1SWT95Z

Hello all I am looking for some help with my 1995 Z28. Here are the specifics. OBD1 with OBD 2 connection, 355 CI, comp 218/224 (xfi466 cam I think!?)30 lb injectors, 52 mm edelbrock TB with IAC hole drilled. I am having trouble with a few things. First the car has split BLMs at idle and I was working with someone on that about a year ago. The second problem is my laptop's connection to the PCM was intermittent and finally did not connect at all so I just stopped trying to datalog at all. I am planning on trying Tunerpro RT next week instead of datamaster to log the car. I will post a log if/when I get it working. Thanks for reading guys!

krowtis

I would like to know this. I also have a 1995 z28 with the crazy computer set up.

Injuneer

It's not a "crazy" computer. It's a full-blown OBD-1 PCM, identical to the one used in the 94's. While the car has a 16-pin OBD-2 style connector, communications cables are readily available. Or you can uses Shoebox's photo to jumper a 12-pin cable.

http://shbox.com/1/xraycable.jpg

Any OBD-1 tuning software will work - lt1_edit, TunerCATS, EFI live V4, Tunerpro RT5.

Scan9495 is excellent scan/data logging software. TTS Daramaster is still available as well.

If the ALDL connection is intermittent, did you check the integrity of the tan wire connected to pin 9 in your 16-pin connector?

1SWT95Z

Fred, I have not checked that wire yet. Do you know where that wire might likely have a problem? Would it be near the aldl connector or would I be chasing the problem all the way through the wire harness to the computer?

Injuneer

Hard to say. Start at the ALDL connector. Make sure the pin isn't damaged. Make sure the wire is securely attached at the back. Ditto on the PCM connector end. Beyond that, not sure how it's routed or how you could possibly check for a signal. I'll ask GaryDoug to look at this and possibly suggest a way to test the signal on the tan wire.

GaryDoug

That's a good question. So I measure it on my setup pcm. With a multimeter set to Ohms (resistance), you should get a reading of about 1000 Ohms referenced to chassis ground. The meter polarity is not important here; the leads can go either way. Do this with the ignition off and the battery disconnected.

1SWT95Z

So I should place the meter to ohms and put red(positive) to the tan wire in the aldl connector and black(neg) to any metal on the car (steering column bracing under dash etc?) Sorry I am asking such simple questions, I just want to get this figured out and diagnosed correctly.

GaryDoug

Yes. Make sure the battery is disconnected so you get an accurate reading. If it doesn't read 1000 Ohms (1K Ohms), it is open somewhere between the connector and the pcm.

1SWT95Z

Thank you guys for the info. I am planning on checking all of this out later in next week. On a seperate note, can split BLMs be corrected with tuning or does it all rely on the IAC passages in the manifold?

Injuneer

Split BLM's can result from problems with the idle provisions in an aftermarket throttle body, the tune for the cam to control the impact of excessive overlap, faulty O2 sensors or wiring, leaks in the exhaust system before the O2 sensors, misfire(s) on one bank, vacuum leak affecting one bank, etc.

Which cells have the split BLM's?

1SWT95Z

Fred, I can look at my old data from datamaster or I can rescan this weekend (i hope) with either scan9495 or Tunerpro RT. What numbers should I be looking for? When I was able to scan before my intermittent cable connection I did the following to try to fix the BLM split or even move it from right to left bank or vice versa:
I swapped O2s(same split and same side stayed rich)
I swapped 1-7 injectors with 2-8 (same result, same split and same side stayed rich). If you can look at an old datamaster file I can post it but if newer data is better I will rescan this weekend.

Injuneer

I can look at the old file. Just takes me a while sometimes, based on what else I have on my plate.

1SWT95Z

Fred, I will try uploading my last scan tonight( from about a year and a half ago). Also I tried scan9495 last night and with the cable plugged in, the program chimed at me like 3-4 times and showed a message that there was no engine sync or connection (I forgot the exact wording). It would not connect so I'm thinking I will need to check the tan wire in the aldl connector. If I find that the tan wire is bad, do you think it would have contributed to frying the PCM on a previous reflash I tried about 3 years ago?

1SWT95Z

Fred, i'm not sure how to post my scan. It's a UNI file. Is that something I can email or is there another way to insert the file on here in a post?

GaryDoug

I think this will work if you rename the file with an allowed extension (.txt), not sure

Tell us to rename this with the .uni extension