Hey guys, I bought a 93 Lightning as a project truck. I have gone through and overhauled a TON on the truck. Well I couldn’t get it running right when I put the engine back in. Threw a bunch of parts at it (scanner wouldn’t pull codes) Finally decided to try a new ecu and boom, night and day difference. Truck will run pretty well and shift now. I’m still having an issue starting it. It doesn’t want to start cold and it starts warm but runs weak for a second then smooths out. When I punch the throttle fast I hear a huge sucking noise from throttle body and the engine pauses for a second then idles up fine. Doesn’t do it as bad in drive. I did mess with the idle stop screw not knowing... got the engine to idle at about 600 rpm with the AIC unplugged and then haven’t touched it. Engine is backfiring a little. New map, speed density, coolant temp, tps, fpr, cap and rotor, and spark plugs. 40 psi at fuel rail and no vaccum leaks.

 

Did u check to make sure the initial timing is set to 10 degrees, with the spout connector removed, at idle? Did you put the spout connector back in?

40psi is high at idle, with an OEM regulator. Fuel pressure should be closer to 30psi, which may indicate a vacuum leak. I'd recommend putting a vacuum gauge on it.

 

I was getting about 15 hg of vac. I have timing set at 14 on purpose. I discovered that the truck will Fire right up fine when cold if I unplug the coolant temp sensor ( a new sensor). I have also tried 2 new fpr and both put 40psi to rail at idle.

 

15" of vacuum is low for idle on a bone stock motor, which is likely the reason the fuel pressure is higher. Have you been able to scan for codes since you installed the new ECU?

 

Yes, it pulled a 117. So I replaced the ect and nada.

 

If you're hearing sucking noises around the throttle body, with vacuum reading 15", you might want to look for a leak of some kind.

The timing, with it being 14* initial, with the spout connector removed, should yield 30* with the connector re-installed.