I have a 91' T/A GTA w/LB9 and a 700r4. Its idleing very rough to the point it wants to die. Above 2800rpm or so it gets it power back. While it is running it has a VERY rich smell and wants to smoke black smoke. I used a code key and couldnt get any codes so a friend brought a scanner over and it sayed it wasnt connected. I checked 3 grounds under the hood and adjusted them for a good connection and that didnt work. The grounds were 1) Firewall to Right head 2)black wire grounded to front right fender 3)black wire grounded to front left fender. I also checked the voltage on my TPS-MAPS-new O2s-IAC-etc. They all read fine. BUT....my cars been down for about 2 weeks. A week ago i pulled 2 vaccum lines off the the EGR solenoid and put them back on and it ran fine for about 2 days. Now its doing the same thing again. Hence though when i pull the vaccum line off the brake booster i get a regular idle but if i hit the gas it hessitates and "backfires" through the intake. What could this be and why isnt my ALDL working? And it does this in "open loop" mode. Will a stuck or bad EGR does this in open loop mode and when i pulled the vaccum lines off the EGR solenoid maybe that unstuck it? Please help

 

Thats exactly what an EGR issue will do. Next thing is why. EGR valve is controlled by a vacuum control solenoid driven electrically by the ECM. Pull the connector off the solenoid and start the car. If it idles OK while it's running put the plug back in, if it dies then the solenoid is being turned on by the ECM. That rules out the solenoid and the EGR valve and any debris blocking the pintle from closing. Next, drop the ECM down and leave it connected then start the car. With a screwdriver handle give the ECM a few taps in various places and see if the condition changes. I have seen the ECM do this several times, it gets a mechanical connection problem on the PC board. The fact that it won't communicate is also a hint the problem might be the ECM itself. Rule out everything else before replacing the computer.

 

Ive tryed everything with the computer. Ive taken it out took the chipi out and air dusted everything. The wire harnesses, the chip and the board. Im fixing to go and disconnect the EGR solenoid and see what that does. I have disconnected the vacumm lines to the solenoid and connected them boack while it was running. That didnt make a difference. About 4 months ago it did the same thing, but what fixed it then what taken the chip out and putting back in b/c it was loose. But what would make the ALDL not work?

 

Basically a problem with the ECM is about the only reason it won't communicate. Since messing with the prom provided some relief of the symptom what I said may make some sense. If the prom is not communicating with the data bus it may cause a similiar situation but from what you say it sounds ECM related.

 

Lets say thats that its the ecm and thats why it wont communicate. But would a stuck or bad EGR valve cause the engine problems. And also will a stuck or bad EGR valve cause it to act the way it is while its still in open loop mode?