Hey all,

Car is a 1991 'bird w/the L03 and a T5. Today, with a fresh battery in the car, I tried to get started on a brake bleeding job to try and finally drive the car again after a fair deal of other work done. The car already had some type of running rich issue before I was trying to diagnose, but now I'm having bigger issues! Here's what it's doing..

- Motor cranks fast, like a healthy motor with plenty of voltage should, but will not start without forcing it. By forcing it, I mean pouring a small amount of gas into the TBI and then cranking it up. It will start up this way, run fine, then die after running for a few minutes.

- It still runs pretty pig rich, but I'm not sure what's causing it.

- Tried to run a diagnostic on the car for some codes, but now diagnostic mode won't engage! No code 12 to indicate the system is working properly, as it would do before.

- Has sat for a little bit, but has fresh gas in the tank.

What could be causing it to do this? I'm worried maybe the ECU itself is going bad since I can't get the computer to go into diagnostic mode for trouble codes. Or maybe a fuel pump? But can fuel pumps just suddenly go bad out of nowhere?

 

What other work was done to the car?

 

are you sure you didnt unhook any wires. does the cel light come on when the key is turned on?

 

No wires/sensors are unhooked, and the CEL does come on when the key is first turned, and stays on until the motor is cranked. Normally, when I try hooking the pin key into the diagnostic port, it had no issues going into diagnostic mode, but this time, it basically acted as if the key wasn't there.

Recent work on the car includes a bunch of brake system work, basically a replacement of almost everything. Nothing to do w/anything on the engine or involving wiring/sensors.

The car has acted a bit odd before back when I was driving it. Gave me a bunch of crap one time trying to start after stopping at a gas station (not getting enough gas at first), and even though I know for sure it runs rich now, I'd get occasional cylinder misfires while idling at operating temp, and check engine lights coming on, accompanied with a noticeable loss of power when giving it more throttle, particularly on hills/freeway ramps.

The last "easy" things to check for that I can think of which I haven't done yet is to check fuel pressure, and look for vaccum leaks, but other than that, I'm pretty lost other than ECM/sensor/wiring issues I can't seem to diagnose.

 

Is the security light on? You may have a VATS issue

 

The VATS isn't the issue. It comes on, then goes away like normal. The engine cranks perfectly fine, but after doing a bit more research, I may have (hopefully!) figured it out.

I'm going to have to check the fuel pump relay/fuel pressure/look for vacuum leaks. I suspect there is a leak, because I found a missing bolt on the intake manifold. My theory is that this has been causing a leak, and the ECM is trying to compensate for that by adding more fuel, which would explain why the car has ran like crap at operating temp since owning it, and now why I'm having fuel issues (Overworked fuel pump = ruined?).

Assuming that is the issue, hopefully addressing the intake manifold and fuel delivery issues will have this L03 finally running right!