Hey folks, I'm having a hard time figuring out what the issue is with my moms car, it's an 89 Pontiac Trans Am GTA with a 5.7. The car has 38k miles and and is completely stock. I remember that it had the ecm replaced under warranty because of a poor running condition, if I remember correctly it's because it was stalling. The problem now is once the car is 100% warmed up it runs extremely rich, so rich I get black smoke.

I took a peak at it, saw the ect was seeping coolent and since a faulty ect can cause a rich condition I threw one at it, symptoms didn't change.

My second guess was an o2, had one left over from my car and threw it in, running condition improved slightly. Also before I threw parts at it I hooked it up to a tech l, the tech l would never get a continuous stream of information so it was worthless. I then purchased a usb/aldl cable (http://www.aldlcable.com/) to use with my laptop and it wouldn't connect. I don't know if it's because of the car or because of a fault on my end, I haven't tried it in my car yet.

And before I put any parts in it I pulled the ecm and prom to see if I could find any corrosion or anything else that would obvious, found nothing.

Only other sensor on it that controls a/f ratio is the maf and tps that seem to work perfect using a fluke meter.

So I'm at a loss, any ideas?

 

Try the simple method:
-jumper ALDL pins 1&2 (upper right)
-turn the keys On and record the SES flashes
-when you see the 2nd set of "12"s, turn off the ingition and remove jumper
Consider the coolant temp sensor in the front of the intake base. This is where the ECM sees temp; if too low it will not enter closed loop mode.
To test for closed loop mode:
-jumper ALDL pins 1&2
-start the engine and watch SES flash rate
-initially it will be 2Hz,
-after a minute or two it should drop to 1Hz, indicating closed loop mode

 

The car isn't tripping the check engine light, I tried to jump the two pins and no codes but 12 flashed.

The ect sensor that was replaced was the one for the ecm, at the base of the intake on the front of engine.

 

bad injectors maybe?

Since the O2 is only one side, failure of 1 or 2 injectors on that side can cause the ECM to compensate for what it thinks is lean. And, you get rich.

Measure resistance of injectors hot and cold. Should stay about the same (@ 15-16ohms).

 

Good thinking, I'll have to do that. I've also been thinking that maybe the coil is going out since it runs fine when it's cold and only runs like shat after it's been running for 15 mins or so.

 

I had 2 bad, car never thew a code. Ran like crap.

 

My 89 Formula with the 5.7 ran like a POS with no codes. I changed out the injectors to the bosch III from FIC and it now runs great.