Trying to work some bugs out of my son's '86 LG4 Firebird so we can finally get it on the road. Car has had a ton of work done to it over the past year and now that were in the home stretch, I can't seem to get the thing to run correctly. Major/important stuff we did includes:

• Carb rebuilt by Ken an Everyday performance
• New Edelbrock intake due to corrosion around coolant passages
• New timing set
• New plugs, cap, rotor
• New vacuum lines

Straight out of the box tuning with no tuning, the car started up and would hold an idle on it's own but would eventually flash a CEL for the O2 sensor. Since I don't like to randomly just replace parts, I searched for a way to see if I could verify open/closed loop and found the process for jumping A & B on the ALDL while running to put the car in field service mode where the CEL would flash differently based on open or closed loop. I did exactly that, but the CEL never flashed like it was supposed to and I immediately noticed a change in the way the car ran as soon as I jumped the pins...and I wasn't expecting that.

Now that we're trying to get the tune in better shape (had a bunch of stuff come up since then), the car just doesn't seem to want to run. It appears to be running extremely rich. We did our best to set the tps, but it was all over the place so I stuck a new one from Standard in. It reads much better now so I was expecting a difference in the way the car ran. Nope. While in closed loop, the dwell reads 30, but when the car went into open loop, it jumped to 48+ and no amount of adjustment on the idle air bleed made a difference.

I keep going back to what changed since it last ran semi-right and the only thing I can come up with is jumping that ALDL. Can anyone confirm if that's a valid test on the LG4? When I got back and review now, it seems that's mentioned mostly for the TPI cars. If that was a no-no, is there any way to look/test for damage to the ECM?

Thanks.

 

My 88 was doing some of that when I first got it. Took a while but finally figured out the main grounding point was fried. That is a bolt on the back of the passenger side head with several wires grounded there. Doesn't take much to foul up the ECM since it controls most operations by controlling the ground circuits. Check all grounds.

 

Did you make all 5 of these changes at once?
If so, then you are going to have one heck of a time figuring this out.
Always make only 1 change at a time.
Good luck to you.

 

The car was a non-runner when we got it. All those things were done to bring it back to life. The car would idle on it's own after all that was done.

Then I attempted to verify O2 sensor operation by jumping A&B in the ALDL. Seems like it that is when it stopped wanting to run.