KYWes

I've attached my datalog file from Scan 94/95.

Recent run in my '95 Z28 M6
No A/C
No EGR
No Airpump

Anybody interested in reading?

Injuneer

I'll take a look, but it might take a while.... several others in front of yours.

KYWes

Thanks, no problem. I intend on getting a dyno tune so your insights will help.

Injuneer

Quick review shows the Bank 1 (driver side) O2 is seriously screwed up. It's reading super lean, causing DTC 44 to set (Bank 1 O2 sensor lean). As a result, left side long term fuel corrections are basically maxed out at 160 (adding 25% extra fuel) and it's using the short terms to add even more.

Bank 2 (passenger side) is also messed up, with long terms bottomed out at 108 in several cells, pulling 15% fuel out on that side.

I need to spend more time looking at it, but thought you needed to know about the "split BLM's"..... in case you are aware of any issues with either of the O2 sensors, or the wiring for them.

KYWes

I wasn't sure how much the new cam with 1.6rr's and new cat back system, replacing the stock exhaust, were affecting things and that a good tune would adjust for.

I know the O2 sensors are plugged in and aren't all that old. Are you thinking that the O2 sensors may not be working right? I'll replace them if you think that might help.

I also have a pretty good miss that I was going to work on this weekend. Could the excess fuel be involved in that? I installed new AC Delco plugs this go around but am still running Taylor wires I put in a few years ago. I had thought of replacing the wires to see if that's where the miss is.

GaryDoug

Bank1 seems to go lean gradually around 450-550 seconds in. Could that be a failing injector?

Injuneer

I didn't get to look at that time area, but I will. I did notice a repeating pattern where the left BLM is at 160, and the left INT work its way up from 128 to about 201, hangs there for a bit, then the INT resets to 128 and the process repeats. As I recall, the left O2 sensor is hanging at ~50 - 60 mV, and doesn't change much in response.

bobdec

OP says he has a "good miss" a non firing cylinder will read excessively lean for that bank and confuses PCM correction for both banks after a while. Also had a thread with a couple of plug wires swapped cause it.

KYWes

I went ahead and changed the O2 sensors. The left sensor was all fouled and sooty. The right sensor was clean and had a light grey cast. SOTP feel seems better. Still have a miss and more what I would call a "breaking up" performance. That is it's performance isn't consistent. It will stumble and sputter then it will straighten out for a few seconds. Will be working on it Tuesday.

Injuneer

Run your scan again, and take a look to see if the left O2 sensor readings are better. Could also have been a wiring problem causing the sensor to hang at such a low value. The sooty O2 sensor could be pointing to a "false" lean condition, causing the PCM to add fuel it doesn't need. Not even with a pre-cat exhaust leak, or a misfire, I wouldn't expect the sensor readings to hang below 100mV.

You need to inspect the plugs for fouling.

KYWes

Is there a thread or web page that gives common values for the readings gathered on a datalog, specifically Scan94/95?

Injuneer

No.

But I have a writeup on LT1 scan readings that I wrote for "Scanmaster" more than 10 years ago. Used to be on my now defunct website. I can send you a .pdf of the file if you want.

Maybe I can work with Gary and come up with a "Scan(93)9495" version.

You can also look at the factory service manual. I only have 94 and 96 versions, but your 95 is not much different than a 94. You can download a copy of the manual on the "Fourth Generation......" forum on the Firebird Nation site. Look for a pinned post at the top of the forum, authored by Gary.

In the 94 manual, look at 6E3-A-18 for a list of everything you can scan with a GM (OTC) Tech-1 (or 2) scanner, including units of measurement, typical data values. Moving forward to 6E3-A-20, there is a detailed definition of each of the scan value, where it comes from, values, etc. That alone is a 6 page document.

I can send a .pdf copy of the 94 manual pages mentioned above, as well.

KYWes

Thanks.

I'd like your PDF. You can send it to KYWes@att.net

I think I have downloaded the '94 service manual. If not I'll get it and review the section you mentioned.

Injuneer

Sent

KYWes

Attached is a new datalog after I replaced both O2 sensors and installed a new PCMFORLESS program into my PCM. At locations 300> and 600> I accelerate up to about 75mph. From what I've understood from you guys comments this looks like better results.

I've also attached a short sound clip of me accelerating up to about 75 mph. It would correlate with the data at about 620. It is less than a minute long but if you listen close you will hear the engine breaking up as I accelerate. Let me know what you hear and think.