I have a 1991 trans am with a 305 TPI. It has always ran kind of weird but never like this. It used to be that i just had a rough idle and a CEL, but all i get is a code 12. But this was only on occasion, and sometimes the speedo wouldn't even work (sometimes). But most of the time it'd be fine. With time, this problem has gotten progressively worse to the point where it always runs like this, and now it won't even idle at all. The exhaust fumes are also very strong, i can smell it from the driver seat and it has cats and mufflers and whatnot, possible an exhaust leak because i have scraped a couple times, but i dont think that would cause all this trouble. I get a CEL, try to check the codes but it just keeps flashing a code 12. I have no clue what to do, my dad it might need a new distributor and rotor, spark plug wires and plugs, but i think it might be something more severe. Any help would be appreciated!

 

If you have a laptop available, even to borrow for a few minutes, I would suggest that you make up an ALDL cable. It really helps to be able to see all the information the computer is getting. Depending on what tools you have, it can cost as little as about 10 bucks.

Here's a link to how to make the cable: http://tbichips.com/cable.htm

Other than the one resistor across pins 2 and 4, I put all the electronics in a plastic project box (also from Radio Shack).

I had built a cable with all the parts in the serial connector hood, but it was a pain and it finally broke. Trust me, just throw it in a project box.

If it is beyond your skill to make, then you can buy one. http://www.aldlcable.com/

Then, grab a free copy of WinALDL. You might make a small donation.

http://winaldl.joby.se/

I just got an EBL unit for tuning. But, either way, the VERY FIRST thing anyone should do is get a cable to see all the data the computer is seeing.

That will help your troubleshooting greatly. Check the DIY PROM board for more info.

 

Thanks, I would rather make one of my own, but my laptop only has USB ports, no serial. Anyway to make one for a USB, and some insrtuctions on how to make it if so?

 

Belkin has a good USB/serial converter that works well. Instead of a simple pin-to-pin converter, it has a complete 16550 UART in the adapter, making a fully functional, fully handshaking COM port from a USB hole. They're about $45, but the repinned USB/serial adapters won't work in this type of application.

The lack of error codes may indicate a problem with ECM communications and execution.

 

I agree with Vader; "Lack of Error Codes" ECM related.
Question, have you reset the ECM?
Is a rough idle your only symptom?
Can you post a picture of your engine bay?

 

No i haven't reset the ECM, and it doesn't idle at all now, the speedo doesn't work, and it is running extremely rich, the fuel tank went down 2 little lines just from me holding the idle at 600 rpms via throttle while searching for possible leaks and such, when i floor it lots of smoke out the back. I can get a picture of my engine bay in a second

 

I have some sideview pictures also if you want to see them

 

I had thought of asking about smoke, but since it's an obvious thing I didn't.
Question is what color smoke? There are four colors of smoke white, gray, blue, black.
If it's misfiring it should be black.
I'm leaning more to gray.

 

Yea its definately gray smoke

 

any suggestions on where to start before i get this ALDL cable? probably won't be for another 2 weeks or so but i don't wanna waste time waiting for it when i could possibly fix the problem now,

here are some videos of whats going on, today it actually had an idle and is doing what it used to do, its kind of hard to explain but the idle is very rough and the CEL flashes rapidly, heres two videos of what is going on

http://www.youtube.com/watch?v=Y2L96EINigY = CEL flashing and actually idling

http://www.youtube.com/watch?v=lkOqUZcKWo8 = No idle at all

 

bump