifold Absolute Pressure (in/hg) is 10.3 - 10.6
Intake Air Temp is 109 dg F
Ignition Timing Advance varied between 14 - 16 degrees
MAF Flow Rate was .86 - .89 lb/min
Long Term Fuel Trim Bank 1 was -7.8%
Long Term Fuel Trim Bank 2 was -2.3%
O2 Sensor B1S1 Voltage ranged from .12 V to .795 V
O2 Sensor B2S1 Voltage ranged from .08 V to .835 V

The Bank 1 and Bank 2 O2 Sensors didn't seem to follow one another - it seems like they each did their own thing separately.

Now I'm thinking my problem is both the front O2 sensors......

What scan software did you use?

[97LT1Z28]

The software is Tekmate 2.5.

Here's the address to their site with a description:

http://www.tekmatetools.com/

Fred, I'll do streaming diagnostics on the Long Term Fuel Trim from warm-up to idle and WOT and send you the results in .xls format. I understand if you can't get to it right away. I really respect your opinion - in my eyes, you are an "F-Body Scientist." Be sure to include that on your resume!

Thanks for your help!

[Joe 1320]

I'll check it again!

When the car starts to miss badly at idle, I noticed that the exhaust smells very rich. I wonder if some plug wires are arching on that side causing the miss and unburnt fuel is coming out of the exhaust??

Start the car in a dark environment with the hood up. If there is any voltage leak from the wires it will show as a blue glow and in some cases you can see the actual spark.

[97LT1Z28]

I did that - I was very suprised that I didn't find any voltage leak anywhere. I was so sure I'd find a leak, I used a mirror around the sides to look and still nothing.

Earlier, Fred posted a theory suggesting that I could have an injector drip or clogged injectors. It makes perfect sense! I think sending the fuel injectors in for a cleaning will be my very next step.

[97LT1Z28]

Problem Solved!

Whoo Hoo! Problem solved! I pulled my plug wires off and found that they were coroded - big time! That was so suprising since I put them on only three to four months ago! Anyway, I cleaned them up and applied some quality die-electric grease to each wire - now it runs like a champ! Rough idle is now smooth..... Low RPM miss is now completely gone! Now, on to the next problem . . . why are my rear tires smoking ? ?

[gottico2]

floorboard patterns on firebird and camaro...identical?

is the floorboard layout on camaro and firebirds identical? I am thinking about buying some finished aluminum floor plates for my bird but the place I am working with says they have them for 93-97 camaros, not firebirds...will it work?

[4THGEN Z]

Now, on to the next problem . . . why are my rear tires smoking ? ?

Thats not a problem.....that means your problems are solved, LOL

[Injuneer]

is the floorboard layout on camaro and firebirds identical? I am thinking about buying some finished aluminum floor plates for my bird but the place I am working with says they have them for 93-97 camaros, not firebirds...will it work?

Generally, its best to start a new thread for a new subject.... not a good idea to just tack it on a thread that is totally unrelated.