PCM Diagnostics & Tuning - LT1 tuning issues...

Well, my '95 F-body LT1 has been missing occasionally (roughly 1/4-1/3 of the cylinders from trying to count) lately. It's not really regular, and seems to happen almost randomly (both idle and running on the road, although never at highway speeds, 55+ mph, yet).

What I've done (in the 6 mo. I've had the car...):

- Optispark (2 months ago, I believe the first one to go in, at 213,500)
- Spark Plugs and Wires (they WERE definitely original, and were completely rusted through, with the rubber boots completely gone/rotted)
- Throttle body cleaned, about 2 weeks ago
- Intake filters cleaned (SLP CAI setup) about 2 weeks ago as well
- Oil change about a month ago

I have no clue about any other maintenance, other than A/C and radiator/coolant repairs, which I have the receipts from the previous owner. It just starts idling really rough and high (about 1300-1500rpms) and triggers a CEL while it idles rough, does this for a few seconds (no more than 20 or so) then returns to normal, and the CEL goes out (kinda limits what codes it can be, as I know many codes trigger the CEL until you shut down the engine, some even require resetting/disconnecting the battery).

It just started doing this a couple days ago, at first I thought it was a one-time only deal, but then it happened several more times. Would go to a shop, but I don't know any that'll pull codes on the bastard year (OBD 1.5) in the area, and don't want to drive 50mi, and I tried a lot of shops around here. Any ideas? I have several shops in the area that'll gladly throw O2 sensors or similar (minor) repairs at the car to see if anything sticks, but they just don't have the diag. equipment for this particular car.

Thanks!
- JR @ WVU
1995 LT1, stock ... FOR NOW :devil:

EDIT> oh yeah, bought it with 208k on the odo, has 216k on it now.

Buy a cable from AKMcables and download freescan or datamaster and find out the code. Then you will have a direction to head in.

It's not "OBD1.5"...it's OBD1, just uses the new style ALDL connector and jumping 2 pins won't make it flash codes...do what flame said, buy the cable (relatively cheap) and download freescan.

It's not "OBD1.5"...it's OBD1, just uses the new style ALDL connector and jumping 2 pins won't make it flash codes...do what flame said, buy the cable (relatively cheap) and download freescan.

I use OBD 1.5 so everyone knows I'm talking about the OBD1 ECM with the OBD2 "D-style" plug. See, you knew exactly what I was talking about when I mentioned OBD 1.5 (and shops, lots of times, don't know the F-body uses the OBD2 plug with OBD1 ECM, and think they can just scan it with the OBD2 reader ...). And seeing as I'm not the only one (google "wikipedia OBD 1.5") that uses it, I'd say it's, at least, somewhat proper terminology.

I am going to get that AKM cable and freescan (for now, probably going to look at some other software later on). I'm assuming (after looking at the site) that the AKM OBD2 cable is the right one for the 1995 car, is that correct?

Thanks again for the help!
- Jake R

I use OBD 1.5 so everyone knows I'm talking about the OBD1 ECM with the OBD2 "D-style" plug. See, you knew exactly what I was talking about when I mentioned OBD 1.5 (and shops, lots of times, don't know the F-body uses the OBD2 plug with OBD1 ECM, and think they can just scan it with the OBD2 reader ...). And seeing as I'm not the only one (google "wikipedia OBD 1.5") that uses it, I'd say it's, at least, somewhat proper terminology.

I am going to get that AKM cable and freescan (for now, probably going to look at some other software later on). I'm assuming (after looking at the site) that the AKM OBD2 cable is the right one for the 1995 car, is that correct?

Thanks again for the help!
- Jake R

The AKM OBD1 cable with the OBD2 connector is the right cable for the car. I didn't know what you were talking about by what you said, I knew what you're talking about because I've tuned about 400 LT1 cars.

You do realize that 94-95 B-Bodies have the same PCM, and a 12 pin OBD1 ALDL, and still won't flash codes by jumping 2 pins right? It's an OBD1 PCM, it's an OBD1 car. If you actually read that wikipedia article (remember, wikipedia is something ANYONE can edit, including people who do not know what they're talking about), they make reference to the last OBD1 LT1 Corvettes being able to set SOME OBD2 codes...the Corvette LT1 PCM, while compatible with the F/B body (it can run them), IS different hardware than the F/B body has. OBD1.5 in that case, is specifically referring to an OBD1 PCM, that has some ability to monitor emissions and throw P related codes...the F-Body just has the ALDL port, it's an OBD1 car.