Fuel press test all fine. Scan no codes. 0.5v on tps. Battery volt and crank speed fine. Oil press and temp and idle speed fine when use starting fluid to start. Engine will restart if I shut it off and start within a min. Engine runs in closed loop. After cooling fan cycles a number of times. I run engine rpm to 1200 to 2000 and hold. Fuel press steady @ 38lbs. Engine stalls from this held rpm with 38 lbs fuel press, in under 4 min. Acts like ignition voltage lost. Try to restart, just cranks. Shot of start fluid and fires up and runs, but idles poorly for 10 to 15 sec. then smoothes out. Somehow I'm not getting a start command. And the ignition lost acts like a faulty Ignition Module when it gets hot. I will check ignition coil and distributor ranges with ohmmeter later today. Things I've done.. Replaced fuel filter, added ground straps to insure good grounding. frame to engine. engine to firewall...firewall to relays next to brake booster. Checked wire looms for damage and pinching. Used CRC, Mass Flow Sensor cleaner, left sensor screens intact. This engine has 50k. The only other things i can think of is that #7 and #8 spark plug get white ash fouled. Seven being the worst in about 1200 miles, most prevalent after switching to Valvoline oil. I will check for coolant leak on intake manifold today also. This car is not a daily driver. Any help would be appreciated. Thanks

 

Did 89 have VATS? If so, check that.

 

Yes it does. But no code 46 has been set. This vats, is it located under hood next to the brake booster, and is it 1/2'' thick and 3''x 3'' with 4 wires, pink, black, brown and white? And have a bar code sticker with the letters (HKR) on it?

 

Here is were I'm at now. I checked resistance on all the injectors...fine. Checked voltage key on, at all injectors 12.4 volts. In crank 11.6 volts. For the heck of it, I did three different ohmmeter test on the coil, all fine. Checked pickup coil wire and did ohmmeter, tested ok. Removed control module, inspected, cleaned rusty mounting screws, silicone grease applied, install new cap and rotor. Disconnected air mass sensor, tried to start, no change. Hooked everything back up, started engine with starting fluid. The scanner I'm using in an old Monitor2000. Ran through all modes. Mode 39 is Crank RPM & PPSW (pump prime switch voltage) When cranked I got no RPM reading and 13.5 volts for the PPSW. Then I jumped down to mode 1, which is RPM & Battery at EMC. When cranking I got no rpm signal & 12.2 volts at ECM. There is a RPM, in this mode when engine is running. There is a optional tuned port injection cable for my monitor 2000, but this cable adapter reads high-speed 8192 baud data. Note, when cranked the tachometer needle jumps around as it is getting a signal. Thanks Twin_Turbo I'll see if I can find it. (vats module)

 

My buddies 87 corvette wouldn't start occasionally either, starter would engage but no fuel pump. It was the VATS box, it was "partially kaput"

 

Ok, shorted injector shut down fuel system. Replaced injectors, and I replaced the mass air flow relay. Engine stumbled when I tapped on it with screwdrive. Starts and runs great!