Bignasty85

Ok guys so here's what I have !
I have a 94 z28 auto and have the le2 h/c package done with all the bolt ons to compensate for the kit. So here's the issue I had the pcm tuned by Jeff Creech from Carolina auto masters and the car runs good for a little while and starts acting like it's loading up but if I punch the gas pedal down it will hesitate then clear out and then go back to running rough! Please if anyone has heard of or had this issue please help or give me an idea of what it can possibly be. Thanks a lot

Injuneer

Doesn't sound like an "LE2" problem, as indicated in the topic. Sounds like a tune problem, or something in the A/F ratio control system.

Did the engine every run correctly after the tune? Or has it been a problem since day 1?

Did you ask the tuner about the problem? Did he ask you for a data log of the PCM when this problem is happening?

Is this a closed-loop tune? If so, does the problem seem to start when the PCM goes into closed loop (about 3.5 minutes from startup, coolant above 140*F and O2 sensors hot enough to work)?

Have you done basic checks, like checking for PCM codes or checking the fuel pressure?

Have you checked the rubber inlet elbow for tears, or the bottom of the elbow not being fully on the throttle body?

Has the MAF sensor been cleaned?

Bignasty85

Well it seems like it's been a problem since the tune was done and it seems like it's running rich from the way it smells! And yes about 3-4 min it starts running rough I have recently got the car done and haven't really been able to drive it to see what was going on until now and I'm not sure if it's a closed loop tune or not honestly

Injuneer

Did you ask the tuner about the problem? Did he ask you for a data log of the PCM when this problem is happening?

You can produce a data log of the PCM, showing what happens when the PCM transitions from open loop to closed loop. That's when the O2 sensors come into play. While the best person to look at the data log would be the tuner, there are a couple of us here that can look for problems in the system. I suspect Jeff is a reliable LT1 tuner, so it's important to look for problems in your setup .... faulty sensor(s), etc.

Go to the "sticky" in the "Computer Diagnostics and Tuning" forum, and look at the thread for Scan9495. Free download, you will need to buy a cable (ready made is best, the D-I-Y cables suffer from crappy Chinese made parts/quality control).

If you have problems downloading or getting it to run, the author of the software (GaryDoug) is a member here and is always willing to help.

Bignasty85

Well I told him kind of what was happening and he told me to bring it to him to see what's going on when he gave me the time I just brought him my pcm not the car itself but I think I downloaded the scan from carputing.com I tried cleaning the iac and maf earlier and it didn't help I'm petty sure it's an A/F problem or maybe to small of injectors possibly I'm running 30# I've seen a lot of people running 36-42# just gonna have to get it hooked up again and see what's going on

Injuneer

Post the carputing scan log, in .csv format, on an FTP site, so we can take a look at it.

Bignasty85

Ok I might need some help I've never done any scanning or stuff like that but I'm wanting to learn as pretty good at picking up on things pretty easy and what is ftp site ?

Injuneer

A place where you can upload files, and other can go there and download them.

I though you might already have a file, per your comments. If it makes it easier, I'll send you my e-mail address in a Private Message, and you can e-mail the file as an attachment.

Scan9495 is better than anything else.

Bignasty85

Yeah I'm new to all of this I've had a few z28's but never had one built to where I need it to be tuned and deal with all this computer stuff haha but I did have a friend use his scan tool on it today and here's what came up
18 injector circuit
33 map sensor circuit
43 knock sensor circuit
44 left O2 sensor circuit
48 MAF sensor circuit
50 system voltage low
65 right O2 sensor circuit
All codes saying circuit means maybe caused by faulty pcm
This is what he wrote down so I just put exactly what he said if tht might help

Injuneer

Was the scanner an Innova 3120?

Bignasty85

Not sure honestly it was red about 10"x14" size I can find out if it is important

Injuneer

The Innova has a faulty DTC code table for the 94/95 LT1 engines. It gives you about 8 codes, some of which aren't even valid, when in fact you have no codes at all. Your list is slightly different than what pops up on the Innova. Sounds like he may have used a Snap-On "brick".

I have the factory manual for the 94 F-Bodies, and am relatively familiar with all of the codes, having owned by 94 Formula for 21 years.

Scan9495 is the best thing to use. Gary has put a lot of work into making it the most useful scanner for the OBD-1 LT1's.... and he doesn't even have an LT1. It reads the PCM,l the EBCM and the air bag system. Nothing else can touch it in that respect. Well.... maybe the GM dealer Tech-1 or Tech-2, but if you want to go that route, Gary found a low $$$ Chinese clone of the Tech-1, and has found it to be fairly reliable.

Injuneer

The alternative is that the battery supply voltage to the PCM, which dropped low enough to set the code DTC 50 (< 8.0V) tripped all those codes, because they all rely on voltage readings.